diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
new file mode 100644
index 0000000..f66e2bc
--- /dev/null
+++ b/.github/workflows/windows.yml
@@ -0,0 +1,44 @@
+name: windows
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ${{matrix.os}}
+    strategy:
+      matrix:
+        # windows-2016 and windows-2019 have MSVC 2017 and 2019 installed
+        # respectively: https://github.com/actions/virtual-environments.
+        os: [windows-2016, windows-2019]
+        platform: [Win32, x64]
+        build_type: [Debug, Release]
+        include:
+          - os: windows-2016
+            platform: Win32
+            build_type: Debug
+            shared: -DBUILD_SHARED_LIBS=ON
+        exclude:
+          - os: windows-2016
+            platform: Win32
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Create Build Environment
+      run: cmake -E make_directory ${{runner.workspace}}/build
+
+    - name: Configure
+      # Use a bash shell for $GITHUB_WORKSPACE.
+      shell: bash
+      working-directory: ${{runner.workspace}}/build
+      run: |
+        cmake -DCMAKE_BUILD_TYPE=${{matrix.build_type}} ${{matrix.shared}} \
+              -A ${{matrix.platform}} $GITHUB_WORKSPACE
+
+    - name: Build
+      working-directory: ${{runner.workspace}}/build
+      run: cmake --build . --config ${{matrix.build_type}}
+
+    - name: Test
+      working-directory: ${{runner.workspace}}/build
+      run: ctest -C ${{matrix.build_type}}
diff --git a/.gitignore b/.gitignore
index 694f8f8..e95cbaa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 .vscode/
+.vs/
 
 *.iml
 .idea/
@@ -14,6 +15,7 @@
 /CMakeScripts
 /doc/doxyxml
 /doc/html
+/doc/node_modules
 virtualenv
 /Testing
 /install_manifest.txt
diff --git a/Android.bp b/Android.bp
index 294bb94..b5341cf 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,27 +1,69 @@
+package {
+    default_applicable_licenses: ["external_fmtlib_license"],
+}
+
+// Added automatically by a large-scale-change that took the approach of
+// 'apply every license found to every target'. While this makes sure we respect
+// every license restriction, it may not be entirely correct.
+//
+// e.g. GPL in an MIT project might only apply to the contrib/ directory.
+//
+// Please consider splitting the single license below into multiple licenses,
+// taking care not to lose any license_kind information, and overriding the
+// default license using the 'licenses: [...]' property on targets as needed.
+//
+// For unused files, consider creating a 'fileGroup' with "//visibility:private"
+// to attach the license to, and including a comment whether the files may be
+// used in the current project.
+//
+// large-scale-change included anything that looked like it might be a license
+// text as a license_text. e.g. LICENSE, NOTICE, COPYING etc.
+//
+// Please consider removing redundant or irrelevant files from 'license_text:'.
+// See: http://go/android-license-faq
+license {
+    name: "external_fmtlib_license",
+    visibility: [":__subpackages__"],
+    license_kinds: [
+        "SPDX-license-identifier-BSD",
+        "SPDX-license-identifier-CC0-1.0",
+        "SPDX-license-identifier-MIT",
+        "SPDX-license-identifier-PSF-2.0",
+        "legacy_unencumbered",
+    ],
+    license_text: [
+        "LICENSE.rst",
+        "NOTICE",
+    ],
+}
+
 cc_defaults {
-    name: "fmtlib-defaults",
-    srcs: ["src/format.cc"],
+    name: "fmtlib-non-test-defaults",
     cflags: [
         "-fno-exceptions",
-        "-Wall",
-        "-Werror",
         // If built without exceptions, libfmt uses assert.
+        // The tests *require* exceptions, so we can't win here.
+        // (This is also why we have two cc_defaults in this file.)
+        // Unless proven to be a bad idea, let's at least have some run-time
+        // checking.
         "-UNDEBUG",
     ],
-    sanitize: {
-        misc_undefined: ["integer"],
-    },
+    srcs: ["src/format.cc"],
     local_include_dirs: ["include"],
     export_include_dirs: ["include"],
+    visibility: ["//system/libbase"],
     min_sdk_version: "29",
 }
 
 // This is built into libbase.  If you want to use this library, link to libbase instead.
 cc_library_static {
     name: "fmtlib",
-    defaults: ["fmtlib-defaults"],
+    defaults: ["fmtlib-non-test-defaults"],
+
     vendor_available: true,
+    product_available: true,
     ramdisk_available: true,
+    vendor_ramdisk_available: true,
     recovery_available: true,
     host_supported: true,
     native_bridge_supported: true,
@@ -41,7 +83,60 @@
 
 cc_library_static {
     name: "fmtlib_ndk",
-    defaults: ["fmtlib-defaults"],
+    defaults: ["fmtlib-non-test-defaults"],
     sdk_version: "current",
     stl: "c++_static",
 }
+
+cc_defaults {
+    name: "fmtlib-test-defaults",
+    srcs: [
+        "src/format.cc",
+        "src/os.cc",
+        "test/gtest-extra.cc",
+        "test/util.cc",
+    ],
+    local_include_dirs: ["include"],
+    host_supported: true,
+    test_suites: ["general-tests"],
+    // The tests require exceptions and RTTI.
+    cflags: ["-fexceptions"],
+    rtti: true,
+    // The usual "gtest *and* gmock, please" dance...
+    gtest: false,
+    include_dirs: [
+        "external/googletest/googlemock/include/gmock",
+        "external/googletest/googletest/include/gtest",
+    ],
+    static_libs: [
+        "libgmock",
+        "libgtest",
+        "libgtest_main",
+    ],
+}
+
+// Most of the fmtlib tests.
+cc_test {
+    name: "fmtlib_test",
+    defaults: ["fmtlib-test-defaults"],
+    srcs: [
+        "test/chrono-test.cc",
+        "test/color-test.cc",
+        "test/core-test.cc",
+        "test/format-test.cc",
+        // Some of the os-test tests deliberately try to do bad things with
+        // file descriptors, but Android's fdsan won't let them.
+        // "test/os-test.cc",
+        "test/printf-test.cc",
+        "test/ranges-test.cc",
+        "test/scan-test.cc",
+    ],
+}
+
+// This one needs to be separate because some of the test names overlap with
+// other tests.
+cc_test {
+    name: "fmtlib_ostream_test",
+    defaults: ["fmtlib-test-defaults"],
+    srcs: ["test/ostream-test.cc"],
+}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0a17358..f21cf45 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,10 +1,8 @@
-cmake_minimum_required(VERSION 3.1.0)
+cmake_minimum_required(VERSION 3.1...3.18)
 
-# Use newer policies if available, up to most recent tested version of CMake.
-if(${CMAKE_VERSION} VERSION_LESS 3.11)
+# Fallback for using newer policies on CMake <3.12.
+if(${CMAKE_VERSION} VERSION_LESS 3.12)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.11)
 endif()
 
 # Determine if fmt is built as a subproject (using add_subdirectory)
@@ -24,15 +22,40 @@
   set(${result_var} "${result}" PARENT_SCOPE)
 endfunction()
 
+include(CMakeParseArguments)
+
+# Sets a cache variable with a docstring joined from multiple arguments:
+#   set(<variable> <value>... CACHE <type> <docstring>...)
+# This allows splitting a long docstring for readability.
+function(set_verbose)
+  # cmake_parse_arguments is broken in CMake 3.4 (cannot parse CACHE) so use
+  # list instead.
+  list(GET ARGN 0 var)
+  list(REMOVE_AT ARGN 0)
+  list(GET ARGN 0 val)
+  list(REMOVE_AT ARGN 0)
+  list(REMOVE_AT ARGN 0)
+  list(GET ARGN 0 type)
+  list(REMOVE_AT ARGN 0)
+  join(doc ${ARGN})
+  set(${var} ${val} CACHE ${type} ${doc})
+endfunction()
+
 # Set the default CMAKE_BUILD_TYPE to Release.
 # This should be done before the project command since the latter can set
 # CMAKE_BUILD_TYPE itself (it does so for nmake).
 if (MASTER_PROJECT AND NOT CMAKE_BUILD_TYPE)
-  join(doc "Choose the type of build, options are: None(CMAKE_CXX_FLAGS or "
-           "CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.")
-  set(CMAKE_BUILD_TYPE Release CACHE STRING ${doc})
+  set_verbose(CMAKE_BUILD_TYPE Release CACHE STRING
+              "Choose the type of build, options are: None(CMAKE_CXX_FLAGS or "
+              "CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.")
 endif ()
 
+project(FMT CXX)
+include(GNUInstallDirs)
+set_verbose(FMT_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR} CACHE STRING
+            "Installation directory for include files, a relative path that "
+            "will be joined with ${CMAKE_INSTALL_PREFIX} or an absolute path.")
+
 option(FMT_PEDANTIC "Enable extra warnings and expensive tests." OFF)
 option(FMT_WERROR "Halt the compilation with an error on compiler warnings."
        OFF)
@@ -42,8 +65,8 @@
 option(FMT_INSTALL "Generate the install target." ${MASTER_PROJECT})
 option(FMT_TEST "Generate the test target." ${MASTER_PROJECT})
 option(FMT_FUZZ "Generate the fuzz target." OFF)
-
-project(FMT CXX)
+option(FMT_CUDA_TEST "Generate the cuda-test target." OFF)
+option(FMT_OS "Include core requiring OS (Windows/Posix) " ON)
 
 # Get version from core.h
 file(READ include/fmt/core.h core_h)
@@ -60,26 +83,35 @@
 
 message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")
 
-set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+if (NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
+  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+endif ()
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
   "${CMAKE_CURRENT_SOURCE_DIR}/support/cmake")
 
 include(cxx14)
 include(CheckCXXCompilerFlag)
+include(JoinPaths)
 
-set(FMT_REQUIRED_FEATURES cxx_auto_type cxx_variadic_templates)
+list(FIND CMAKE_CXX_COMPILE_FEATURES "cxx_variadic_templates" index)
+if (${index} GREATER -1)
+  # Use cxx_variadic_templates instead of more appropriate cxx_std_11 for
+  # compatibility with older CMake versions.
+  set(FMT_REQUIRED_FEATURES cxx_variadic_templates)
+endif ()
+message(STATUS "Required features: ${FMT_REQUIRED_FEATURES}")
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
   set(PEDANTIC_COMPILE_FLAGS -pedantic-errors -Wall -Wextra -pedantic
       -Wold-style-cast -Wundef
       -Wredundant-decls -Wwrite-strings -Wpointer-arith
       -Wcast-qual -Wformat=2 -Wmissing-include-dirs
-      -Wcast-align -Wnon-virtual-dtor
+      -Wcast-align
       -Wctor-dtor-privacy -Wdisabled-optimization
       -Winvalid-pch -Woverloaded-virtual
-      -Wconversion -Wswitch-enum
-      -Wno-ctor-dtor-privacy -Wno-format-nonliteral -Wno-shadow)
+      -Wconversion -Wswitch-enum -Wundef
+      -Wno-ctor-dtor-privacy -Wno-format-nonliteral)
   if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.6)
       set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS} -Wnoexcept
          -Wno-dangling-else -Wno-unused-local-typedefs)
@@ -97,8 +129,8 @@
 endif ()
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-  set(PEDANTIC_COMPILE_FLAGS -Wall -Wextra -pedantic -Wconversion
-      -Wno-sign-conversion -Wdeprecated -Wweak-vtables)
+  set(PEDANTIC_COMPILE_FLAGS -Wall -Wextra -pedantic -Wconversion -Wundef
+      -Wdeprecated -Wweak-vtables)
   check_cxx_compiler_flag(-Wzero-as-null-pointer-constant HAS_NULLPTR_WARNING)
   if (HAS_NULLPTR_WARNING)
     set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS}
@@ -122,7 +154,9 @@
     set(MSBUILD_SETUP "call \"${WINSDK_SETENV}\"")
   endif ()
   # Set FrameworkPathOverride to get rid of MSB3644 warnings.
-  set(netfxpath "C:\\Program Files\\Reference Assemblies\\Microsoft\\Framework\\.NETFramework\\v4.0")
+  join(netfxpath
+       "C:\\Program Files\\Reference Assemblies\\Microsoft\\Framework\\"
+       ".NETFramework\\v4.0")
   file(WRITE run-msbuild.bat "
     ${MSBUILD_SETUP}
     ${CMAKE_MAKE_PROGRAM} -p:FrameworkPathOverride=\"${netfxpath}\" %*")
@@ -150,8 +184,12 @@
 
 # Define the fmt library, its includes and the needed defines.
 add_headers(FMT_HEADERS chrono.h color.h compile.h core.h format.h format-inl.h
-                        locale.h ostream.h posix.h printf.h ranges.h)
-set(FMT_SOURCES src/format.cc src/posix.cc)
+                        locale.h os.h ostream.h posix.h printf.h ranges.h)
+if (FMT_OS)
+  set(FMT_SOURCES src/format.cc src/os.cc)
+else()
+  set(FMT_SOURCES src/format.cc)
+endif ()
 
 add_library(fmt ${FMT_SOURCES} ${FMT_HEADERS} README.rst ChangeLog.rst)
 add_library(fmt::fmt ALIAS fmt)
@@ -160,6 +198,13 @@
   target_compile_definitions(fmt PUBLIC FMT_LOCALE)
 endif ()
 
+if (MINGW)
+  check_cxx_compiler_flag("Wa,-mbig-obj" FMT_HAS_MBIG_OBJ)
+  if (${FMT_HAS_MBIG_OBJ})
+    target_compile_options(fmt PUBLIC "-Wa,-mbig-obj")
+  endif()
+endif ()
+
 if (FMT_WERROR)
   target_compile_options(fmt PRIVATE ${WERROR_FLAG})
 endif ()
@@ -171,14 +216,24 @@
 
 target_include_directories(fmt PUBLIC
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
+
+set(FMT_DEBUG_POSTFIX d CACHE STRING "Debug library postfix.")
 
 set_target_properties(fmt PROPERTIES
   VERSION ${FMT_VERSION} SOVERSION ${CPACK_PACKAGE_VERSION_MAJOR}
-  DEBUG_POSTFIX d)
+  DEBUG_POSTFIX "${FMT_DEBUG_POSTFIX}")
+
+# Set FMT_LIB_NAME for pkg-config fmt.pc. We cannot use the OUTPUT_NAME target
+# property because it's not set by default.
+set(FMT_LIB_NAME fmt)
+if (CMAKE_BUILD_TYPE STREQUAL "Debug")
+  set(FMT_LIB_NAME ${FMT_LIB_NAME}${FMT_DEBUG_POSTFIX})
+endif ()
 
 if (BUILD_SHARED_LIBS)
-  if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+  if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS" AND
+      NOT EMSCRIPTEN)
     # Fix rpmlint warning:
     # unused-direct-shlib-dependency /usr/lib/libformat.so.1.1.0 /lib/libm.so.6.
     target_link_libraries(fmt -Wl,--as-needed)
@@ -193,43 +248,42 @@
 add_library(fmt::fmt-header-only ALIAS fmt-header-only)
 
 target_compile_definitions(fmt-header-only INTERFACE FMT_HEADER_ONLY=1)
-
 target_compile_features(fmt-header-only INTERFACE ${FMT_REQUIRED_FEATURES})
 
 target_include_directories(fmt-header-only INTERFACE
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
 # Install targets.
 if (FMT_INSTALL)
-  include(GNUInstallDirs)
   include(CMakePackageConfigHelpers)
-  set(FMT_CMAKE_DIR ${CMAKE_INSTALL_LIBDIR}/cmake/fmt CACHE STRING
-      "Installation directory for cmake files, relative to ${CMAKE_INSTALL_PREFIX}.")
+  set_verbose(FMT_CMAKE_DIR ${CMAKE_INSTALL_LIBDIR}/cmake/fmt CACHE STRING
+              "Installation directory for cmake files, a relative path that "
+              "will be joined with ${CMAKE_INSTALL_PREFIX} or an absolute "
+              "path.")
   set(version_config ${PROJECT_BINARY_DIR}/fmt-config-version.cmake)
   set(project_config ${PROJECT_BINARY_DIR}/fmt-config.cmake)
   set(pkgconfig ${PROJECT_BINARY_DIR}/fmt.pc)
   set(targets_export_name fmt-targets)
 
-  set (INSTALL_TARGETS fmt)
-  if (TARGET fmt-header-only)
-    set(INSTALL_TARGETS ${INSTALL_TARGETS} fmt-header-only)
-  endif ()
+  set_verbose(FMT_LIB_DIR ${CMAKE_INSTALL_LIBDIR} CACHE STRING
+              "Installation directory for libraries, a relative path that "
+              "will be joined to ${CMAKE_INSTALL_PREFIX} or an absolute path.")
 
-  set(FMT_LIB_DIR ${CMAKE_INSTALL_LIBDIR} CACHE STRING
-      "Installation directory for libraries, relative to ${CMAKE_INSTALL_PREFIX}.")
-
-  set(FMT_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR}/fmt CACHE STRING
-      "Installation directory for include files, relative to ${CMAKE_INSTALL_PREFIX}.")
-
-  set(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE PATH
-      "Installation directory for pkgconfig (.pc) files, relative to ${CMAKE_INSTALL_PREFIX}.")
+  set_verbose(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE PATH
+              "Installation directory for pkgconfig (.pc) files, a relative "
+              "path that will be joined with ${CMAKE_INSTALL_PREFIX} or an "
+              "absolute path.")
 
   # Generate the version, config and target files into the build directory.
   write_basic_package_version_file(
     ${version_config}
     VERSION ${FMT_VERSION}
     COMPATIBILITY AnyNewerVersion)
+
+  join_paths(libdir_for_pc_file "\${exec_prefix}" "${FMT_LIB_DIR}")
+  join_paths(includedir_for_pc_file "\${prefix}" "${FMT_INC_DIR}")
+
   configure_file(
     "${PROJECT_SOURCE_DIR}/support/cmake/fmt.pc.in"
     "${pkgconfig}"
@@ -238,6 +292,8 @@
     ${PROJECT_SOURCE_DIR}/support/cmake/fmt-config.cmake.in
     ${project_config}
     INSTALL_DESTINATION ${FMT_CMAKE_DIR})
+
+  set(INSTALL_TARGETS fmt fmt-header-only)
   # Use a namespace because CMake provides better diagnostics for namespaced
   # imported targets.
   export(TARGETS ${INSTALL_TARGETS} NAMESPACE fmt::
@@ -258,7 +314,7 @@
 
   install(FILES $<TARGET_PDB_FILE:${INSTALL_TARGETS}>
           DESTINATION ${FMT_LIB_DIR} OPTIONAL)
-  install(FILES ${FMT_HEADERS} DESTINATION ${FMT_INC_DIR})
+  install(FILES ${FMT_HEADERS} DESTINATION "${FMT_INC_DIR}/fmt")
   install(FILES "${pkgconfig}" DESTINATION "${FMT_PKGCONFIG_DIR}")
 endif ()
 
@@ -274,13 +330,20 @@
 # Control fuzzing independent of the unit tests.
 if (FMT_FUZZ)
   add_subdirectory(test/fuzzing)
+
+  # The FMT_FUZZ macro is used to prevent resource exhaustion in fuzzing
+  # mode and make fuzzing practically possible. It is similar to
+  # FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION but uses a different name to
+  # avoid interfering with fuzzing of projects that use {fmt}.
+  # See also https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode.
+  target_compile_definitions(fmt PUBLIC FMT_FUZZ)
 endif ()
 
 set(gitignore ${PROJECT_SOURCE_DIR}/.gitignore)
 if (MASTER_PROJECT AND EXISTS ${gitignore})
   # Get the list of ignored files from .gitignore.
   file (STRINGS ${gitignore} lines)
-  LIST(REMOVE_ITEM lines /doc/html)
+  list(REMOVE_ITEM lines /doc/html)
   foreach (line ${lines})
     string(REPLACE "." "[.]" line "${line}")
     string(REPLACE "*" ".*" line "${line}")
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 3532bd1..b82f145 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -14,4 +14,7 @@
 * snake_case should be used instead of UpperCamelCase for function and type
   names
 
+All documentation must adhere to the [Google Developer Documentation Style
+Guide](https://developers.google.com/style).
+
 Thanks for contributing!
diff --git a/ChangeLog.rst b/ChangeLog.rst
index dd71241..9c171af 100644
--- a/ChangeLog.rst
+++ b/ChangeLog.rst
@@ -1,3 +1,1003 @@
+7.1.3 - 2020-11-24
+------------------
+
+* Fixed handling of buffer boundaries in ``format_to_n``
+  (`#1996 <https://github.com/fmtlib/fmt/issues/1996>`_,
+  `#2029 <https://github.com/fmtlib/fmt/issues/2029>`_).
+
+* Fixed linkage errors when linking with a shared library
+  (`#2011 <https://github.com/fmtlib/fmt/issues/2011>`_).
+
+* Reintroduced ostream support to range formatters
+  (`#2014 <https://github.com/fmtlib/fmt/issues/2014>`_).
+
+* Worked around an issue with mixing std versions in gcc
+  (`#2017 <https://github.com/fmtlib/fmt/issues/2017>`_).
+
+7.1.2 - 2020-11-04
+------------------
+
+* Fixed floating point formatting with large precision
+  (`#1976 <https://github.com/fmtlib/fmt/issues/1976>`_).
+
+7.1.1 - 2020-11-01
+------------------
+
+* Fixed ABI compatibility with 7.0.x
+  (`#1961 <https://github.com/fmtlib/fmt/issues/1961>`_).
+
+* Added the ``FMT_ARM_ABI_COMPATIBILITY`` macro to work around ABI
+  incompatibility between GCC and Clang on ARM
+  (`#1919 <https://github.com/fmtlib/fmt/issues/1919>`_).
+
+* Worked around a SFINAE bug in GCC 8
+  (`#1957 <https://github.com/fmtlib/fmt/issues/1957>`_).
+
+* Fixed linkage errors when building with GCC's LTO
+  (`#1955 <https://github.com/fmtlib/fmt/issues/1955>`_).
+
+* Fixed a compilation error when building without ``__builtin_clz`` or equivalent
+  (`#1968 <https://github.com/fmtlib/fmt/pull/1968>`_).
+  Thanks `@tohammer (Tobias Hammer) <https://github.com/tohammer>`_.
+
+* Fixed a sign conversion warning
+  (`#1964 <https://github.com/fmtlib/fmt/pull/1964>`_).
+  Thanks `@OptoCloud <https://github.com/OptoCloud>`_.
+
+7.1.0 - 2020-10-25
+------------------
+
+* Switched from `Grisu3
+  <https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf>`_
+  to `Dragonbox <https://github.com/jk-jeon/dragonbox>`_ for the default
+  floating-point formatting which gives the shortest decimal representation
+  with round-trip guarantee and correct rounding
+  (`#1882 <https://github.com/fmtlib/fmt/pull/1882>`_,
+  `#1887 <https://github.com/fmtlib/fmt/pull/1887>`_,
+  `#1894 <https://github.com/fmtlib/fmt/pull/1894>`_). This makes {fmt} up to
+  20-30x faster than common implementations of ``std::ostringstream`` and
+  ``sprintf`` on `dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>`_
+  and faster than double-conversion and Ryū:
+
+  .. image:: https://user-images.githubusercontent.com/576385/
+             95684665-11719600-0ba8-11eb-8e5b-972ff4e49428.png
+
+  It is possible to get even better performance at the cost of larger binary
+  size by compiling with the ``FMT_USE_FULL_CACHE_DRAGONBOX`` macro set to 1.
+
+  Thanks `@jk-jeon (Junekey Jeon) <https://github.com/jk-jeon>`_.
+
+* Added an experimental unsynchronized file output API which, together with
+  `format string compilation <https://fmt.dev/latest/api.html#compile-api>`_,
+  can give `5-9 times speed up compared to fprintf
+  <https://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html>`_
+  on common platforms (`godbolt <https://godbolt.org/z/nsTcG8>`__):
+
+  .. code:: c++
+
+     #include <fmt/os.h>
+
+     int main() {
+       auto f = fmt::output_file("guide");
+       f.print("The answer is {}.", 42);
+     }
+
+* Added a formatter for ``std::chrono::time_point<system_clock>``
+  (`#1819 <https://github.com/fmtlib/fmt/issues/1819>`_,
+  `#1837 <https://github.com/fmtlib/fmt/pull/1837>`_). For example
+  (`godbolt <https://godbolt.org/z/c4M6fh>`__):
+
+  .. code:: c++
+
+     #include <fmt/chrono.h>
+
+     int main() {
+       auto now = std::chrono::system_clock::now();
+       fmt::print("The time is {:%H:%M:%S}.\n", now);
+     }
+
+  Thanks `@adamburgess (Adam Burgess) <https://github.com/adamburgess>`_.
+
+* Added support for ranges with non-const ``begin``/``end`` to ``fmt::join``
+  (`#1784 <https://github.com/fmtlib/fmt/issues/1784>`_,
+  `#1786 <https://github.com/fmtlib/fmt/pull/1786>`_). For example
+  (`godbolt <https://godbolt.org/z/jP63Tv>`__):
+
+  .. code:: c++
+
+     #include <fmt/ranges.h>
+     #include <range/v3/view/filter.hpp>
+
+     int main() {
+       using std::literals::string_literals::operator""s;
+       auto strs = std::array{"a"s, "bb"s, "ccc"s};
+       auto range = strs | ranges::views::filter(
+         [] (const std::string &x) { return x.size() != 2; }
+       );
+       fmt::print("{}\n", fmt::join(range, ""));
+     }
+
+  prints "accc".
+
+  Thanks `@tonyelewis (Tony E Lewis) <https://github.com/tonyelewis>`_.
+
+* Added a ``memory_buffer::append`` overload that takes a range
+  (`#1806 <https://github.com/fmtlib/fmt/pull/1806>`_).
+  Thanks `@BRevzin (Barry Revzin) <https://github.com/BRevzin>`_.
+
+* Improved handling of single code units in ``FMT_COMPILE``. For example:
+
+  .. code:: c++
+
+     #include <fmt/compile.h>
+
+     char* f(char* buf) {
+       return fmt::format_to(buf, FMT_COMPILE("x{}"), 42);
+     }
+
+  compiles to just (`godbolt <https://godbolt.org/z/5vncz3>`__):
+
+  .. code:: asm
+
+     _Z1fPc:
+       movb $120, (%rdi)
+       xorl %edx, %edx
+       cmpl $42, _ZN3fmt2v76detail10basic_dataIvE23zero_or_powers_of_10_32E+8(%rip)
+       movl $3, %eax
+       seta %dl
+       subl %edx, %eax
+       movzwl _ZN3fmt2v76detail10basic_dataIvE6digitsE+84(%rip), %edx
+       cltq
+       addq %rdi, %rax
+       movw %dx, -2(%rax)
+       ret
+
+  Here a single ``mov`` instruction writes ``'x'`` (``$120``) to the output
+  buffer.
+
+* Added dynamic width support to format string compilation
+  (`#1809 <https://github.com/fmtlib/fmt/issues/1809>`_).
+
+* Improved error reporting for unformattable types: now you'll get the type name
+  directly in the error message instead of the note:
+
+  .. code:: c++
+
+     #include <fmt/core.h>
+
+     struct how_about_no {};
+
+     int main() {
+       fmt::print("{}", how_about_no());
+     }
+
+  Error (`godbolt <https://godbolt.org/z/GoxM4e>`__):
+
+  ``fmt/core.h:1438:3: error: static_assert failed due to requirement
+  'fmt::v7::formattable<how_about_no>()' "Cannot format an argument.
+  To make type T formattable provide a formatter<T> specialization:
+  https://fmt.dev/latest/api.html#udt"
+  ...``
+
+* Added the `make_args_checked <https://fmt.dev/7.1.0/api.html#argument-lists>`_
+  function template that allows you to write formatting functions with
+  compile-time format string checks and avoid binary code bloat
+  (`godbolt <https://godbolt.org/z/PEf9qr>`__):
+
+  .. code:: c++
+
+     void vlog(const char* file, int line, fmt::string_view format,
+               fmt::format_args args) {
+       fmt::print("{}: {}: ", file, line);
+       fmt::vprint(format, args);
+     }
+
+     template <typename S, typename... Args>
+     void log(const char* file, int line, const S& format, Args&&... args) {
+       vlog(file, line, format,
+           fmt::make_args_checked<Args...>(format, args...));
+     }
+
+     #define MY_LOG(format, ...) \
+       log(__FILE__, __LINE__, FMT_STRING(format), __VA_ARGS__)
+
+     MY_LOG("invalid squishiness: {}", 42);
+
+* Replaced ``snprintf`` fallback with a faster internal IEEE 754 ``float`` and
+  ``double`` formatter for arbitrary precision. For example
+  (`godbolt <https://godbolt.org/z/dPhWvj>`__):
+
+  .. code:: c++
+
+     #include <fmt/core.h>
+
+     int main() {
+       fmt::print("{:.500}\n", 4.9406564584124654E-324);
+     }
+
+  prints
+
+  ``4.9406564584124654417656879286822137236505980261432476442558568250067550727020875186529983636163599237979656469544571773092665671035593979639877479601078187812630071319031140452784581716784898210368871863605699873072305000638740915356498438731247339727316961514003171538539807412623856559117102665855668676818703956031062493194527159149245532930545654440112748012970999954193198940908041656332452475714786901472678015935523861155013480352649347201937902681071074917033322268447533357208324319360923829e-324``.
+
+* Made ``format_to_n`` and ``formatted_size`` part of the `core API
+  <https://fmt.dev/latest/api.html#core-api>`__
+  (`godbolt <https://godbolt.org/z/sPjY1K>`__):
+
+  .. code:: c++
+
+     #include <fmt/core.h>
+
+     int main() {
+       char buffer[10];
+       auto result = fmt::format_to_n(buffer, sizeof(buffer), "{}", 42);
+     }
+
+* Added ``fmt::format_to_n`` overload with format string compilation
+  (`#1764 <https://github.com/fmtlib/fmt/issues/1764>`_,
+  `#1767 <https://github.com/fmtlib/fmt/pull/1767>`_,
+  `#1869 <https://github.com/fmtlib/fmt/pull/1869>`_). For example
+  (`godbolt <https://godbolt.org/z/93h86q>`__):
+
+  .. code:: c++
+
+     #include <fmt/compile.h>
+
+     int main() {
+       char buffer[8];
+       fmt::format_to_n(buffer, sizeof(buffer), FMT_COMPILE("{}"), 42);
+     }
+
+  Thanks `@Kurkin (Dmitry Kurkin) <https://github.com/Kurkin>`_,
+  `@alexezeder (Alexey Ochapov) <https://github.com/alexezeder>`_.
+
+* Added ``fmt::format_to`` overload that take ``text_style``
+  (`#1593 <https://github.com/fmtlib/fmt/issues/1593>`_,
+  `#1842 <https://github.com/fmtlib/fmt/issues/1842>`_,
+  `#1843 <https://github.com/fmtlib/fmt/pull/1843>`_). For example
+  (`godbolt <https://godbolt.org/z/91153r>`__):
+
+  .. code:: c++
+
+     #include <fmt/color.h>
+
+     int main() {
+       std::string out;
+       fmt::format_to(std::back_inserter(out),
+                      fmt::emphasis::bold | fg(fmt::color::red),
+                      "The answer is {}.", 42);
+     }
+
+  Thanks `@Naios (Denis Blank) <https://github.com/Naios>`_.
+
+* Made the ``#`` specifier emit trailing zeros in addition to the decimal point
+  (`#1797 <https://github.com/fmtlib/fmt/issues/1797>`_). For example
+  (`godbolt <https://godbolt.org/z/bhdcW9>`__):
+
+  .. code:: c++
+
+     #include <fmt/core.h>
+
+     int main() {
+       fmt::print("{:#.2g}", 0.5);
+     }
+
+  prints ``0.50``.
+
+* Changed the default floating point format to not include ``.0`` for
+  consistency with ``std::format`` and ``std::to_chars``
+  (`#1893 <https://github.com/fmtlib/fmt/issues/1893>`_,
+  `#1943 <https://github.com/fmtlib/fmt/issues/1943>`_). It is possible to get
+  the decimal point and trailing zero with the ``#`` specifier.
+
+* Fixed an issue with floating-point formatting that could result in addition of
+  a non-significant trailing zero in rare cases e.g. ``1.00e-34`` instead of
+  ``1.0e-34`` (`#1873 <https://github.com/fmtlib/fmt/issues/1873>`_,
+  `#1917 <https://github.com/fmtlib/fmt/issues/1917>`_).
+
+* Made ``fmt::to_string`` fallback on ``ostream`` insertion operator if
+  the ``formatter`` specialization is not provided
+  (`#1815 <https://github.com/fmtlib/fmt/issues/1815>`_,
+  `#1829 <https://github.com/fmtlib/fmt/pull/1829>`_).
+  Thanks `@alexezeder (Alexey Ochapov) <https://github.com/alexezeder>`_.
+
+* Added support for the append mode to the experimental file API and
+  improved ``fcntl.h`` detection.
+  (`#1847 <https://github.com/fmtlib/fmt/pull/1847>`_,
+  `#1848 <https://github.com/fmtlib/fmt/pull/1848>`_).
+  Thanks `@t-wiser <https://github.com/t-wiser>`_.
+
+* Fixed handling of types that have both an implicit conversion operator and
+  an overloaded ``ostream`` insertion operator
+  (`#1766 <https://github.com/fmtlib/fmt/issues/1766>`_).
+
+* Fixed a slicing issue in an internal iterator type
+  (`#1822 <https://github.com/fmtlib/fmt/pull/1822>`_).
+  Thanks `@BRevzin (Barry Revzin) <https://github.com/BRevzin>`_.
+
+* Fixed an issue in locale-specific integer formatting
+  (`#1927 <https://github.com/fmtlib/fmt/issues/1927>`_).
+
+* Fixed handling of exotic code unit types
+  (`#1870 <https://github.com/fmtlib/fmt/issues/1870>`_,
+  `#1932 <https://github.com/fmtlib/fmt/issues/1932>`_).
+
+* Improved ``FMT_ALWAYS_INLINE``
+  (`#1878 <https://github.com/fmtlib/fmt/pull/1878>`_).
+  Thanks `@jk-jeon (Junekey Jeon) <https://github.com/jk-jeon>`_.
+
+* Removed dependency on ``windows.h``
+  (`#1900 <https://github.com/fmtlib/fmt/pull/1900>`_).
+  Thanks `@bernd5 (Bernd Baumanns) <https://github.com/bernd5>`_.
+
+* Optimized counting of decimal digits on MSVC
+  (`#1890 <https://github.com/fmtlib/fmt/pull/1890>`_).
+  Thanks `@mwinterb <https://github.com/mwinterb>`_.
+
+* Improved documentation
+  (`#1772 <https://github.com/fmtlib/fmt/issues/1772>`_,
+  `#1775 <https://github.com/fmtlib/fmt/pull/1775>`_,
+  `#1792 <https://github.com/fmtlib/fmt/pull/1792>`_,
+  `#1838 <https://github.com/fmtlib/fmt/pull/1838>`_,
+  `#1888 <https://github.com/fmtlib/fmt/pull/1888>`_,
+  `#1918 <https://github.com/fmtlib/fmt/pull/1918>`_,
+  `#1939 <https://github.com/fmtlib/fmt/pull/1939>`_).
+  Thanks `@leolchat (Léonard Gérard) <https://github.com/leolchat>`_,
+  `@pepsiman (Malcolm Parsons) <https://github.com/pepsiman>`_,
+  `@Klaim (Joël Lamotte) <https://github.com/Klaim>`_,
+  `@ravijanjam (Ravi J) <https://github.com/ravijanjam>`_,
+  `@francesco-st <https://github.com/francesco-st>`_,
+  `@udnaan (Adnan) <https://github.com/udnaan>`_.
+
+* Added the ``FMT_REDUCE_INT_INSTANTIATIONS`` CMake option that reduces the
+  binary code size at the cost of some integer formatting performance. This can
+  be useful for extremely memory-constrained embedded systems
+  (`#1778 <https://github.com/fmtlib/fmt/issues/1778>`_,
+  `#1781 <https://github.com/fmtlib/fmt/pull/1781>`_).
+  Thanks `@kammce (Khalil Estell) <https://github.com/kammce>`_.
+
+* Added the ``FMT_USE_INLINE_NAMESPACES`` macro to control usage of inline
+  namespaces (`#1945 <https://github.com/fmtlib/fmt/pull/1945>`_).
+  Thanks `@darklukee <https://github.com/darklukee>`_.
+
+* Improved build configuration
+  (`#1760 <https://github.com/fmtlib/fmt/pull/1760>`_,
+  `#1770 <https://github.com/fmtlib/fmt/pull/1770>`_,
+  `#1779 <https://github.com/fmtlib/fmt/issues/1779>`_,
+  `#1783 <https://github.com/fmtlib/fmt/pull/1783>`_,
+  `#1823 <https://github.com/fmtlib/fmt/pull/1823>`_).
+  Thanks `@dvetutnev (Dmitriy Vetutnev) <https://github.com/dvetutnev>`_,
+  `@xvitaly (Vitaly Zaitsev) <https://github.com/xvitaly>`_,
+  `@tambry (Raul Tambre) <https://github.com/tambry>`_,
+  `@medithe <https://github.com/medithe>`_,
+  `@martinwuehrer (Martin Wührer) <https://github.com/martinwuehrer>`_.
+
+* Fixed various warnings and compilation issues
+  (`#1790 <https://github.com/fmtlib/fmt/pull/1790>`_,
+  `#1802 <https://github.com/fmtlib/fmt/pull/1802>`_,
+  `#1808 <https://github.com/fmtlib/fmt/pull/1808>`_,
+  `#1810 <https://github.com/fmtlib/fmt/issues/1810>`_,
+  `#1811 <https://github.com/fmtlib/fmt/issues/1811>`_,
+  `#1812 <https://github.com/fmtlib/fmt/pull/1812>`_,
+  `#1814 <https://github.com/fmtlib/fmt/pull/1814>`_,
+  `#1816 <https://github.com/fmtlib/fmt/pull/1816>`_,
+  `#1817 <https://github.com/fmtlib/fmt/pull/1817>`_,
+  `#1818 <https://github.com/fmtlib/fmt/pull/1818>`_,
+  `#1825 <https://github.com/fmtlib/fmt/issues/1825>`_,
+  `#1836 <https://github.com/fmtlib/fmt/pull/1836>`_,
+  `#1855 <https://github.com/fmtlib/fmt/pull/1855>`_,
+  `#1856 <https://github.com/fmtlib/fmt/pull/1856>`_,
+  `#1860 <https://github.com/fmtlib/fmt/pull/1860>`_,
+  `#1877 <https://github.com/fmtlib/fmt/pull/1877>`_,
+  `#1879 <https://github.com/fmtlib/fmt/pull/1879>`_,
+  `#1880 <https://github.com/fmtlib/fmt/pull/1880>`_,
+  `#1896 <https://github.com/fmtlib/fmt/issues/1896>`_,
+  `#1897 <https://github.com/fmtlib/fmt/pull/1897>`_,
+  `#1898 <https://github.com/fmtlib/fmt/pull/1898>`_,
+  `#1904 <https://github.com/fmtlib/fmt/issues/1904>`_,
+  `#1908 <https://github.com/fmtlib/fmt/pull/1908>`_,
+  `#1911 <https://github.com/fmtlib/fmt/issues/1911>`_,
+  `#1912 <https://github.com/fmtlib/fmt/issues/1912>`_,
+  `#1928 <https://github.com/fmtlib/fmt/issues/1928>`_,
+  `#1929 <https://github.com/fmtlib/fmt/pull/1929>`_,
+  `#1935 <https://github.com/fmtlib/fmt/issues/1935>`_
+  `#1937 <https://github.com/fmtlib/fmt/pull/1937>`_,
+  `#1942 <https://github.com/fmtlib/fmt/pull/1942>`_,
+  `#1949 <https://github.com/fmtlib/fmt/issues/1949>`_).
+  Thanks `@TheQwertiest <https://github.com/TheQwertiest>`_,
+  `@medithe <https://github.com/medithe>`_,
+  `@martinwuehrer (Martin Wührer) <https://github.com/martinwuehrer>`_,
+  `@n16h7hunt3r <https://github.com/n16h7hunt3r>`_,
+  `@Othereum (Seokjin Lee) <https://github.com/Othereum>`_,
+  `@gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>`_,
+  `@AlexanderLanin (Alexander Lanin) <https://github.com/AlexanderLanin>`_,
+  `@gcerretani (Giovanni Cerretani) <https://github.com/gcerretani>`_,
+  `@chronoxor (Ivan Shynkarenka) <https://github.com/chronoxor>`_,
+  `@noizefloor (Jan Schwers) <https://github.com/noizefloor>`_,
+  `@akohlmey (Axel Kohlmeyer) <https://github.com/akohlmey>`_,
+  `@jk-jeon (Junekey Jeon) <https://github.com/jk-jeon>`_,
+  `@rimathia <https://github.com/rimathia>`_,
+  `@rglarix (Riccardo Ghetta (larix)) <https://github.com/rglarix>`_,
+  `@moiwi <https://github.com/moiwi>`_,
+  `@heckad (Kazantcev Andrey) <https://github.com/heckad>`_,
+  `@MarcDirven <https://github.com/MarcDirven>`_.
+  `@BartSiwek (Bart Siwek) <https://github.com/BartSiwek>`_,
+  `@darklukee <https://github.com/darklukee>`_.
+
+7.0.3 - 2020-08-06
+------------------
+
+* Worked around broken ``numeric_limits`` for 128-bit integers
+  (`#1787 <https://github.com/fmtlib/fmt/issues/1787>`_).
+
+* Added error reporting on missing named arguments
+  (`#1796 <https://github.com/fmtlib/fmt/issues/1796>`_).
+
+* Stopped using 128-bit integers with clang-cl
+  (`#1800 <https://github.com/fmtlib/fmt/pull/1800>`_).
+  Thanks `@Kingcom <https://github.com/Kingcom>`_.
+
+* Fixed issues in locale-specific integer formatting
+  (`#1782 <https://github.com/fmtlib/fmt/issues/1782>`_,
+  `#1801 <https://github.com/fmtlib/fmt/issues/1801>`_).
+
+7.0.2 - 2020-07-29
+------------------
+
+* Worked around broken ``numeric_limits`` for 128-bit integers
+  (`#1725 <https://github.com/fmtlib/fmt/issues/1725>`_).
+
+* Fixed compatibility with CMake 3.4
+  (`#1779 <https://github.com/fmtlib/fmt/issues/1779>`_).
+
+* Fixed handling of digit separators in locale-specific formatting
+  (`#1782 <https://github.com/fmtlib/fmt/issues/1782>`_).
+
+7.0.1 - 2020-07-07
+------------------
+
+* Updated the inline version namespace name.
+
+* Worked around a gcc bug in mangling of alias templates
+  (`#1753 <https://github.com/fmtlib/fmt/issues/1753>`_).
+
+* Fixed a linkage error on Windows
+  (`#1757 <https://github.com/fmtlib/fmt/issues/1757>`_).
+  Thanks `@Kurkin (Dmitry Kurkin) <https://github.com/Kurkin>`_.
+
+* Fixed minor issues with the documentation.
+
+7.0.0 - 2020-07-05
+------------------
+
+* Reduced the library size. For example, on macOS a stripped test binary
+  statically linked with {fmt} `shrank from ~368k to less than 100k
+  <http://www.zverovich.net/2020/05/21/reducing-library-size.html>`_.
+
+* Added a simpler and more efficient `format string compilation API
+  <https://fmt.dev/7.0.0/api.html#compile-api>`_:
+
+  .. code:: c++
+
+     #include <fmt/compile.h>
+
+     // Converts 42 into std::string using the most efficient method and no
+     // runtime format string processing.
+     std::string s = fmt::format(FMT_COMPILE("{}"), 42);
+
+  The old ``fmt::compile`` API is now deprecated.
+
+* Optimized integer formatting: ``format_to`` with format string compilation
+  and a stack-allocated buffer is now `faster than to_chars on both
+  libc++ and libstdc++
+  <http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_.
+
+* Optimized handling of small format strings. For example,
+
+  .. code:: c++
+
+      fmt::format("Result: {}: ({},{},{},{})", str1, str2, str3, str4, str5)
+
+  is now ~40% faster (`#1685 <https://github.com/fmtlib/fmt/issues/1685>`_).
+
+* Applied extern templates to improve compile times when using the core API
+  and ``fmt/format.h`` (`#1452 <https://github.com/fmtlib/fmt/issues/1452>`_).
+  For example, on macOS with clang the compile time of a test translation unit
+  dropped from 2.3s to 0.3s with ``-O2`` and from 0.6s to 0.3s with the default
+  settings (``-O0``).
+
+  Before (``-O2``)::
+
+    % time c++ -c test.cc -I include -std=c++17 -O2
+    c++ -c test.cc -I include -std=c++17 -O2  2.22s user 0.08s system 99% cpu 2.311 total
+
+  After (``-O2``)::
+
+    % time c++ -c test.cc -I include -std=c++17 -O2
+    c++ -c test.cc -I include -std=c++17 -O2  0.26s user 0.04s system 98% cpu 0.303 total
+
+  Before (default)::
+
+    % time c++ -c test.cc -I include -std=c++17
+    c++ -c test.cc -I include -std=c++17  0.53s user 0.06s system 98% cpu 0.601 total
+
+  After (default)::
+
+    % time c++ -c test.cc -I include -std=c++17
+    c++ -c test.cc -I include -std=c++17  0.24s user 0.06s system 98% cpu 0.301 total
+
+  It is still recommended to use ``fmt/core.h`` instead of ``fmt/format.h`` but
+  the compile time difference is now smaller. Thanks
+  `@alex3d <https://github.com/alex3d>`_ for the suggestion.
+
+* Named arguments are now stored on stack (no dynamic memory allocations) and
+  the compiled code is more compact and efficient. For example
+
+  .. code:: c++
+
+     #include <fmt/core.h>
+
+     int main() {
+       fmt::print("The answer is {answer}\n", fmt::arg("answer", 42));
+     }
+
+  compiles to just (`godbolt <https://godbolt.org/z/NcfEp_>`__)
+
+  .. code:: asm
+
+      .LC0:
+              .string "answer"
+      .LC1:
+              .string "The answer is {answer}\n"
+      main:
+              sub     rsp, 56
+              mov     edi, OFFSET FLAT:.LC1
+              mov     esi, 23
+              movabs  rdx, 4611686018427387905
+              lea     rax, [rsp+32]
+              lea     rcx, [rsp+16]
+              mov     QWORD PTR [rsp+8], 1
+              mov     QWORD PTR [rsp], rax
+              mov     DWORD PTR [rsp+16], 42
+              mov     QWORD PTR [rsp+32], OFFSET FLAT:.LC0
+              mov     DWORD PTR [rsp+40], 0
+              call    fmt::v6::vprint(fmt::v6::basic_string_view<char>,
+                                      fmt::v6::format_args)
+              xor     eax, eax
+              add     rsp, 56
+              ret
+
+          .L.str.1:
+                  .asciz  "answer"
+
+* Implemented compile-time checks for dynamic width and precision
+  (`#1614 <https://github.com/fmtlib/fmt/issues/1614>`_):
+
+  .. code:: c++
+
+     #include <fmt/format.h>
+
+     int main() {
+       fmt::print(FMT_STRING("{0:{1}}"), 42);
+     }
+
+  now gives a compilation error because argument 1 doesn't exist::
+
+    In file included from test.cc:1:
+    include/fmt/format.h:2726:27: error: constexpr variable 'invalid_format' must be
+    initialized by a constant expression
+      FMT_CONSTEXPR_DECL bool invalid_format =
+                              ^
+    ...
+    include/fmt/core.h:569:26: note: in call to
+    '&checker(s, {}).context_->on_error(&"argument not found"[0])'
+        if (id >= num_args_) on_error("argument not found");
+                            ^
+
+* Added sentinel support to ``fmt::join``
+  (`#1689 <https://github.com/fmtlib/fmt/pull/1689>`_)
+
+  .. code:: c++
+
+    struct zstring_sentinel {};
+    bool operator==(const char* p, zstring_sentinel) { return *p == '\0'; }
+    bool operator!=(const char* p, zstring_sentinel) { return *p != '\0'; }
+
+    struct zstring {
+      const char* p;
+      const char* begin() const { return p; }
+      zstring_sentinel end() const { return {}; }
+    };
+
+    auto s = fmt::format("{}", fmt::join(zstring{"hello"}, "_"));
+    // s == "h_e_l_l_o"
+
+  Thanks `@BRevzin (Barry Revzin) <https://github.com/BRevzin>`_.
+
+* Added support for named arguments, ``clear`` and ``reserve`` to
+  ``dynamic_format_arg_store``
+  (`#1655 <https://github.com/fmtlib/fmt/issues/1655>`_,
+  `#1663 <https://github.com/fmtlib/fmt/pull/1663>`_,
+  `#1674 <https://github.com/fmtlib/fmt/pull/1674>`_,
+  `#1677 <https://github.com/fmtlib/fmt/pull/1677>`_).
+  Thanks `@vsolontsov-ll (Vladimir Solontsov)
+  <https://github.com/vsolontsov-ll>`_.
+
+* Added support for the ``'c'`` format specifier to integral types for
+  compatibility with ``std::format``
+  (`#1652 <https://github.com/fmtlib/fmt/issues/1652>`_).
+
+* Replaced the ``'n'`` format specifier with ``'L'`` for compatibility with
+  ``std::format`` (`#1624 <https://github.com/fmtlib/fmt/issues/1624>`_).
+  The ``'n'`` specifier can be enabled via the ``FMT_DEPRECATED_N_SPECIFIER``
+  macro.
+
+* The ``'='`` format specifier is now disabled by default for compatibility with
+  ``std::format``. It can be enabled via the ``FMT_DEPRECATED_NUMERIC_ALIGN``
+  macro.
+
+* Removed the following deprecated APIs:
+
+  * ``FMT_STRING_ALIAS`` and ``fmt`` macros - replaced by ``FMT_STRING``
+  * ``fmt::basic_string_view::char_type`` - replaced by
+    ``fmt::basic_string_view::value_type``
+  * ``convert_to_int``
+  * ``format_arg_store::types``
+  * ``*parse_context`` - replaced by ``*format_parse_context``
+  * ``FMT_DEPRECATED_INCLUDE_OS``
+  * ``FMT_DEPRECATED_PERCENT`` - incompatible with ``std::format``
+  * ``*writer`` - replaced by compiled format API
+
+* Renamed the ``internal`` namespace to ``detail``
+  (`#1538 <https://github.com/fmtlib/fmt/issues/1538>`_). The former is still
+  provided as an alias if the ``FMT_USE_INTERNAL`` macro is defined.
+
+* Improved compatibility between ``fmt::printf`` with the standard specs
+  (`#1595 <https://github.com/fmtlib/fmt/issues/1595>`_,
+  `#1682 <https://github.com/fmtlib/fmt/pull/1682>`_,
+  `#1683 <https://github.com/fmtlib/fmt/pull/1683>`_,
+  `#1687 <https://github.com/fmtlib/fmt/pull/1687>`_,
+  `#1699 <https://github.com/fmtlib/fmt/pull/1699>`_).
+  Thanks `@rimathia <https://github.com/rimathia>`_.
+
+* Fixed handling of ``operator<<`` overloads that use ``copyfmt``
+  (`#1666 <https://github.com/fmtlib/fmt/issues/1666>`_).
+
+* Added the ``FMT_OS`` CMake option to control inclusion of OS-specific APIs
+  in the fmt target. This can be useful for embedded platforms
+  (`#1654 <https://github.com/fmtlib/fmt/issues/1654>`_,
+  `#1656 <https://github.com/fmtlib/fmt/pull/1656>`_).
+  Thanks `@kwesolowski (Krzysztof Wesolowski)
+  <https://github.com/kwesolowski>`_.
+
+* Replaced ``FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION`` with the ``FMT_FUZZ``
+  macro to prevent interferring with fuzzing of projects using {fmt}
+  (`#1650 <https://github.com/fmtlib/fmt/pull/1650>`_).
+  Thanks `@asraa (Asra Ali) <https://github.com/asraa>`_.
+
+* Fixed compatibility with emscripten
+  (`#1636 <https://github.com/fmtlib/fmt/issues/1636>`_,
+  `#1637 <https://github.com/fmtlib/fmt/pull/1637>`_).
+  Thanks `@ArthurSonzogni (Arthur Sonzogni)
+  <https://github.com/ArthurSonzogni>`_.
+
+* Improved documentation
+  (`#704 <https://github.com/fmtlib/fmt/issues/704>`_,
+  `#1643 <https://github.com/fmtlib/fmt/pull/1643>`_,
+  `#1660 <https://github.com/fmtlib/fmt/pull/1660>`_,
+  `#1681 <https://github.com/fmtlib/fmt/pull/1681>`_,
+  `#1691 <https://github.com/fmtlib/fmt/pull/1691>`_,
+  `#1706 <https://github.com/fmtlib/fmt/pull/1706>`_,
+  `#1714 <https://github.com/fmtlib/fmt/pull/1714>`_,
+  `#1721 <https://github.com/fmtlib/fmt/pull/1721>`_,
+  `#1739 <https://github.com/fmtlib/fmt/pull/1739>`_,
+  `#1740 <https://github.com/fmtlib/fmt/pull/1740>`_,
+  `#1741 <https://github.com/fmtlib/fmt/pull/1741>`_,
+  `#1751 <https://github.com/fmtlib/fmt/pull/1751>`_).
+  Thanks `@senior7515 (Alexander Gallego) <https://github.com/senior7515>`_,
+  `@lsr0 (Lindsay Roberts) <https://github.com/lsr0>`_,
+  `@puetzk (Kevin Puetz) <https://github.com/puetzk>`_,
+  `@fpelliccioni (Fernando Pelliccioni) <https://github.com/fpelliccioni>`_,
+  Alexey Kuzmenko, `@jelly (jelle van der Waa) <https://github.com/jelly>`_,
+  `@claremacrae (Clare Macrae) <https://github.com/claremacrae>`_,
+  `@jiapengwen (文佳鹏) <https://github.com/jiapengwen>`_,
+  `@gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>`_,
+  `@alexey-milovidov <https://github.com/alexey-milovidov>`_.
+
+* Implemented various build configuration fixes and improvements
+  (`#1603 <https://github.com/fmtlib/fmt/pull/1603>`_,
+  `#1657 <https://github.com/fmtlib/fmt/pull/1657>`_,
+  `#1702 <https://github.com/fmtlib/fmt/pull/1702>`_,
+  `#1728 <https://github.com/fmtlib/fmt/pull/1728>`_).
+  Thanks `@scramsby (Scott Ramsby) <https://github.com/scramsby>`_,
+  `@jtojnar (Jan Tojnar) <https://github.com/jtojnar>`_,
+  `@orivej (Orivej Desh) <https://github.com/orivej>`_,
+  `@flagarde <https://github.com/flagarde>`_.
+
+* Fixed various warnings and compilation issues
+  (`#1616 <https://github.com/fmtlib/fmt/pull/1616>`_,
+  `#1620 <https://github.com/fmtlib/fmt/issues/1620>`_,
+  `#1622 <https://github.com/fmtlib/fmt/issues/1622>`_,
+  `#1625 <https://github.com/fmtlib/fmt/issues/1625>`_,
+  `#1627 <https://github.com/fmtlib/fmt/pull/1627>`_,
+  `#1628 <https://github.com/fmtlib/fmt/issues/1628>`_,
+  `#1629 <https://github.com/fmtlib/fmt/pull/1629>`_,
+  `#1631 <https://github.com/fmtlib/fmt/issues/1631>`_,
+  `#1633 <https://github.com/fmtlib/fmt/pull/1633>`_,
+  `#1649 <https://github.com/fmtlib/fmt/pull/1649>`_,
+  `#1658 <https://github.com/fmtlib/fmt/issues/1658>`_,
+  `#1661 <https://github.com/fmtlib/fmt/pull/1661>`_,
+  `#1667 <https://github.com/fmtlib/fmt/pull/1667>`_,
+  `#1668 <https://github.com/fmtlib/fmt/issues/1668>`_,
+  `#1669 <https://github.com/fmtlib/fmt/pull/1669>`_,
+  `#1692 <https://github.com/fmtlib/fmt/issues/1692>`_,
+  `#1696 <https://github.com/fmtlib/fmt/pull/1696>`_,
+  `#1697 <https://github.com/fmtlib/fmt/pull/1697>`_,
+  `#1707 <https://github.com/fmtlib/fmt/issues/1707>`_,
+  `#1712 <https://github.com/fmtlib/fmt/pull/1712>`_,
+  `#1716 <https://github.com/fmtlib/fmt/pull/1716>`_,
+  `#1722 <https://github.com/fmtlib/fmt/pull/1722>`_,
+  `#1724 <https://github.com/fmtlib/fmt/issues/1724>`_,
+  `#1729 <https://github.com/fmtlib/fmt/pull/1729>`_,
+  `#1738 <https://github.com/fmtlib/fmt/pull/1738>`_,
+  `#1742 <https://github.com/fmtlib/fmt/issues/1742>`_,
+  `#1743 <https://github.com/fmtlib/fmt/issues/1743>`_,
+  `#1744 <https://github.com/fmtlib/fmt/pull/1744>`_,
+  `#1747 <https://github.com/fmtlib/fmt/issues/1747>`_,
+  `#1750 <https://github.com/fmtlib/fmt/pull/1750>`_).
+  Thanks `@gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>`_,
+  `@gabime (Gabi Melman) <https://github.com/gabime>`_,
+  `@johnor (Johan) <https://github.com/johnor>`_,
+  `@Kurkin (Dmitry Kurkin) <https://github.com/Kurkin>`_,
+  `@invexed (James Beach) <https://github.com/invexed>`_,
+  `@peterbell10 <https://github.com/peterbell10>`_,
+  `@daixtrose (Markus Werle) <https://github.com/daixtrose>`_,
+  `@petrutlucian94 (Lucian Petrut) <https://github.com/petrutlucian94>`_,
+  `@Neargye (Daniil Goncharov) <https://github.com/Neargye>`_,
+  `@ambitslix (Attila M. Szilagyi) <https://github.com/ambitslix>`_,
+  `@gabime (Gabi Melman) <https://github.com/gabime>`_,
+  `@erthink (Leonid Yuriev) <https://github.com/erthink>`_,
+  `@tohammer (Tobias Hammer) <https://github.com/tohammer>`_,
+  `@0x8000-0000 (Florin Iucha) <https://github.com/0x8000-0000>`_.
+
+6.2.1 - 2020-05-09
+------------------
+
+* Fixed ostream support in ``sprintf``
+  (`#1631 <https://github.com/fmtlib/fmt/issues/1631>`_).
+
+* Fixed type detection when using implicit conversion to ``string_view`` and
+  ostream ``operator<<`` inconsistently
+  (`#1662 <https://github.com/fmtlib/fmt/issues/1662>`_).
+
+6.2.0 - 2020-04-05
+------------------
+
+* Improved error reporting when trying to format an object of a non-formattable
+  type:
+
+  .. code:: c++
+
+     fmt::format("{}", S());
+
+  now gives::
+
+    include/fmt/core.h:1015:5: error: static_assert failed due to requirement
+    'formattable' "Cannot format argument. To make type T formattable provide a
+    formatter<T> specialization:
+    https://fmt.dev/latest/api.html#formatting-user-defined-types"
+        static_assert(
+        ^
+    ...
+    note: in instantiation of function template specialization
+    'fmt::v6::format<char [3], S, char>' requested here
+      fmt::format("{}", S());
+           ^
+
+  if ``S`` is not formattable.
+
+* Reduced the library size by ~10%.
+
+* Always print decimal point if ``#`` is specified
+  (`#1476 <https://github.com/fmtlib/fmt/issues/1476>`_,
+  `#1498 <https://github.com/fmtlib/fmt/issues/1498>`_):
+
+  .. code:: c++
+
+     fmt::print("{:#.0f}", 42.0);
+
+  now prints ``42.``
+
+* Implemented the ``'L'`` specifier for locale-specific numeric formatting to
+  improve compatibility with ``std::format``. The ``'n'`` specifier is now
+  deprecated and will be removed in the next major release.
+
+* Moved OS-specific APIs such as ``windows_error`` from ``fmt/format.h`` to
+  ``fmt/os.h``. You can define ``FMT_DEPRECATED_INCLUDE_OS`` to automatically
+  include ``fmt/os.h`` from ``fmt/format.h`` for compatibility but this will be
+  disabled in the next major release.
+
+* Added precision overflow detection in floating-point formatting.
+
+* Implemented detection of invalid use of ``fmt::arg``.
+
+* Used ``type_identity`` to block unnecessary template argument deduction.
+  Thanks Tim Song.
+
+* Improved UTF-8 handling
+  (`#1109 <https://github.com/fmtlib/fmt/issues/1109>`_):
+
+  .. code:: c++
+
+     fmt::print("┌{0:─^{2}}┐\n"
+                "│{1: ^{2}}│\n"
+                "└{0:─^{2}}┘\n", "", "Привет, мир!", 20);
+
+  now prints::
+
+     ┌────────────────────┐
+     │    Привет, мир!    │
+     └────────────────────┘
+
+  on systems that support Unicode.
+
+* Added experimental dynamic argument storage
+  (`#1170 <https://github.com/fmtlib/fmt/issues/1170>`_,
+  `#1584 <https://github.com/fmtlib/fmt/pull/1584>`_):
+
+  .. code:: c++
+
+     fmt::dynamic_format_arg_store<fmt::format_context> store;
+     store.push_back("answer");
+     store.push_back(42);
+     fmt::vprint("The {} is {}.\n", store);
+  
+  prints::
+
+     The answer is 42.
+
+  Thanks `@vsolontsov-ll (Vladimir Solontsov)
+  <https://github.com/vsolontsov-ll>`_.
+
+* Made ``fmt::join`` accept ``initializer_list``
+  (`#1591 <https://github.com/fmtlib/fmt/pull/1591>`_).
+  Thanks `@Rapotkinnik (Nikolay Rapotkin) <https://github.com/Rapotkinnik>`_.
+
+* Fixed handling of empty tuples
+  (`#1588 <https://github.com/fmtlib/fmt/issues/1588>`_).
+
+* Fixed handling of output iterators in ``format_to_n``
+  (`#1506 <https://github.com/fmtlib/fmt/issues/1506>`_).
+
+* Fixed formatting of ``std::chrono::duration`` types to wide output
+  (`#1533 <https://github.com/fmtlib/fmt/pull/1533>`_).
+  Thanks `@zeffy (pilao) <https://github.com/zeffy>`_.
+
+* Added const ``begin`` and ``end`` overload to buffers
+  (`#1553 <https://github.com/fmtlib/fmt/pull/1553>`_).
+  Thanks `@dominicpoeschko <https://github.com/dominicpoeschko>`_.
+
+* Added the ability to disable floating-point formatting via ``FMT_USE_FLOAT``,
+  ``FMT_USE_DOUBLE`` and ``FMT_USE_LONG_DOUBLE`` macros for extremely
+  memory-constrained embedded system
+  (`#1590 <https://github.com/fmtlib/fmt/pull/1590>`_).
+  Thanks `@albaguirre (Alberto Aguirre) <https://github.com/albaguirre>`_.
+
+* Made ``FMT_STRING`` work with ``constexpr`` ``string_view``
+  (`#1589 <https://github.com/fmtlib/fmt/pull/1589>`_).
+  Thanks `@scramsby (Scott Ramsby) <https://github.com/scramsby>`_.
+
+* Implemented a minor optimization in the format string parser
+  (`#1560 <https://github.com/fmtlib/fmt/pull/1560>`_).
+  Thanks `@IkarusDeveloper <https://github.com/IkarusDeveloper>`_.
+
+* Improved attribute detection
+  (`#1469 <https://github.com/fmtlib/fmt/pull/1469>`_,
+  `#1475 <https://github.com/fmtlib/fmt/pull/1475>`_,
+  `#1576 <https://github.com/fmtlib/fmt/pull/1576>`_).
+  Thanks `@federico-busato (Federico) <https://github.com/federico-busato>`_,
+  `@chronoxor (Ivan Shynkarenka) <https://github.com/chronoxor>`_,
+  `@refnum <https://github.com/refnum>`_.
+
+* Improved documentation
+  (`#1481 <https://github.com/fmtlib/fmt/pull/1481>`_,
+  `#1523 <https://github.com/fmtlib/fmt/pull/1523>`_).
+  Thanks `@JackBoosY (Jack·Boos·Yu) <https://github.com/JackBoosY>`_,
+  `@imba-tjd (谭九鼎) <https://github.com/imba-tjd>`_.
+
+* Fixed symbol visibility on Linux when compiling with ``-fvisibility=hidden``
+  (`#1535 <https://github.com/fmtlib/fmt/pull/1535>`_).
+  Thanks `@milianw (Milian Wolff) <https://github.com/milianw>`_.
+
+* Implemented various build configuration fixes and improvements
+  (`#1264 <https://github.com/fmtlib/fmt/issues/1264>`_,
+  `#1460 <https://github.com/fmtlib/fmt/issues/1460>`_,
+  `#1534 <https://github.com/fmtlib/fmt/pull/1534>`_,
+  `#1536 <https://github.com/fmtlib/fmt/issues/1536>`_,
+  `#1545 <https://github.com/fmtlib/fmt/issues/1545>`_,
+  `#1546 <https://github.com/fmtlib/fmt/pull/1546>`_,
+  `#1566 <https://github.com/fmtlib/fmt/issues/1566>`_,
+  `#1582 <https://github.com/fmtlib/fmt/pull/1582>`_,
+  `#1597 <https://github.com/fmtlib/fmt/issues/1597>`_,
+  `#1598 <https://github.com/fmtlib/fmt/pull/1598>`_).
+  Thanks `@ambitslix (Attila M. Szilagyi) <https://github.com/ambitslix>`_,
+  `@jwillikers (Jordan Williams) <https://github.com/jwillikers>`_,
+  `@stac47 (Laurent Stacul) <https://github.com/stac47>`_.
+
+* Fixed various warnings and compilation issues
+  (`#1433 <https://github.com/fmtlib/fmt/pull/1433>`_,
+  `#1461 <https://github.com/fmtlib/fmt/issues/1461>`_,
+  `#1470 <https://github.com/fmtlib/fmt/pull/1470>`_,
+  `#1480 <https://github.com/fmtlib/fmt/pull/1480>`_,
+  `#1485 <https://github.com/fmtlib/fmt/pull/1485>`_,
+  `#1492 <https://github.com/fmtlib/fmt/pull/1492>`_,
+  `#1493 <https://github.com/fmtlib/fmt/issues/1493>`_,
+  `#1504 <https://github.com/fmtlib/fmt/issues/1504>`_,
+  `#1505 <https://github.com/fmtlib/fmt/pull/1505>`_,
+  `#1512 <https://github.com/fmtlib/fmt/pull/1512>`_,
+  `#1515 <https://github.com/fmtlib/fmt/issues/1515>`_,
+  `#1516 <https://github.com/fmtlib/fmt/pull/1516>`_,
+  `#1518 <https://github.com/fmtlib/fmt/pull/1518>`_,
+  `#1519 <https://github.com/fmtlib/fmt/pull/1519>`_,
+  `#1520 <https://github.com/fmtlib/fmt/pull/1520>`_,
+  `#1521 <https://github.com/fmtlib/fmt/pull/1521>`_,
+  `#1522 <https://github.com/fmtlib/fmt/pull/1522>`_,
+  `#1524 <https://github.com/fmtlib/fmt/issues/1524>`_,
+  `#1530 <https://github.com/fmtlib/fmt/pull/1530>`_,
+  `#1531 <https://github.com/fmtlib/fmt/issues/1531>`_,
+  `#1532 <https://github.com/fmtlib/fmt/pull/1532>`_,
+  `#1539 <https://github.com/fmtlib/fmt/issues/1539>`_,
+  `#1547 <https://github.com/fmtlib/fmt/issues/1547>`_,
+  `#1548 <https://github.com/fmtlib/fmt/issues/1548>`_,
+  `#1554 <https://github.com/fmtlib/fmt/pull/1554>`_,
+  `#1567 <https://github.com/fmtlib/fmt/issues/1567>`_,
+  `#1568 <https://github.com/fmtlib/fmt/pull/1568>`_,
+  `#1569 <https://github.com/fmtlib/fmt/pull/1569>`_,
+  `#1571 <https://github.com/fmtlib/fmt/pull/1571>`_,
+  `#1573 <https://github.com/fmtlib/fmt/pull/1573>`_,
+  `#1575 <https://github.com/fmtlib/fmt/pull/1575>`_,
+  `#1581 <https://github.com/fmtlib/fmt/pull/1581>`_,
+  `#1583 <https://github.com/fmtlib/fmt/issues/1583>`_,
+  `#1586 <https://github.com/fmtlib/fmt/issues/1586>`_,
+  `#1587 <https://github.com/fmtlib/fmt/issues/1587>`_,
+  `#1594 <https://github.com/fmtlib/fmt/issues/1594>`_,
+  `#1596 <https://github.com/fmtlib/fmt/pull/1596>`_,
+  `#1604 <https://github.com/fmtlib/fmt/issues/1604>`_,
+  `#1606 <https://github.com/fmtlib/fmt/pull/1606>`_,
+  `#1607 <https://github.com/fmtlib/fmt/issues/1607>`_,
+  `#1609 <https://github.com/fmtlib/fmt/issues/1609>`_).
+  Thanks `@marti4d (Chris Martin) <https://github.com/marti4d>`_,
+  `@iPherian <https://github.com/iPherian>`_,
+  `@parkertomatoes <https://github.com/parkertomatoes>`_,
+  `@gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>`_,
+  `@chronoxor (Ivan Shynkarenka) <https://github.com/chronoxor>`_,
+  `@DanielaE (Daniela Engert) <https://github.com/DanielaE>`_,
+  `@torsten48 <https://github.com/torsten48>`_,
+  `@tohammer (Tobias Hammer) <https://github.com/tohammer>`_,
+  `@lefticus (Jason Turner) <https://github.com/lefticus>`_,
+  `@ryusakki (Haise) <https://github.com/ryusakki>`_,
+  `@adnsv (Alex Denisov) <https://github.com/adnsv>`_,
+  `@fghzxm <https://github.com/fghzxm>`_,
+  `@refnum <https://github.com/refnum>`_,
+  `@pramodk (Pramod Kumbhar) <https://github.com/pramodk>`_,
+  `@Spirrwell <https://github.com/Spirrwell>`_,
+  `@scramsby (Scott Ramsby) <https://github.com/scramsby>`_.
+
+6.1.2 - 2019-12-11
+------------------
+
+* Fixed ABI compatibility with ``libfmt.so.6.0.0``
+  (`#1471 <https://github.com/fmtlib/fmt/issues/1471>`_).
+
+* Fixed handling types convertible to ``std::string_view``
+  (`#1451 <https://github.com/fmtlib/fmt/pull/1451>`_).
+  Thanks `@denizevrenci (Deniz Evrenci) <https://github.com/denizevrenci>`_.
+
+* Made CUDA test an opt-in enabled via the ``FMT_CUDA_TEST`` CMake option.
+
+* Fixed sign conversion warnings
+  (`#1440 <https://github.com/fmtlib/fmt/pull/1440>`_).
+  Thanks `@0x8000-0000 (Florin Iucha) <https://github.com/0x8000-0000>`_.
+
 6.1.1 - 2019-12-04
 ------------------
 
@@ -358,16 +1358,16 @@
      #include <fmt/compile.h>
 
      auto f = fmt::compile<int>("{}");
-     std::string s = fmt::format(f, 42); // can be called multiple times to format
-                                         // different values
+     std::string s = fmt::format(f, 42); // can be called multiple times to
+                                         // format different values
      // s == "42"
 
   It moves the cost of parsing a format string outside of the format function
   which can be beneficial when identically formatting many objects of the same
   types. Thanks `@stryku (Mateusz Janek) <https://github.com/stryku>`_.
 
-* Added the ``%`` format specifier that formats floating-point values as
-  percentages (`#1060 <https://github.com/fmtlib/fmt/pull/1060>`_,
+* Added experimental ``%`` format specifier that formats floating-point values
+  as percentages (`#1060 <https://github.com/fmtlib/fmt/pull/1060>`_,
   `#1069 <https://github.com/fmtlib/fmt/pull/1069>`_,
   `#1071 <https://github.com/fmtlib/fmt/pull/1071>`_):
 
@@ -1130,7 +2130,7 @@
 
 * Implemented ``constexpr`` parsing of format strings and `compile-time format
   string checks
-  <https://fmt.dev/dev/api.html#compile-time-format-string-checks>`_. For
+  <https://fmt.dev/latest/api.html#compile-time-format-string-checks>`_. For
   example
 
   .. code:: c++
@@ -1191,7 +2191,7 @@
             throw format_error("invalid specifier");
 
 * Added `iterator support
-  <https://fmt.dev/dev/api.html#output-iterator-support>`_:
+  <https://fmt.dev/latest/api.html#output-iterator-support>`_:
 
   .. code:: c++
 
@@ -1202,7 +2202,7 @@
      fmt::format_to(std::back_inserter(out), "{}", 42);
 
 * Added the `format_to_n
-  <https://fmt.dev/dev/api.html#_CPPv2N3fmt11format_to_nE8OutputItNSt6size_tE11string_viewDpRK4Args>`_
+  <https://fmt.dev/latest/api.html#_CPPv2N3fmt11format_to_nE8OutputItNSt6size_tE11string_viewDpRK4Args>`_
   function that restricts the output to the specified number of characters
   (`#298 <https://github.com/fmtlib/fmt/issues/298>`_):
 
@@ -1213,7 +2213,7 @@
      // out == "1234" (without terminating '\0')
 
 * Added the `formatted_size
-  <https://fmt.dev/dev/api.html#_CPPv2N3fmt14formatted_sizeE11string_viewDpRK4Args>`_
+  <https://fmt.dev/latest/api.html#_CPPv2N3fmt14formatted_sizeE11string_viewDpRK4Args>`_
   function for computing the output size:
 
   .. code:: c++
@@ -1223,7 +2223,7 @@
      auto size = fmt::formatted_size("{}", 12345); // size == 5
 
 * Improved compile times by reducing dependencies on standard headers and
-  providing a lightweight `core API <https://fmt.dev/dev/api.html#core-api>`_:
+  providing a lightweight `core API <https://fmt.dev/latest/api.html#core-api>`_:
 
   .. code:: c++
 
@@ -1235,7 +2235,7 @@
   <https://github.com/fmtlib/fmt#compile-time-and-code-bloat>`_.
 
 * Added the `make_format_args
-  <https://fmt.dev/dev/api.html#_CPPv2N3fmt16make_format_argsEDpRK4Args>`_
+  <https://fmt.dev/latest/api.html#_CPPv2N3fmt16make_format_argsEDpRK4Args>`_
   function for capturing formatting arguments:
 
   .. code:: c++
@@ -1317,7 +2317,7 @@
      fmt::format("{} {two}", 1, fmt::arg("two", 2));
 
 * Removed the write API in favor of the `format API
-  <https://fmt.dev/dev/api.html#format-api>`_ with compile-time handling of
+  <https://fmt.dev/latest/api.html#format-api>`_ with compile-time handling of
   format strings.
 
 * Disallowed formatting of multibyte strings into a wide character target
diff --git a/METADATA b/METADATA
index 6ccb557..af55704 100644
--- a/METADATA
+++ b/METADATA
@@ -9,10 +9,11 @@
     type: GIT
     value: "https://github.com/fmtlib/fmt.git"
   }
-  version: "6.1.1"
+  version: "7.1.3"
+  license_type: NOTICE
   last_upgrade_date {
-    year: 2019
-    month: 12
-    day: 5
+    year: 2020
+    month: 11
+    day: 25
   }
 }
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..7529cb9
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/system/core:/janitors/OWNERS
diff --git a/README.rst b/README.rst
index 0d01227..acddc70 100644
--- a/README.rst
+++ b/README.rst
@@ -7,153 +7,174 @@
 .. image:: https://ci.appveyor.com/api/projects/status/ehjkiefde6gucy1v
    :target: https://ci.appveyor.com/project/vitaut/fmt
 
-.. image:: https://oss-fuzz-build-logs.storage.googleapis.com/badges/libfmt.svg
-   :alt: fmt is continuously fuzzed att oss-fuzz
-   :target: https://bugs.chromium.org/p/oss-fuzz/issues/list?colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20Summary&q=proj%3Dlibfmt&can=1
+.. image:: https://oss-fuzz-build-logs.storage.googleapis.com/badges/fmt.svg
+   :alt: fmt is continuously fuzzed at oss-fuzz
+   :target: https://bugs.chromium.org/p/oss-fuzz/issues/list?\
+            colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\
+            Summary&q=proj%3Dfmt&can=1
 
 .. image:: https://img.shields.io/badge/stackoverflow-fmt-blue.svg
    :alt: Ask questions at StackOverflow with the tag fmt
-   :target: http://stackoverflow.com/questions/tagged/fmt
+   :target: https://stackoverflow.com/questions/tagged/fmt
 
-**{fmt}** is an open-source formatting library for C++.
-It can be used as a safe and fast alternative to (s)printf and iostreams.
+**{fmt}** is an open-source formatting library providing a fast and safe
+alternative to C stdio and C++ iostreams.
 
-`Documentation <https://fmt.dev/latest/>`__
+If you like this project, please consider donating to BYSOL,
+an initiative to help victims of political repressions in Belarus:
+https://www.facebook.com/donate/759400044849707/108388587646909/.
 
-Q&A: ask questions on `StackOverflow with the tag fmt <http://stackoverflow.com/questions/tagged/fmt>`_.
+`Documentation <https://fmt.dev>`__
+
+Q&A: ask questions on `StackOverflow with the tag fmt
+<https://stackoverflow.com/questions/tagged/fmt>`_.
+
+Try {fmt} in `Compiler Explorer <https://godbolt.org/z/Eq5763>`_.
 
 Features
 --------
 
-* Replacement-based `format API <https://fmt.dev/dev/api.html>`_ with
-  positional arguments for localization.
-* `Format string syntax <https://fmt.dev/dev/syntax.html>`_ similar to the one
-  of `str.format <https://docs.python.org/3/library/stdtypes.html#str.format>`_
-  in Python.
+* Simple `format API <https://fmt.dev/latest/api.html>`_ with positional arguments
+  for localization
+* Implementation of `C++20 std::format
+  <https://en.cppreference.com/w/cpp/utility/format>`__
+* `Format string syntax <https://fmt.dev/latest/syntax.html>`_ similar to Python's
+  `format <https://docs.python.org/3/library/stdtypes.html#str.format>`_
+* Fast IEEE 754 floating-point formatter with correct rounding, shortness and
+  round-trip guarantees
 * Safe `printf implementation
-  <https://fmt.dev/latest/api.html#printf-formatting>`_ including
-  the POSIX extension for positional arguments.
-* Implementation of `C++20 std::format <https://fmt.dev/Text%20Formatting.html>`__.
-* Support for user-defined types.
+  <https://fmt.dev/latest/api.html#printf-formatting>`_ including the POSIX
+  extension for positional arguments
+* Extensibility: `support for user-defined types
+  <https://fmt.dev/latest/api.html#formatting-user-defined-types>`_
 * High performance: faster than common standard library implementations of
-  `printf <http://en.cppreference.com/w/cpp/io/c/fprintf>`_ and
-  iostreams. See `Speed tests`_ and `Fast integer to string conversion in C++
-  <http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_.
-* Small code size both in terms of source code (the minimum configuration
-  consists of just three header files, ``core.h``, ``format.h`` and
-  ``format-inl.h``) and compiled code. See `Compile time and code bloat`_.
-* Reliability: the library has an extensive set of `unit tests
-  <https://github.com/fmtlib/fmt/tree/master/test>`_ and is continuously fuzzed.
+  ``(s)printf``, iostreams, ``to_string`` and ``to_chars``, see `Speed tests`_
+  and `Converting a hundred million integers to strings per second
+  <http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_
+* Small code size both in terms of source code with the minimum configuration
+  consisting of just three files, ``core.h``, ``format.h`` and ``format-inl.h``,
+  and compiled code; see `Compile time and code bloat`_
+* Reliability: the library has an extensive set of `tests
+  <https://github.com/fmtlib/fmt/tree/master/test>`_ and is `continuously fuzzed
+  <https://bugs.chromium.org/p/oss-fuzz/issues/list?colspec=ID%20Type%20
+  Component%20Status%20Proj%20Reported%20Owner%20Summary&q=proj%3Dfmt&can=1>`_
 * Safety: the library is fully type safe, errors in format strings can be
   reported at compile time, automatic memory management prevents buffer overflow
-  errors.
+  errors
 * Ease of use: small self-contained code base, no external dependencies,
   permissive MIT `license
   <https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_
 * `Portability <https://fmt.dev/latest/index.html#portability>`_ with
-  consistent output across platforms and support for older compilers.
-* Clean warning-free codebase even on high warning levels
-  (``-Wall -Wextra -pedantic``).
-* Support for wide strings.
-* Optional header-only configuration enabled with the ``FMT_HEADER_ONLY`` macro.
+  consistent output across platforms and support for older compilers
+* Clean warning-free codebase even on high warning levels such as
+  ``-Wall -Wextra -pedantic``
+* Locale-independence by default
+* Optional header-only configuration enabled with the ``FMT_HEADER_ONLY`` macro
 
-See the `documentation <https://fmt.dev/latest/>`_ for more details.
+See the `documentation <https://fmt.dev>`_ for more details.
 
 Examples
 --------
 
-Print ``Hello, world!`` to ``stdout``:
+**Print to stdout** (`run <https://godbolt.org/z/Tevcjh>`_)
 
 .. code:: c++
 
-    fmt::print("Hello, {}!", "world");  // Python-like format string syntax
-    fmt::printf("Hello, %s!", "world"); // printf format string syntax
+    #include <fmt/core.h>
+    
+    int main() {
+      fmt::print("Hello, world!\n");
+    }
 
-Format a string and use positional arguments:
+**Format a string** (`run <https://godbolt.org/z/oK8h33>`_)
+
+.. code:: c++
+
+    std::string s = fmt::format("The answer is {}.", 42);
+    // s == "The answer is 42."
+
+**Format a string using positional arguments** (`run <https://godbolt.org/z/Yn7Txe>`_)
 
 .. code:: c++
 
     std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy");
     // s == "I'd rather be happy than right."
 
-Check a format string at compile time:
+**Print chrono durations** (`run <https://godbolt.org/z/K8s4Mc>`_)
 
 .. code:: c++
 
-    // test.cc
-    #include <fmt/format.h>
-    std::string s = format(FMT_STRING("{2}"), 42);
+    #include <fmt/chrono.h>
 
-.. code::
-
-    $ c++ -Iinclude -std=c++14 test.cc
-    ...
-    test.cc:4:17: note: in instantiation of function template specialization 'fmt::v5::format<S, int>' requested here
-    std::string s = format(FMT_STRING("{2}"), 42);
-                    ^
-    include/fmt/core.h:778:19: note: non-constexpr function 'on_error' cannot be used in a constant expression
-        ErrorHandler::on_error(message);
-                      ^
-    include/fmt/format.h:2226:16: note: in call to '&checker.context_->on_error(&"argument index out of range"[0])'
-          context_.on_error("argument index out of range");
-                   ^
-
-Use {fmt} as a safe portable replacement for ``itoa``
-(`godbolt <https://godbolt.org/g/NXmpU4>`_):
-
-.. code:: c++
-
-    fmt::memory_buffer buf;
-    format_to(buf, "{}", 42);    // replaces itoa(42, buffer, 10)
-    format_to(buf, "{:x}", 42);  // replaces itoa(42, buffer, 16)
-    // access the string with to_string(buf) or buf.data()
-
-Format objects of user-defined types via a simple `extension API
-<https://fmt.dev/latest/api.html#formatting-user-defined-types>`_:
-
-.. code:: c++
-
-    #include "fmt/format.h"
-
-    struct date {
-      int year, month, day;
-    };
-
-    template <>
-    struct fmt::formatter<date> {
-      constexpr auto parse(format_parse_context& ctx) { return ctx.begin(); }
-
-      template <typename FormatContext>
-      auto format(const date& d, FormatContext& ctx) {
-        return format_to(ctx.out(), "{}-{}-{}", d.year, d.month, d.day);
-      }
-    };
-
-    std::string s = fmt::format("The date is {}", date{2012, 12, 9});
-    // s == "The date is 2012-12-9"
-
-Create your own functions similar to `format
-<https://fmt.dev/latest/api.html#format>`_ and
-`print <https://fmt.dev/latest/api.html#print>`_
-which take arbitrary arguments (`godbolt <https://godbolt.org/g/MHjHVf>`_):
-
-.. code:: c++
-
-    // Prints formatted error message.
-    void vreport_error(const char* format, fmt::format_args args) {
-      fmt::print("Error: ");
-      fmt::vprint(format, args);
-    }
-    template <typename... Args>
-    void report_error(const char* format, const Args & ... args) {
-      vreport_error(format, fmt::make_format_args(args...));
+    int main() {
+      using namespace std::literals::chrono_literals;
+      fmt::print("Default format: {} {}\n", 42s, 100ms);
+      fmt::print("strftime-like format: {:%H:%M:%S}\n", 3h + 15min + 30s);
     }
 
-    report_error("file not found: {}", path);
+Output::
 
-Note that ``vreport_error`` is not parameterized on argument types which can
-improve compile times and reduce code size compared to a fully parameterized
-version.
+    Default format: 42s 100ms
+    strftime-like format: 03:15:30
+
+**Print a container** (`run <https://godbolt.org/z/MjsY7c>`_)
+
+.. code:: c++
+
+    #include <vector>
+    #include <fmt/ranges.h>
+
+    int main() {
+      std::vector<int> v = {1, 2, 3};
+      fmt::print("{}\n", v);
+    }
+
+Output::
+
+    {1, 2, 3}
+
+**Check a format string at compile time**
+
+.. code:: c++
+
+    std::string s = fmt::format(FMT_STRING("{:d}"), "don't panic");
+
+This gives a compile-time error because ``d`` is an invalid format specifier for
+a string.
+
+**Write a file from a single thread**
+
+.. code:: c++
+
+    #include <fmt/os.h>
+
+    int main() {
+      auto out = fmt::output_file("guide.txt");
+      out.print("Don't {}", "Panic");
+    }
+
+This can be `5 to 9 times faster than fprintf
+<http://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html>`_.
+
+**Print with colors and text styles**
+
+.. code:: c++
+
+    #include <fmt/color.h>
+
+    int main() {
+      fmt::print(fg(fmt::color::crimson) | fmt::emphasis::bold,
+                 "Hello, {}!\n", "world");
+      fmt::print(fg(fmt::color::floral_white) | bg(fmt::color::slate_gray) |
+                 fmt::emphasis::underline, "Hello, {}!\n", "мир");
+      fmt::print(fg(fmt::color::steel_blue) | fmt::emphasis::italic,
+                 "Hello, {}!\n", "世界");
+    }
+
+Output on a modern terminal:
+
+.. image:: https://user-images.githubusercontent.com/
+           576385/88485597-d312f600-cf2b-11ea-9cbe-61f535a86e28.png
 
 Benchmarks
 ----------
@@ -164,9 +185,9 @@
 ================= ============= ===========
 Library           Method        Run Time, s
 ================= ============= ===========
-libc              printf          1.03
-libc++            std::ostream    2.98
-{fmt} 4de41a      fmt::print      0.76
+libc              printf          1.04
+libc++            std::ostream    3.05
+{fmt} 6.1.1       fmt::print      0.75
 Boost Format 1.67 boost::format   7.24
 Folly Format      folly::format   2.23
 ================= ============= ===========
@@ -174,18 +195,20 @@
 {fmt} is the fastest of the benchmarked methods, ~35% faster than ``printf``.
 
 The above results were generated by building ``tinyformat_test.cpp`` on macOS
-10.14.3 with ``clang++ -O3 -DSPEED_TEST -DHAVE_FORMAT``, and taking the best of
-three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
+10.14.6 with ``clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT``, and taking the
+best of three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
 or equivalent is filled 2,000,000 times with output sent to ``/dev/null``; for
 further details refer to the `source
 <https://github.com/fmtlib/format-benchmark/blob/master/tinyformat_test.cpp>`_.
 
-{fmt} is 10x faster than ``std::ostringstream`` and ``sprintf`` on floating-point
-formatting (`dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>`_)
-and as fast as `double-conversion <https://github.com/google/double-conversion>`_:
+{fmt} is up to 20-30x faster than ``std::ostringstream`` and ``sprintf`` on
+floating-point formatting (`dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>`_)
+and faster than `double-conversion <https://github.com/google/double-conversion>`_ and
+`ryu <https://github.com/ulfjack/ryu>`_:
 
-.. image:: https://user-images.githubusercontent.com/576385/69767160-cdaca400-112f-11ea-9fc5-347c9f83caad.png
-   :target: https://fmt.dev/unknown_mac64_clang10.0.html
+.. image:: https://user-images.githubusercontent.com/576385/
+           95684665-11719600-0ba8-11eb-8e5b-972ff4e49428.png
+   :target: https://fmt.dev/unknown_mac64_clang12.0.html
 
 Compile time and code bloat
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -264,36 +287,33 @@
 Projects using this library
 ---------------------------
 
-* `0 A.D. <http://play0ad.com/>`_: A free, open-source, cross-platform real-time
-  strategy game
+* `0 A.D. <https://play0ad.com/>`_: a free, open-source, cross-platform
+  real-time strategy game
 
 * `AMPL/MP <https://github.com/ampl/mp>`_:
-  An open-source library for mathematical programming
-  
-* `AvioBook <https://www.aviobook.aero/en>`_: A comprehensive aircraft
+  an open-source library for mathematical programming
+
+* `Aseprite <https://github.com/aseprite/aseprite>`_:
+  animated sprite editor & pixel art tool 
+
+* `AvioBook <https://www.aviobook.aero/en>`_: a comprehensive aircraft
   operations suite
   
-* `Celestia <https://celestia.space/>`_: Real-time 3D visualization of space
+* `Blizzard Battle.net <https://battle.net/>`_: an online gaming platform
+  
+* `Celestia <https://celestia.space/>`_: real-time 3D visualization of space
 
-* `Ceph <https://ceph.com/>`_: A scalable distributed storage system
+* `Ceph <https://ceph.com/>`_: a scalable distributed storage system
 
-* `ccache <https://ccache.dev/>`_: A compiler cache
+* `ccache <https://ccache.dev/>`_: a compiler cache
+
+* `ClickHouse <https://github.com/ClickHouse/ClickHouse>`_: analytical database
+  management system
 
 * `CUAUV <http://cuauv.org/>`_: Cornell University's autonomous underwater
   vehicle
 
-* `HarpyWar/pvpgn <https://github.com/pvpgn/pvpgn-server>`_:
-  Player vs Player Gaming Network with tweaks
-
-* `KBEngine <http://kbengine.org/>`_: An open-source MMOG server engine
-
-* `Keypirinha <http://keypirinha.com/>`_: A semantic launcher for Windows
-
-* `Kodi <https://kodi.tv/>`_ (formerly xbmc): Home theater software
-
-* `Lifeline <https://github.com/peter-clark/lifeline>`_: A 2D game
-
-* `Drake <http://drake.mit.edu/>`_: A planning, control, and analysis toolbox
+* `Drake <https://drake.mit.edu/>`_: a planning, control, and analysis toolbox
   for nonlinear dynamical systems (MIT)
 
 * `Envoy <https://lyft.github.io/envoy/>`_: C++ L7 proxy and communication bus
@@ -301,49 +321,76 @@
 
 * `FiveM <https://fivem.net/>`_: a modification framework for GTA V
 
-* `MongoDB <https://mongodb.com/>`_: Distributed document database
+* `Folly <https://github.com/facebook/folly>`_: Facebook open-source library
 
-* `MongoDB Smasher <https://github.com/duckie/mongo_smasher>`_: A small tool to
+* `HarpyWar/pvpgn <https://github.com/pvpgn/pvpgn-server>`_:
+  Player vs Player Gaming Network with tweaks
+
+* `KBEngine <https://github.com/kbengine/kbengine>`_: an open-source MMOG server
+  engine
+
+* `Keypirinha <https://keypirinha.com/>`_: a semantic launcher for Windows
+
+* `Kodi <https://kodi.tv/>`_ (formerly xbmc): home theater software
+
+* `Knuth <https://kth.cash/>`_: high-performance Bitcoin full-node
+
+* `Microsoft Verona <https://github.com/microsoft/verona>`_:
+  research programming language for concurrent ownership
+
+* `MongoDB <https://mongodb.com/>`_: distributed document database
+
+* `MongoDB Smasher <https://github.com/duckie/mongo_smasher>`_: a small tool to
   generate randomized datasets
 
-* `OpenSpace <http://openspaceproject.com/>`_: An open-source astrovisualization
-  framework
+* `OpenSpace <https://openspaceproject.com/>`_: an open-source
+  astrovisualization framework
 
-* `PenUltima Online (POL) <http://www.polserver.com/>`_:
-  An MMO server, compatible with most Ultima Online clients
+* `PenUltima Online (POL) <https://www.polserver.com/>`_:
+  an MMO server, compatible with most Ultima Online clients
 
-* `quasardb <https://www.quasardb.net/>`_: A distributed, high-performance,
+* `PyTorch <https://github.com/pytorch/pytorch>`_: an open-source machine
+  learning library
+
+* `quasardb <https://www.quasardb.net/>`_: a distributed, high-performance,
   associative database
+  
+* `Quill <https://github.com/odygrd/quill>`_: asynchronous low-latency logging library
 
-* `readpe <https://bitbucket.org/sys_dev/readpe>`_: Read Portable Executable
+* `QKW <https://github.com/ravijanjam/qkw>`_: generalizing aliasing to simplify
+  navigation, and executing complex multi-line terminal command sequences
 
-* `redis-cerberus <https://github.com/HunanTV/redis-cerberus>`_: A Redis cluster
+* `redis-cerberus <https://github.com/HunanTV/redis-cerberus>`_: a Redis cluster
   proxy
 
-* `rpclib <http://rpclib.net/>`_: A modern C++ msgpack-RPC server and client
+* `redpanda <https://vectorized.io/redpanda>`_: a 10x faster Kafka® replacement
+  for mission critical systems written in C++
+
+* `rpclib <http://rpclib.net/>`_: a modern C++ msgpack-RPC server and client
   library
 
-* `Saddy <https://github.com/mamontov-cpp/saddy-graphics-engine-2d>`_:
-  Small crossplatform 2D graphic engine
+* `Salesforce Analytics Cloud
+  <https://www.salesforce.com/analytics-cloud/overview/>`_:
+  business intelligence software
 
-* `Salesforce Analytics Cloud <http://www.salesforce.com/analytics-cloud/overview/>`_:
-  Business intelligence software
-
-* `Scylla <http://www.scylladb.com/>`_: A Cassandra-compatible NoSQL data store
+* `Scylla <https://www.scylladb.com/>`_: a Cassandra-compatible NoSQL data store
   that can handle 1 million transactions per second on a single server
 
-* `Seastar <http://www.seastar-project.org/>`_: An advanced, open-source C++
+* `Seastar <http://www.seastar-project.org/>`_: an advanced, open-source C++
   framework for high-performance server applications on modern hardware
 
-* `spdlog <https://github.com/gabime/spdlog>`_: Super fast C++ logging library
+* `spdlog <https://github.com/gabime/spdlog>`_: super fast C++ logging library
 
-* `Stellar <https://www.stellar.org/>`_: Financial platform
+* `Stellar <https://www.stellar.org/>`_: financial platform
 
-* `Touch Surgery <https://www.touchsurgery.com/>`_: Surgery simulator
+* `Touch Surgery <https://www.touchsurgery.com/>`_: surgery simulator
 
-* `TrinityCore <https://github.com/TrinityCore/TrinityCore>`_: Open-source
+* `TrinityCore <https://github.com/TrinityCore/TrinityCore>`_: open-source
   MMORPG framework
 
+* `Windows Terminal <https://github.com/microsoft/terminal>`_: the new Windows
+  terminal
+
 `More... <https://github.com/search?q=fmtlib&type=Code>`_
 
 If you are aware of other projects using this library, please let me know
@@ -368,7 +415,7 @@
 being a part of the C standard library. The main drawback is that it
 doesn't support user-defined types. ``printf`` also has safety issues although
 they are somewhat mitigated with `__attribute__ ((format (printf, ...))
-<http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html>`_ in GCC.
+<https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html>`_ in GCC.
 There is a POSIX extension that adds positional arguments required for
 `i18n <https://en.wikipedia.org/wiki/Internationalization_and_localization>`_
 to ``printf`` but it is not a part of C99 and may not be available on some
@@ -400,15 +447,15 @@
 
 This is a very powerful library which supports both ``printf``-like format
 strings and positional arguments. Its main drawback is performance. According to
-various benchmarks it is much slower than other methods considered here. Boost
+various, benchmarks it is much slower than other methods considered here. Boost
 Format also has excessive build times and severe code bloat issues (see
 `Benchmarks`_).
 
 FastFormat
 ~~~~~~~~~~
 
-This is an interesting library which is fast, safe and has positional
-arguments. However it has significant limitations, citing its author:
+This is an interesting library which is fast, safe and has positional arguments.
+However, it has significant limitations, citing its author:
 
     Three features that have no hope of being accommodated within the
     current design are:
@@ -417,8 +464,8 @@
     * Octal/hexadecimal encoding
     * Runtime width/alignment specification
 
-It is also quite big and has a heavy dependency, STLSoft, which might be
-too restrictive for using it in some projects.
+It is also quite big and has a heavy dependency, STLSoft, which might be too
+restrictive for using it in some projects.
 
 Boost Spirit.Karma
 ~~~~~~~~~~~~~~~~~~
@@ -426,32 +473,9 @@
 This is not really a formatting library but I decided to include it here for
 completeness. As iostreams, it suffers from the problem of mixing verbatim text
 with arguments. The library is pretty fast, but slower on integer formatting
-than ``fmt::format_int`` on Karma's own benchmark,
-see `Fast integer to string conversion in C++
-<http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_.
-
-FAQ
----
-
-Q: how can I capture formatting arguments and format them later?
-
-A: use ``std::tuple``:
-
-.. code:: c++
-
-   template <typename... Args>
-   auto capture(const Args&... args) {
-     return std::make_tuple(args...);
-   }
-
-   auto print_message = [](const auto&... args) {
-     fmt::print(args...);
-   };
-
-   // Capture and store arguments:
-   auto args = capture("{} {}", 42, "foo");
-   // Do formatting:
-   std::apply(print_message, args);
+than ``fmt::format_to`` with format string compilation on Karma's own benchmark,
+see `Converting a hundred million integers to strings per second
+<http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_.
 
 License
 -------
@@ -459,18 +483,19 @@
 {fmt} is distributed under the MIT `license
 <https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_.
 
-The `Format String Syntax
-<https://fmt.dev/latest/syntax.html>`_
-section in the documentation is based on the one from Python `string module
-documentation <https://docs.python.org/3/library/string.html#module-string>`_
-adapted for the current library. For this reason the documentation is
-distributed under the Python Software Foundation license available in
-`doc/python-license.txt
-<https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt>`_.
-It only applies if you distribute the documentation of fmt.
+Documentation License
+---------------------
 
-Acknowledgments
----------------
+The `Format String Syntax <https://fmt.dev/latest/syntax.html>`_
+section in the documentation is based on the one from Python `string module
+documentation <https://docs.python.org/3/library/string.html#module-string>`_.
+For this reason the documentation is distributed under the Python Software
+Foundation license available in `doc/python-license.txt
+<https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt>`_.
+It only applies if you distribute the documentation of {fmt}.
+
+Maintainers
+-----------
 
 The {fmt} library is maintained by Victor Zverovich (`vitaut
 <https://github.com/vitaut>`_) and Jonathan Müller (`foonathan
@@ -479,23 +504,3 @@
 `Releases <https://github.com/fmtlib/fmt/releases>`_ for some of the names.
 Let us know if your contribution is not listed or mentioned incorrectly and
 we'll make it right.
-
-The benchmark section of this readme file and the performance tests are taken
-from the excellent `tinyformat <https://github.com/c42f/tinyformat>`_ library
-written by Chris Foster.  Boost Format library is acknowledged transitively
-since it had some influence on tinyformat.
-Some ideas used in the implementation are borrowed from `Loki
-<http://loki-lib.sourceforge.net/>`_ SafeFormat and `Diagnostic API
-<http://clang.llvm.org/doxygen/classclang_1_1Diagnostic.html>`_ in
-`Clang <http://clang.llvm.org/>`_.
-Format string syntax and the documentation are based on Python's `str.format
-<https://docs.python.org/3/library/stdtypes.html#str.format>`_.
-Thanks `Doug Turnbull <https://github.com/softwaredoug>`_ for his valuable
-comments and contribution to the design of the type-safe API and
-`Gregory Czajkowski <https://github.com/gcflymoto>`_ for implementing binary
-formatting. Thanks `Ruslan Baratov <https://github.com/ruslo>`_ for comprehensive
-`comparison of integer formatting algorithms <https://github.com/ruslo/int-dec-format-tests>`_
-and useful comments regarding performance, `Boris Kaul <https://github.com/localvoid>`_ for
-`C++ counting digits benchmark <https://github.com/localvoid/cxx-benchmark-count-digits>`_.
-Thanks to `CarterLi <https://github.com/CarterLi>`_ for contributing various
-improvements to the code.
diff --git a/TEST_MAPPING b/TEST_MAPPING
new file mode 100644
index 0000000..caeecd6
--- /dev/null
+++ b/TEST_MAPPING
@@ -0,0 +1,10 @@
+{
+  "presubmit": [
+    {
+      "name": "fmtlib_test"
+    },
+    {
+      "name": "fmtlib_ostream_test"
+    }
+  ]
+}
diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index f3dae60..0684845 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -4,9 +4,14 @@
   return ()
 endif ()
 
+find_package(PythonInterp QUIET REQUIRED)
+
 add_custom_target(doc
-  COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/build.py ${FMT_VERSION}
+  COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/build.py
+                               ${FMT_VERSION}
   SOURCES api.rst syntax.rst usage.rst build.py conf.py _templates/layout.html)
 
+include(GNUInstallDirs)
 install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html/
-        DESTINATION share/doc/fmt OPTIONAL)
+        DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/doc/fmt OPTIONAL
+        PATTERN ".doctrees" EXCLUDE)
diff --git a/doc/_templates/layout.html b/doc/_templates/layout.html
index d5f4b70..333a606 100644
--- a/doc/_templates/layout.html
+++ b/doc/_templates/layout.html
@@ -6,14 +6,13 @@
 <meta name="author" content="Victor Zverovich">
 <link rel="stylesheet" href="_static/fmt.css">
 {# Google Analytics #}
+<script async src="https://www.googletagmanager.com/gtag/js?id=UA-20116650-4"></script>
 <script>
-  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-    (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();
-    a=s.createElement(o),m=s.getElementsByTagName(o)[0];a.async=1;
-    a.src=g;m.parentNode.insertBefore(a,m)
-  })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
-  ga('create', 'UA-20116650-4', 'fmtlib.net');
-  ga('send', 'pageview');
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
+
+  gtag('config', 'UA-20116650-4');
 </script>
 {% endblock %}
 
diff --git a/doc/api.rst b/doc/api.rst
index 0834a87..9b6c0f3 100644
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -9,10 +9,13 @@
 * :ref:`fmt/core.h <core-api>`: the core API providing argument handling
   facilities and a lightweight subset of formatting functions
 * :ref:`fmt/format.h <format-api>`: the full format API providing compile-time
-  format string checks, output iterator and user-defined type support
+  format string checks, wide string, output iterator and user-defined type
+  support
 * :ref:`fmt/ranges.h <ranges-api>`: additional formatting support for ranges
   and tuples
 * :ref:`fmt/chrono.h <chrono-api>`: date and time formatting
+* :ref:`fmt/compile.h <compile-api>`: format string compilation
+* :ref:`fmt/color.h <color-api>`: terminal color and text style
 * :ref:`fmt/ostream.h <ostream-api>`: ``std::ostream`` support
 * :ref:`fmt/printf.h <printf-api>`: ``printf`` formatting
 
@@ -43,7 +46,11 @@
 .. _format:
 
 .. doxygenfunction:: format(const S&, Args&&...)
-.. doxygenfunction:: vformat(const S&, basic_format_args<buffer_context<Char>>)
+.. doxygenfunction:: vformat(const S&, basic_format_args<buffer_context<type_identity_t<Char>>>)
+
+.. doxygenfunction:: fmt::format_to(OutputIt, const S&, Args&&...)
+.. doxygenfunction:: fmt::format_to_n(OutputIt, size_t, const S&, const Args&...)
+.. doxygenfunction:: fmt::formatted_size(string_view, Args&&...)
 
 .. _print:
 
@@ -63,11 +70,43 @@
 Argument Lists
 --------------
 
+You can create your own formatting function with compile-time checks and small
+binary footprint, for example (https://godbolt.org/z/oba4Mc):
+
+.. code:: c++
+
+    #include <fmt/format.h>
+
+    void vlog(const char* file, int line, fmt::string_view format,
+              fmt::format_args args) {
+      fmt::print("{}: {}: ", file, line);
+      fmt::vprint(format, args);
+    }
+
+    template <typename S, typename... Args>
+    void log(const char* file, int line, const S& format, Args&&... args) {
+      vlog(file, line, format,
+          fmt::make_args_checked<Args...>(format, args...));
+    }
+
+    #define MY_LOG(format, ...) \
+      log(__FILE__, __LINE__, FMT_STRING(format), __VA_ARGS__)
+
+    MY_LOG("invalid squishiness: {}", 42);
+
+Note that ``vlog`` is not parameterized on argument types which improves compile
+times and reduces binary code size compared to a fully parameterized version.
+
+.. doxygenfunction:: fmt::make_args_checked(const S&, const remove_reference_t<Args>&...)
+
 .. doxygenfunction:: fmt::make_format_args(const Args&...)
 
 .. doxygenclass:: fmt::format_arg_store
    :members:
 
+.. doxygenclass:: fmt::dynamic_format_arg_store
+   :members:
+
 .. doxygenclass:: fmt::basic_format_args
    :members:
 
@@ -85,23 +124,38 @@
 .. doxygentypedef:: fmt::string_view
 .. doxygentypedef:: fmt::wstring_view
 
+Locale
+------
+
+All formatting is locale-independent by default. Use the ``'L'`` format
+specifier to insert the appropriate number separator characters from the
+locale::
+
+  #include <fmt/core.h>
+  #include <locale>
+
+  std::locale::global(std::locale("en_US.UTF-8"));
+  auto s = fmt::format("{:L}", 1000000);  // s == "1,000,000"
+
 .. _format-api:
 
 Format API
 ==========
 
 ``fmt/format.h`` defines the full format API providing compile-time format
-string checks, output iterator and user-defined type support.
+string checks, wide string, output iterator and user-defined type support.
 
 Compile-time Format String Checks
 ---------------------------------
 
-Compile-time checks are supported for built-in and string types as well as
-user-defined types with ``constexpr`` ``parse`` functions in their ``formatter``
-specializations.
+Compile-time checks are enabled when using ``FMT_STRING``. They support built-in
+and string types as well as user-defined types with ``constexpr`` ``parse``
+functions in their ``formatter`` specializations.
 
 .. doxygendefine:: FMT_STRING
 
+.. _udt:
+
 Formatting User-defined Types
 -----------------------------
 
@@ -119,6 +173,7 @@
 
     // Parses format specifications of the form ['f' | 'e'].
     constexpr auto parse(format_parse_context& ctx) {
+    // auto parse(format_parse_context &ctx) -> decltype(ctx.begin()) // c++11
       // [ctx.begin(), ctx.end()) is a character range that contains a part of
       // the format string starting from the format specifications to be parsed,
       // e.g. in
@@ -146,6 +201,7 @@
     // stored in this formatter.
     template <typename FormatContext>
     auto format(const point& p, FormatContext& ctx) {
+    // auto format(const point &p, FormatContext &ctx) -> decltype(ctx.out()) // c++11
       // ctx.out() is an output iterator to write to.
       return format_to(
           ctx.out(),
@@ -165,8 +221,7 @@
 
   enum class color {red, green, blue};
 
-  template <>
-  struct fmt::formatter<color>: formatter<string_view> {
+  template <> struct fmt::formatter<color>: formatter<string_view> {
     // parse is inherited from formatter<string_view>.
     template <typename FormatContext>
     auto format(color c, FormatContext& ctx) {
@@ -180,6 +235,15 @@
     }
   };
 
+Since ``parse`` is inherited from ``formatter<string_view>`` it will recognize
+all string format specifications, for example
+
+.. code-block:: c++
+
+   fmt::format("{:>10}", color::blue)
+
+will return ``"      blue"``.
+
 You can also write a formatter for a hierarchy of classes::
 
   #include <type_traits>
@@ -209,6 +273,10 @@
     fmt::print("{}", a); // prints "B"
   }
 
+If a type provides both a ``formatter`` specialization and an implicit
+conversion to a formattable type, the specialization takes precedence over the
+conversion.
+
 .. doxygenclass:: fmt::basic_format_parse_context
    :members:
 
@@ -216,7 +284,7 @@
 -----------------------
 
 .. doxygenfunction:: fmt::format_to(OutputIt, const S&, Args&&...)
-.. doxygenfunction:: fmt::format_to_n(OutputIt, std::size_t, string_view, Args&&...)
+.. doxygenfunction:: fmt::format_to_n(OutputIt, size_t, const S&, const Args&...)
 .. doxygenstruct:: fmt::format_to_n_result
    :members:
 
@@ -225,9 +293,9 @@
 
 The following user-defined literals are defined in ``fmt/format.h``.
 
-.. doxygenfunction:: operator""_format(const char *, std::size_t)
+.. doxygenfunction:: operator""_format(const char *, size_t)
 
-.. doxygenfunction:: operator""_a(const char *, std::size_t)
+.. doxygenfunction:: operator""_a(const char *, size_t)
 
 Utilities
 ---------
@@ -236,7 +304,9 @@
 
 .. doxygentypedef:: fmt::char_t
 
-.. doxygenfunction:: fmt::formatted_size(string_view, const Args&...)
+.. doxygenfunction:: fmt::ptr(const T *)
+.. doxygenfunction:: fmt::ptr(const std::unique_ptr<T>&)
+.. doxygenfunction:: fmt::ptr(const std::shared_ptr<T>&)
 
 .. doxygenfunction:: fmt::to_string(const T&)
 
@@ -244,9 +314,12 @@
 
 .. doxygenfunction:: fmt::to_string_view(const Char *)
 
-.. doxygenfunction:: fmt::join(const Range&, string_view)
+.. doxygenfunction:: fmt::join(Range&&, string_view)
 
-.. doxygenfunction:: fmt::join(It, It, string_view)
+.. doxygenfunction:: fmt::join(It, Sentinel, string_view)
+
+.. doxygenclass:: fmt::detail::buffer
+   :members:
 
 .. doxygenclass:: fmt::basic_memory_buffer
    :protected-members:
@@ -267,8 +340,6 @@
 .. doxygenclass:: fmt::windows_error
    :members:
 
-.. _formatstrings:
-
 Custom Allocators
 -----------------
 
@@ -299,54 +370,10 @@
       return vformat(alloc, format_str, fmt::make_format_args(args...));
     }
 
-The allocator will be used for the output container only. If you are using named
-arguments, the container that stores pointers to them will be allocated using
-the default allocator. Also floating-point formatting falls back on ``sprintf``
-which may do allocations.
-
-Custom Formatting of Built-in Types
------------------------------------
-
-It is possible to change the way arguments are formatted by providing a
-custom argument formatter class::
-
-  using arg_formatter = fmt::arg_formatter<fmt::buffer_range<char>>;
-
-  // A custom argument formatter that formats negative integers as unsigned
-  // with the ``x`` format specifier.
-  class custom_arg_formatter : public arg_formatter {
-   public:
-    custom_arg_formatter(fmt::format_context& ctx,
-                         fmt::format_parse_context* parse_ctx = nullptr,
-                         fmt::format_specs* spec = nullptr)
-      : arg_formatter(ctx, parse_ctx, spec) {}
-
-    using arg_formatter::operator();
-
-    auto operator()(int value) {
-      if (specs() && specs()->type == 'x')
-        return (*this)(static_cast<unsigned>(value)); // convert to unsigned and format
-      return arg_formatter::operator()(value);
-    }
-  };
-
-  std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
-    fmt::memory_buffer buffer;
-    // Pass custom argument formatter as a template arg to vformat_to.
-    fmt::vformat_to<custom_arg_formatter>(buffer, format_str, args);
-    return fmt::to_string(buffer);
-  }
-
-  template <typename ...Args>
-  inline std::string custom_format(
-      fmt::string_view format_str, const Args&... args) {
-    return custom_vformat(format_str, fmt::make_format_args(args...));
-  }
-
-  std::string s = custom_format("{:x}", -42); // s == "ffffffd6"
-
-.. doxygenclass:: fmt::arg_formatter
-   :members:
+The allocator will be used for the output container only. Formatting functions
+normally don't do any allocations for built-in and string types except for
+non-default floating-point formatting that occasionally falls back on
+``sprintf``.
 
 .. _ranges-api:
 
@@ -386,11 +413,36 @@
 
   std::time_t t = std::time(nullptr);
   // Prints "The date is 2016-04-29." (with the current date)
-  fmt::print("The date is {:%Y-%m-%d}.", *std::localtime(&t));
+  fmt::print("The date is {:%Y-%m-%d}.", fmt::localtime(t));
 
 The format string syntax is described in the documentation of
 `strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
 
+.. _compile-api:
+
+Format string compilation
+=========================
+
+``fmt/compile.h`` provides format string compilation support when using
+``FMT_COMPILE``. Format strings are parsed, checked and converted
+into efficient formatting code at compile-time.
+This supports arguments of built-in and string types as well as user-defined types
+with ``constexpr`` ``parse`` functions in their ``formatter`` specializations.
+Format string compilation can generate more binary code compared to the default
+API and is only recommended in places where formatting is a performance
+bottleneck.
+
+.. doxygendefine:: FMT_COMPILE
+
+.. _color-api:
+
+Terminal color and text style
+=============================
+
+``fmt/color.h`` provides support for terminal color and text style output.
+
+.. doxygenfunction:: print(const text_style&, const S&, const Args&...)
+
 .. _ostream-api:
 
 ``std::ostream`` Support
@@ -435,3 +487,19 @@
 .. doxygenfunction:: fprintf(std::basic_ostream<Char>&, const S&, const Args&...)
 
 .. doxygenfunction:: sprintf(const S&, const Args&...)
+
+Compatibility with C++20 ``std::format``
+========================================
+
+{fmt} implements nearly all of the `C++20 formatting library
+<https://en.cppreference.com/w/cpp/utility/format>`_ with the following
+differences:
+
+* Names are defined in the ``fmt`` namespace instead of ``std`` to avoid
+  collisions with standard library implementations.
+* The ``'L'`` format specifier cannot be combined with presentation specifiers
+  yet.
+* Width calculation doesn't use grapheme clusterization. The latter has been
+  implemented in a separate branch but hasn't been integrated yet.
+* Chrono formatting doesn't support C++20 date types since they are not provided
+  by standard library implementations.
diff --git a/doc/build.py b/doc/build.py
index 2f0c8b8..4651756 100755
--- a/doc/build.py
+++ b/doc/build.py
@@ -6,20 +6,10 @@
 from subprocess import check_call, check_output, CalledProcessError, Popen, PIPE
 from distutils.version import LooseVersion
 
-versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0', '5.1.0', '5.2.0', '5.2.1', '5.3.0', '6.0.0', '6.1.0', '6.1.1']
+versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0', '5.1.0', '5.2.0', '5.2.1', '5.3.0', '6.0.0', '6.1.0', '6.1.1', '6.1.2', '6.2.0', '6.2.1', '7.0.0', '7.0.1', '7.0.2', '7.0.3', '7.1.0', '7.1.1', '7.1.2', '7.1.3']
 
 def pip_install(package, commit=None, **kwargs):
   "Install package using pip."
-  min_version = kwargs.get('min_version')
-  if min_version:
-    from pkg_resources import get_distribution, DistributionNotFound
-    try:
-      installed_version = get_distribution(os.path.basename(package)).version
-      if LooseVersion(installed_version) >= min_version:
-        print('{} {} already installed'.format(package, min_version))
-        return
-    except DistributionNotFound:
-      pass
   if commit:
     package = 'git+https://github.com/{0}.git@{1}'.format(package, commit)
   print('Installing {0}'.format(package))
@@ -52,12 +42,11 @@
       check_call(['pip', 'install', '--upgrade', 'distribute'])
   except DistributionNotFound:
     pass
-  # Install Sphinx and Breathe.
-  pip_install('sphinx-doc/sphinx', '12b83372ac9316e8cbe86e7fed889296a4cc29ee',
-              min_version='1.4.1.dev20160531')
+  # Install Sphinx and Breathe. Require the exact version of Sphinx which is
+  # compatible with Breathe.
+  pip_install('sphinx-doc/sphinx', '12b83372ac9316e8cbe86e7fed889296a4cc29ee')
   pip_install('michaeljones/breathe',
-              '129222318f7c8f865d2631e7da7b033567e7f56a',
-              min_version='4.2.0')
+              '129222318f7c8f865d2631e7da7b033567e7f56a')
 
 def build_docs(version='dev', **kwargs):
   doc_dir = kwargs.get('doc_dir', os.path.dirname(os.path.realpath(__file__)))
@@ -74,8 +63,8 @@
       GENERATE_MAN      = NO
       GENERATE_RTF      = NO
       CASE_SENSE_NAMES  = NO
-      INPUT             = {0}/core.h {0}/format.h {0}/ostream.h \
-                          {0}/printf.h {0}/time.h
+      INPUT             = {0}/chrono.h {0}/color.h {0}/core.h {0}/compile.h \
+                          {0}/format.h {0}/os.h {0}/ostream.h {0}/printf.h
       QUIET             = YES
       JAVADOC_AUTOBRIEF = YES
       AUTOLINK_SUPPORT  = NO
@@ -95,7 +84,8 @@
                           "FMT_END_NAMESPACE=}}" \
                           "FMT_STRING_ALIAS=1" \
                           "FMT_ENABLE_IF(B)="
-      EXCLUDE_SYMBOLS   = fmt::internal::* StringValue write_str
+      EXCLUDE_SYMBOLS   = fmt::formatter fmt::printf_formatter fmt::arg_join \
+                          fmt::basic_format_arg::handle
     '''.format(include_dir, doxyxml_dir).encode('UTF-8'))
   if p.returncode != 0:
     raise CalledProcessError(p.returncode, cmd)
diff --git a/doc/index.rst b/doc/index.rst
index cbc9154..58f2929 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -10,7 +10,7 @@
      <div class="panel-heading">What users say:</div>
      <div class="panel-body">
        Thanks for creating this library. It’s been a hole in C++ for
-       aa long time. I’ve used both <code>boost::format</code> and
+       a long time. I’ve used both <code>boost::format</code> and
        <code>loki::SPrintf</code>, and neither felt like the right answer.
        This does.
      </div>
@@ -22,8 +22,8 @@
 ----------
 
 The format API is similar in spirit to the C ``printf`` family of function but
-is safer, simpler and serveral times `faster
-<http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_
+is safer, simpler and several times `faster
+<https://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_
 than common standard library implementations.
 The `format string syntax <syntax.html>`_ is similar to the one used by
 `str.format <http://docs.python.org/3/library/stdtypes.html#str.format>`_ in
@@ -48,21 +48,19 @@
 
   fmt::print(stderr, "System error code = {}\n", errno);
 
-The file argument can be omitted in which case the function prints to
-``stdout``:
+If you omit the file argument the function will print to ``stdout``:
 
 .. code:: c++
 
   fmt::print("Don't {}\n", "panic");
 
-The Format API also supports positional arguments useful for localization:
+The format API also supports positional arguments useful for localization:
 
 .. code:: c++
 
   fmt::print("I'd rather be {1} than {0}.", "right", "happy");
 
-Named arguments can be created with ``fmt::arg``. This makes it easier to track 
-what goes where when multiple arguments are being formatted:
+You can pass named arguments with ``fmt::arg``:
 
 .. code:: c++
 
@@ -91,16 +89,17 @@
 
   fmt::format("The answer is {:d}", "forty-two");
 
-throws a ``format_error`` exception with description "unknown format code 'd' for
-string", because the argument ``"forty-two"`` is a string while the format code
-``d`` only applies to integers, while
+throws the ``format_error`` exception because the argument ``"forty-two"`` is a
+string while the format code ``d`` only applies to integers.
+
+The code
 
 .. code:: c++
 
   format(FMT_STRING("The answer is {:d}"), "forty-two");
 
-reports a compile-time error for the same reason on compilers that support
-relaxed ``constexpr``. See `here <api.html#c.fmt>`_ for details.
+reports a compile-time error on compilers that support relaxed ``constexpr``.
+See `here <api.html#c.fmt>`_ for details.
 
 The following code
 
@@ -117,13 +116,13 @@
 
 For comparison, writing a wide character to ``std::ostream`` results in
 its numeric value being written to the stream (i.e. 1070 instead of letter 'ю'
-which is represented by ``L'\x42e'`` if we use Unicode) which is rarely what is
-needed.
+which is represented by ``L'\x42e'`` if we use Unicode) which is rarely
+desirable.
 
 Compact Binary Code
 -------------------
 
-The library is designed to produce compact per-call compiled code. For example
+The library produces compact per-call compiled code. For example
 (`godbolt <https://godbolt.org/g/TZU4KF>`_),
 
 .. code:: c++
@@ -144,8 +143,8 @@
      mov rcx, rsp
      mov edi, offset .L.str
      mov esi, 17
-     mov edx, 2
-     call fmt::v5::vprint(fmt::v5::basic_string_view<char>, fmt::v5::format_args)
+     mov edx, 1
+     call fmt::v7::vprint(fmt::v7::basic_string_view<char>, fmt::v7::format_args)
      xor eax, eax
      add rsp, 24
      ret
@@ -167,20 +166,19 @@
 * deleted functions
 * alias templates
 
-These are available since GCC 4.8, Clang 3.0 and MSVC 19.0 (2015). For older
-compilers use {fmt} `version 4.x
-<https://github.com/fmtlib/fmt/releases/tag/4.1.0>`_ which continues to be
-maintained and only requires C++98.
+These are available in GCC 4.8, Clang 3.0, MSVC 19.0 (2015) and more recent
+compiler version. For older compilers use {fmt} `version 4.x
+<https://github.com/fmtlib/fmt/releases/tag/4.1.0>`_ which is maintained and
+only requires C++98.
 
-The output of all formatting functions is consistent across platforms. In
-particular, formatting a floating-point infinity always gives ``inf`` while the
-output of ``printf`` is platform-dependent. For example,
+The output of all formatting functions is consistent across platforms.
+For example,
 
 .. code::
 
   fmt::print("{}", std::numeric_limits<double>::infinity());
 
-always prints ``inf``.
+always prints ``inf`` while the output of ``printf`` is platform-dependent.
 
 .. _ease-of-use:
 
diff --git a/doc/syntax.rst b/doc/syntax.rst
index 1f25dac..8265f70 100644
--- a/doc/syntax.rst
+++ b/doc/syntax.rst
@@ -76,19 +76,19 @@
 
 .. productionlist:: sf
    format_spec: [[`fill`]`align`][`sign`]["#"]["0"][`width`]["." `precision`][`type`]
-   fill: <a character other than '{', '}' or '\0'>
-   align: "<" | ">" | "=" | "^"
+   fill: <a character other than '{' or '}'>
+   align: "<" | ">" | "^"
    sign: "+" | "-" | " "
-   width: `integer` | "{" `arg_id` "}"
-   precision: `integer` | "{" `arg_id` "}"
-   type: `int_type` | "a" | "A" | "c" | "e" | "E" | "f" | "F" | "g" | "G" | "p" | "s"
-   int_type: "b" | "B" | "d" | "n" | "o" | "x" | "X"
+   width: `integer` | "{" [`arg_id`] "}"
+   precision: `integer` | "{" [`arg_id`] "}"
+   type: `int_type` | "a" | "A" | "c" | "e" | "E" | "f" | "F" | "g" | "G" | "L" | "p" | "s"
+   int_type: "b" | "B" | "d" | "o" | "x" | "X"
 
-The *fill* character can be any character other than '{', '}' or '\\0'. The
-presence of a fill character is signaled by the character following it, which
-must be one of the alignment options.  If the second character of *format_spec*
-is not a valid alignment option, then it is assumed that both the fill character
-and the alignment option are absent.
+The *fill* character can be any Unicode code point other than ``'{'`` or
+``'}'``. The presence of a fill character is signaled by the character following
+it, which must be one of the alignment options. If the second character of
+*format_spec* is not a valid alignment option, then it is assumed that both the
+fill character and the alignment option are absent.
 
 The meaning of the various alignment options is as follows:
 
@@ -143,7 +143,7 @@
 .. ifconfig:: False
 
    The ``','`` option signals the use of a comma for a thousands separator.
-   For a locale aware separator, use the ``'n'`` integer presentation type
+   For a locale aware separator, use the ``'L'`` integer presentation type
    instead.
 
 *width* is a decimal integer defining the minimum field width.  If not
@@ -214,9 +214,9 @@
 |         | ``'#'`` option with this type adds the prefix ``"0X"``   |
 |         | to the output value.                                     |
 +---------+----------------------------------------------------------+
-| ``'n'`` | Number. This is the same as ``'d'``, except that it uses |
-|         | the current locale setting to insert the appropriate     |
-|         | number separator characters.                             |
+| ``'L'`` | Locale-specific format. This is the same as ``'d'``,     |
+|         | except that it uses the current locale setting to insert |
+|         | the appropriate number separator characters.             |
 +---------+----------------------------------------------------------+
 | none    | The same as ``'d'``.                                     |
 +---------+----------------------------------------------------------+
@@ -261,13 +261,9 @@
 |         | ``'E'`` if the number gets too large. The                |
 |         | representations of infinity and NaN are uppercased, too. |
 +---------+----------------------------------------------------------+
-| ``'n'`` | Number. This is the same as ``'g'``, except that it uses |
-|         | the current locale setting to insert the appropriate     |
-|         | number separator characters.                             |
-+---------+----------------------------------------------------------+
-| ``'%'`` | Fixed point as a percentage. This is similar to ``'f'``, |
-|         | but the argument is multiplied by 100 and a percent sign |
-|         | ``%`` is appended.                                       |
+| ``'L'`` | Locale-specific format. This is the same as ``'g'``,     |
+|         | except that it uses the current locale setting to insert |
+|         | the appropriate number separator characters.             |
 +---------+----------------------------------------------------------+
 | none    | Similar to ``'g'``, except that fixed-point notation,    |
 |         | when used, has at least one digit past the decimal       |
@@ -324,79 +320,94 @@
 
 Accessing arguments by position::
 
-   format("{0}, {1}, {2}", 'a', 'b', 'c');
+   fmt::format("{0}, {1}, {2}", 'a', 'b', 'c');
    // Result: "a, b, c"
-   format("{}, {}, {}", 'a', 'b', 'c');
+   fmt::format("{}, {}, {}", 'a', 'b', 'c');
    // Result: "a, b, c"
-   format("{2}, {1}, {0}", 'a', 'b', 'c');
+   fmt::format("{2}, {1}, {0}", 'a', 'b', 'c');
    // Result: "c, b, a"
-   format("{0}{1}{0}", "abra", "cad");  // arguments' indices can be repeated
+   fmt::format("{0}{1}{0}", "abra", "cad");  // arguments' indices can be repeated
    // Result: "abracadabra"
 
 Aligning the text and specifying a width::
 
-   format("{:<30}", "left aligned");
+   fmt::format("{:<30}", "left aligned");
    // Result: "left aligned                  "
-   format("{:>30}", "right aligned");
+   fmt::format("{:>30}", "right aligned");
    // Result: "                 right aligned"
-   format("{:^30}", "centered");
+   fmt::format("{:^30}", "centered");
    // Result: "           centered           "
-   format("{:*^30}", "centered");  // use '*' as a fill char
+   fmt::format("{:*^30}", "centered");  // use '*' as a fill char
    // Result: "***********centered***********"
 
 Dynamic width::
 
-   format("{:<{}}", "left aligned", 30);
+   fmt::format("{:<{}}", "left aligned", 30);
    // Result: "left aligned                  "
 
 Dynamic precision::
 
-   format("{:.{}f}", 3.14, 1);
+   fmt::format("{:.{}f}", 3.14, 1);
    // Result: "3.1"
 
 Replacing ``%+f``, ``%-f``, and ``% f`` and specifying a sign::
 
-   format("{:+f}; {:+f}", 3.14, -3.14);  // show it always
+   fmt::format("{:+f}; {:+f}", 3.14, -3.14);  // show it always
    // Result: "+3.140000; -3.140000"
-   format("{: f}; {: f}", 3.14, -3.14);  // show a space for positive numbers
+   fmt::format("{: f}; {: f}", 3.14, -3.14);  // show a space for positive numbers
    // Result: " 3.140000; -3.140000"
-   format("{:-f}; {:-f}", 3.14, -3.14);  // show only the minus -- same as '{:f}; {:f}'
+   fmt::format("{:-f}; {:-f}", 3.14, -3.14);  // show only the minus -- same as '{:f}; {:f}'
    // Result: "3.140000; -3.140000"
 
-As a percentage::
-
-   format("{0:f} or {0:%}", .635);
-   // Result: "0.635000 or 63.500000%"
-   format("{:*^{}.{}%}", 1., 15, 2); // With fill, dynamic width and dynamic precision.
-   // Result: "****100.00%****"
-
 Replacing ``%x`` and ``%o`` and converting the value to different bases::
 
-   format("int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
+   fmt::format("int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
    // Result: "int: 42;  hex: 2a;  oct: 52; bin: 101010"
    // with 0x or 0 or 0b as prefix:
-   format("int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}", 42);
+   fmt::format("int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}", 42);
    // Result: "int: 42;  hex: 0x2a;  oct: 052;  bin: 0b101010"
 
 Padded hex byte with prefix and always prints both hex characters::
 
-   format("{:#04x}", 0);
+   fmt::format("{:#04x}", 0);
    // Result: "0x00"
 
+Box drawing using Unicode fill::
+
+   fmt::print(
+     "┌{0:─^{2}}┐\n"
+     "│{1: ^{2}}│\n"
+     "└{0:─^{2}}┘\n", "", "Hello, world!", 20);
+
+prints::
+
+   ┌────────────────────┐
+   │   Hello, world!    │
+   └────────────────────┘
+
+Using type-specific formatting::
+
+   #include <fmt/chrono.h>
+
+   auto t = tm();
+   t.tm_year = 2010 - 1900;
+   t.tm_mon = 6;
+   t.tm_mday = 4;
+   t.tm_hour = 12;
+   t.tm_min = 15;
+   t.tm_sec = 58;
+   fmt::print("{:%Y-%m-%d %H:%M:%S}", t);
+   // Prints: 2010-08-04 12:15:58
+
+Using the comma as a thousands separator::
+
+   #include <fmt/locale.h>
+
+   auto s = fmt::format(std::locale("en_US.UTF-8"), "{:L}", 1234567890);
+   // s == "1,234,567,890"
+
 .. ifconfig:: False
 
-   Using the comma as a thousands separator::
-
-      format("{:,}", 1234567890);
-      '1,234,567,890'
-
-   Using type-specific formatting::
-
-      >>> import datetime
-      >>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
-      Format("{:%Y-%m-%d %H:%M:%S}") << d)
-      '2010-07-04 12:15:58'
-
    Nesting arguments and more complex examples::
 
       >>> for align, text in zip('<^>', ['left', 'center', 'right']):
diff --git a/doc/usage.rst b/doc/usage.rst
index dacb4f0..435afd5 100644
--- a/doc/usage.rst
+++ b/doc/usage.rst
@@ -52,6 +52,14 @@
 
 __ http://en.wikipedia.org/wiki/Library_%28computing%29#Shared_libraries
 
+
+To build a `static library` with position independent code (required if the main
+consumer of the fmt library is a shared library i.e. a Python extension) set the
+``CMAKE_POSITION_INDEPENDENT_CODE`` CMake variable to ``TRUE``::
+
+  cmake -DCMAKE_POSITION_INDEPENDENT_CODE=TRUE ...
+
+
 Installing the Library
 ======================
 
@@ -83,6 +91,49 @@
 
    target_link_libraries(<your-target> PRIVATE fmt::fmt-header-only)
 
+Usage with build2
+=================
+
+You can use `build2 <https://build2.org>`_, a dependency manager and a
+build-system combined, to use ``fmt``.
+
+Currently this package is available in these package repositories:
+
+- **https://cppget.org/fmt/** for released and published versions.
+- `The git repository with the sources of the build2 package of fmt <https://github.com/build2-packaging/fmt.git>`_
+  for unreleased or custom revisions of ``fmt``.
+
+**Usage:**
+
+- ``build2`` package name: ``fmt``
+- Library target name : ``lib{fmt}``
+
+For example, to make your ``build2`` project depend on ``fmt``:
+
+- Add one of the repositories to your configurations, or in your
+  ``repositories.manifest``, if not already there::
+
+    :
+    role: prerequisite
+    location: https://pkg.cppget.org/1/stable
+
+- Add this package as a dependency to your ``./manifest`` file
+  (example for ``v7.0.x``)::
+
+    depends: fmt ~7.0.0
+
+- Import the target and use it as a prerequisite to your own target
+  using `fmt` in the appropriate ``buildfile``::
+
+    import fmt = fmt%lib{fmt}
+    lib{mylib} : cxx{**} ... $fmt
+
+Then build your project as usual with `b` or `bdep update`.
+
+For ``build2`` newcomers or to get more details and use cases, you can read the
+``build2``
+`toolchain introduction <https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml>`_.
+
 Building the Documentation
 ==========================
 
@@ -114,6 +165,34 @@
 
   conda install -c conda-forge fmt
 
+Vcpkg
+=====
+
+You can download and install fmt using the `vcpkg
+<https://github.com/Microsoft/vcpkg>`__ dependency manager::
+
+  git clone https://github.com/Microsoft/vcpkg.git
+  cd vcpkg
+  ./bootstrap-vcpkg.sh
+  ./vcpkg integrate install
+  ./vcpkg install fmt
+
+The fmt port in vcpkg is kept up to date by Microsoft team members and community
+contributors. If the version is out of date, please `create an issue or pull
+request <https://github.com/Microsoft/vcpkg>`__ on the vcpkg repository.
+
+LHelper
+=======
+
+You can download and install fmt using
+`lhelper <https://github.com/franko/lhelper>`__ dependency manager::
+
+  lhelper activate <some-environment>
+  lhelper install fmt
+
+All the recipes for lhelper are kept in the
+`lhelper's recipe <https://github.com/franko/lhelper-recipes>`__ repository.
+
 Android NDK
 ===========
 
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index 9abe7c4..1a3b8d5 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -8,14 +8,14 @@
 #ifndef FMT_CHRONO_H_
 #define FMT_CHRONO_H_
 
-#include "format.h"
-#include "locale.h"
-
 #include <chrono>
 #include <ctime>
 #include <locale>
 #include <sstream>
 
+#include "format.h"
+#include "locale.h"
+
 FMT_BEGIN_NAMESPACE
 
 // Enable safe chrono durations, unless explicitly disabled.
@@ -48,7 +48,7 @@
     // From fits in To without any problem.
   } else {
     // From does not always fit in To, resort to a dynamic check.
-    if (from < T::min() || from > T::max()) {
+    if (from < (T::min)() || from > (T::max)()) {
       // outside range.
       ec = 1;
       return {};
@@ -72,43 +72,27 @@
   static_assert(F::is_integer, "From must be integral");
   static_assert(T::is_integer, "To must be integral");
 
-  if (F::is_signed && !T::is_signed) {
+  if (detail::const_check(F::is_signed && !T::is_signed)) {
     // From may be negative, not allowed!
-    if (fmt::internal::is_negative(from)) {
+    if (fmt::detail::is_negative(from)) {
       ec = 1;
       return {};
     }
-
     // From is positive. Can it always fit in To?
-    if (F::digits <= T::digits) {
-      // yes, From always fits in To.
-    } else {
-      // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
-        ec = 1;
-        return {};
-      }
+    if (F::digits > T::digits &&
+        from > static_cast<From>(detail::max_value<To>())) {
+      ec = 1;
+      return {};
     }
   }
 
-  if (!F::is_signed && T::is_signed) {
-    // can from be held in To?
-    if (F::digits < T::digits) {
-      // yes, From always fits in To.
-    } else {
-      // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
-        // outside range.
-        ec = 1;
-        return {};
-      }
-    }
+  if (!F::is_signed && T::is_signed && F::digits >= T::digits &&
+      from > static_cast<From>(detail::max_value<To>())) {
+    ec = 1;
+    return {};
   }
-
-  // reaching here means all is ok for lossless conversion.
-  return static_cast<To>(from);
-
-}  // function
+  return static_cast<To>(from);  // Lossless conversion.
+}
 
 template <typename To, typename From,
           FMT_ENABLE_IF(std::is_same<From, To>::value)>
@@ -141,7 +125,7 @@
 
   // catch the only happy case
   if (std::isfinite(from)) {
-    if (from >= T::lowest() && from <= T::max()) {
+    if (from >= T::lowest() && from <= (T::max)()) {
       return static_cast<To>(from);
     }
     // not within range.
@@ -190,17 +174,16 @@
   // safe conversion to IntermediateRep
   IntermediateRep count =
       lossless_integral_conversion<IntermediateRep>(from.count(), ec);
-  if (ec) {
-    return {};
-  }
+  if (ec) return {};
   // multiply with Factor::num without overflow or underflow
-  if (Factor::num != 1) {
-    const auto max1 = internal::max_value<IntermediateRep>() / Factor::num;
+  if (detail::const_check(Factor::num != 1)) {
+    const auto max1 = detail::max_value<IntermediateRep>() / Factor::num;
     if (count > max1) {
       ec = 1;
       return {};
     }
-    const auto min1 = std::numeric_limits<IntermediateRep>::min() / Factor::num;
+    const auto min1 =
+        (std::numeric_limits<IntermediateRep>::min)() / Factor::num;
     if (count < min1) {
       ec = 1;
       return {};
@@ -208,17 +191,9 @@
     count *= Factor::num;
   }
 
-  // this can't go wrong, right? den>0 is checked earlier.
-  if (Factor::den != 1) {
-    count /= Factor::den;
-  }
-  // convert to the to type, safely
-  using ToRep = typename To::rep;
-  const ToRep tocount = lossless_integral_conversion<ToRep>(count, ec);
-  if (ec) {
-    return {};
-  }
-  return To{tocount};
+  if (detail::const_check(Factor::den != 1)) count /= Factor::den;
+  auto tocount = lossless_integral_conversion<typename To::rep>(count, ec);
+  return ec ? To() : To(tocount);
 }
 
 /**
@@ -269,7 +244,7 @@
 
   // multiply with Factor::num without overflow or underflow
   if (Factor::num != 1) {
-    constexpr auto max1 = internal::max_value<IntermediateRep>() /
+    constexpr auto max1 = detail::max_value<IntermediateRep>() /
                           static_cast<IntermediateRep>(Factor::num);
     if (count > max1) {
       ec = 1;
@@ -306,12 +281,12 @@
 // Usage: f FMT_NOMACRO()
 #define FMT_NOMACRO
 
-namespace internal {
+namespace detail {
 inline null<> localtime_r FMT_NOMACRO(...) { return null<>(); }
 inline null<> localtime_s(...) { return null<>(); }
 inline null<> gmtime_r(...) { return null<>(); }
 inline null<> gmtime_s(...) { return null<>(); }
-}  // namespace internal
+}  // namespace detail
 
 // Thread-safe replacement for std::localtime
 inline std::tm localtime(std::time_t time) {
@@ -322,22 +297,22 @@
     dispatcher(std::time_t t) : time_(t) {}
 
     bool run() {
-      using namespace fmt::internal;
+      using namespace fmt::detail;
       return handle(localtime_r(&time_, &tm_));
     }
 
     bool handle(std::tm* tm) { return tm != nullptr; }
 
-    bool handle(internal::null<>) {
-      using namespace fmt::internal;
+    bool handle(detail::null<>) {
+      using namespace fmt::detail;
       return fallback(localtime_s(&tm_, &time_));
     }
 
     bool fallback(int res) { return res == 0; }
 
 #if !FMT_MSC_VER
-    bool fallback(internal::null<>) {
-      using namespace fmt::internal;
+    bool fallback(detail::null<>) {
+      using namespace fmt::detail;
       std::tm* tm = std::localtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
@@ -350,6 +325,11 @@
   return lt.tm_;
 }
 
+inline std::tm localtime(
+    std::chrono::time_point<std::chrono::system_clock> time_point) {
+  return localtime(std::chrono::system_clock::to_time_t(time_point));
+}
+
 // Thread-safe replacement for std::gmtime
 inline std::tm gmtime(std::time_t time) {
   struct dispatcher {
@@ -359,21 +339,21 @@
     dispatcher(std::time_t t) : time_(t) {}
 
     bool run() {
-      using namespace fmt::internal;
+      using namespace fmt::detail;
       return handle(gmtime_r(&time_, &tm_));
     }
 
     bool handle(std::tm* tm) { return tm != nullptr; }
 
-    bool handle(internal::null<>) {
-      using namespace fmt::internal;
+    bool handle(detail::null<>) {
+      using namespace fmt::detail;
       return fallback(gmtime_s(&tm_, &time_));
     }
 
     bool fallback(int res) { return res == 0; }
 
 #if !FMT_MSC_VER
-    bool fallback(internal::null<>) {
+    bool fallback(detail::null<>) {
       std::tm* tm = std::gmtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
@@ -386,17 +366,33 @@
   return gt.tm_;
 }
 
-namespace internal {
-inline std::size_t strftime(char* str, std::size_t count, const char* format,
-                            const std::tm* time) {
+inline std::tm gmtime(
+    std::chrono::time_point<std::chrono::system_clock> time_point) {
+  return gmtime(std::chrono::system_clock::to_time_t(time_point));
+}
+
+namespace detail {
+inline size_t strftime(char* str, size_t count, const char* format,
+                       const std::tm* time) {
   return std::strftime(str, count, format, time);
 }
 
-inline std::size_t strftime(wchar_t* str, std::size_t count,
-                            const wchar_t* format, const std::tm* time) {
+inline size_t strftime(wchar_t* str, size_t count, const wchar_t* format,
+                       const std::tm* time) {
   return std::wcsftime(str, count, format, time);
 }
-}  // namespace internal
+}  // namespace detail
+
+template <typename Char>
+struct formatter<std::chrono::time_point<std::chrono::system_clock>, Char>
+    : formatter<std::tm, Char> {
+  template <typename FormatContext>
+  auto format(std::chrono::time_point<std::chrono::system_clock> val,
+              FormatContext& ctx) -> decltype(ctx.out()) {
+    std::tm time = localtime(val);
+    return formatter<std::tm, Char>::format(time, ctx);
+  }
+};
 
 template <typename Char> struct formatter<std::tm, Char> {
   template <typename ParseContext>
@@ -405,7 +401,7 @@
     if (it != ctx.end() && *it == ':') ++it;
     auto end = it;
     while (end != ctx.end() && *end != '}') ++end;
-    tm_format.reserve(internal::to_unsigned(end - it + 1));
+    tm_format.reserve(detail::to_unsigned(end - it + 1));
     tm_format.append(it, end);
     tm_format.push_back('\0');
     return end;
@@ -414,11 +410,10 @@
   template <typename FormatContext>
   auto format(const std::tm& tm, FormatContext& ctx) -> decltype(ctx.out()) {
     basic_memory_buffer<Char> buf;
-    std::size_t start = buf.size();
+    size_t start = buf.size();
     for (;;) {
-      std::size_t size = buf.capacity() - start;
-      std::size_t count =
-          internal::strftime(&buf[start], size, &tm_format[0], &tm);
+      size_t size = buf.capacity() - start;
+      size_t count = detail::strftime(&buf[start], size, &tm_format[0], &tm);
       if (count != 0) {
         buf.resize(start + count);
         break;
@@ -430,7 +425,7 @@
         // https://github.com/fmtlib/fmt/issues/367
         break;
       }
-      const std::size_t MIN_GROWTH = 10;
+      const size_t MIN_GROWTH = 10;
       buf.reserve(buf.capacity() + (size > MIN_GROWTH ? size : MIN_GROWTH));
     }
     return std::copy(buf.begin(), buf.end(), ctx.out());
@@ -439,7 +434,7 @@
   basic_memory_buffer<Char> tm_format;
 };
 
-namespace internal {
+namespace detail {
 template <typename Period> FMT_CONSTEXPR const char* get_units() {
   return nullptr;
 }
@@ -495,12 +490,12 @@
       handler.on_text(ptr - 1, ptr);
       break;
     case 'n': {
-      const char newline[] = "\n";
+      const Char newline[] = {'\n'};
       handler.on_text(newline, newline + 1);
       break;
     }
     case 't': {
-      const char tab[] = "\t";
+      const Char tab[] = {'\t'};
       handler.on_text(tab, tab + 1);
       break;
     }
@@ -696,7 +691,7 @@
 
 template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
 inline T mod(T x, int y) {
-  return x % y;
+  return x % static_cast<T>(y);
 }
 template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
 inline T mod(T x, int y) {
@@ -759,18 +754,36 @@
   return std::chrono::duration<Rep, std::milli>(static_cast<Rep>(ms));
 }
 
-template <typename Rep, typename OutputIt>
-OutputIt format_chrono_duration_value(OutputIt out, Rep val, int precision) {
-  if (precision >= 0) return format_to(out, "{:.{}f}", val, precision);
-  return format_to(out, std::is_floating_point<Rep>::value ? "{:g}" : "{}",
+template <typename Char, typename Rep, typename OutputIt>
+OutputIt format_duration_value(OutputIt out, Rep val, int precision) {
+  const Char pr_f[] = {'{', ':', '.', '{', '}', 'f', '}', 0};
+  if (precision >= 0) return format_to(out, pr_f, val, precision);
+  const Char fp_f[] = {'{', ':', 'g', '}', 0};
+  const Char format[] = {'{', '}', 0};
+  return format_to(out, std::is_floating_point<Rep>::value ? fp_f : format,
                    val);
 }
+template <typename Char, typename OutputIt>
+OutputIt copy_unit(string_view unit, OutputIt out, Char) {
+  return std::copy(unit.begin(), unit.end(), out);
+}
 
-template <typename Period, typename OutputIt>
-static OutputIt format_chrono_duration_unit(OutputIt out) {
-  if (const char* unit = get_units<Period>()) return format_to(out, "{}", unit);
-  if (Period::den == 1) return format_to(out, "[{}]s", Period::num);
-  return format_to(out, "[{}/{}]s", Period::num, Period::den);
+template <typename OutputIt>
+OutputIt copy_unit(string_view unit, OutputIt out, wchar_t) {
+  // This works when wchar_t is UTF-32 because units only contain characters
+  // that have the same representation in UTF-16 and UTF-32.
+  utf8_to_utf16 u(unit);
+  return std::copy(u.c_str(), u.c_str() + u.size(), out);
+}
+
+template <typename Char, typename Period, typename OutputIt>
+OutputIt format_duration_unit(OutputIt out) {
+  if (const char* unit = get_units<Period>())
+    return copy_unit(string_view(unit), out, Char());
+  const Char num_f[] = {'[', '{', '}', ']', 's', 0};
+  if (const_check(Period::den == 1)) return format_to(out, num_f, Period::num);
+  const Char num_def_f[] = {'[', '{', '}', '/', '{', '}', ']', 's', 0};
+  return format_to(out, num_def_f, Period::num, Period::den);
 }
 
 template <typename FormatContext, typename OutputIt, typename Rep,
@@ -793,7 +806,10 @@
 
   explicit chrono_formatter(FormatContext& ctx, OutputIt o,
                             std::chrono::duration<Rep, Period> d)
-      : context(ctx), out(o), val(d.count()), negative(false) {
+      : context(ctx),
+        out(o),
+        val(static_cast<rep>(d.count())),
+        negative(false) {
     if (d.count() < 0) {
       val = 0 - val;
       negative = true;
@@ -859,22 +875,22 @@
     if (isnan(value)) return write_nan();
     uint32_or_64_or_128_t<int> n =
         to_unsigned(to_nonnegative_int(value, max_value<int>()));
-    int num_digits = internal::count_digits(n);
+    int num_digits = detail::count_digits(n);
     if (width > num_digits) out = std::fill_n(out, width - num_digits, '0');
-    out = format_decimal<char_type>(out, n, num_digits);
+    out = format_decimal<char_type>(out, n, num_digits).end;
   }
 
   void write_nan() { std::copy_n("nan", 3, out); }
   void write_pinf() { std::copy_n("inf", 3, out); }
   void write_ninf() { std::copy_n("-inf", 4, out); }
 
-  void format_localized(const tm& time, const char* format) {
+  void format_localized(const tm& time, char format, char modifier = 0) {
     if (isnan(val)) return write_nan();
     auto locale = context.locale().template get<std::locale>();
     auto& facet = std::use_facet<std::time_put<char_type>>(locale);
     std::basic_ostringstream<char_type> os;
     os.imbue(locale);
-    facet.put(os, os, ' ', &time, format, format + std::strlen(format));
+    facet.put(os, os, ' ', &time, format, modifier);
     auto str = os.str();
     std::copy(str.begin(), str.end(), out);
   }
@@ -904,7 +920,7 @@
     if (ns == numeric_system::standard) return write(hour(), 2);
     auto time = tm();
     time.tm_hour = to_nonnegative_int(hour(), 24);
-    format_localized(time, "%OH");
+    format_localized(time, 'H', 'O');
   }
 
   void on_12_hour(numeric_system ns) {
@@ -913,7 +929,7 @@
     if (ns == numeric_system::standard) return write(hour12(), 2);
     auto time = tm();
     time.tm_hour = to_nonnegative_int(hour12(), 12);
-    format_localized(time, "%OI");
+    format_localized(time, 'I', 'O');
   }
 
   void on_minute(numeric_system ns) {
@@ -922,7 +938,7 @@
     if (ns == numeric_system::standard) return write(minute(), 2);
     auto time = tm();
     time.tm_min = to_nonnegative_int(minute(), 60);
-    format_localized(time, "%OM");
+    format_localized(time, 'M', 'O');
   }
 
   void on_second(numeric_system ns) {
@@ -947,13 +963,12 @@
     }
     auto time = tm();
     time.tm_sec = to_nonnegative_int(second(), 60);
-    format_localized(time, "%OS");
+    format_localized(time, 'S', 'O');
   }
 
   void on_12_hour_time() {
     if (handle_nan_inf()) return;
-
-    format_localized(time(), "%r");
+    format_localized(time(), 'r');
   }
 
   void on_24_hour_time() {
@@ -977,25 +992,27 @@
 
   void on_am_pm() {
     if (handle_nan_inf()) return;
-    format_localized(time(), "%p");
+    format_localized(time(), 'p');
   }
 
   void on_duration_value() {
     if (handle_nan_inf()) return;
     write_sign();
-    out = format_chrono_duration_value(out, val, precision);
+    out = format_duration_value<char_type>(out, val, precision);
   }
 
-  void on_duration_unit() { out = format_chrono_duration_unit<Period>(out); }
+  void on_duration_unit() {
+    out = format_duration_unit<char_type, Period>(out);
+  }
 };
-}  // namespace internal
+}  // namespace detail
 
 template <typename Rep, typename Period, typename Char>
 struct formatter<std::chrono::duration<Rep, Period>, Char> {
  private:
   basic_format_specs<Char> specs;
   int precision;
-  using arg_ref_type = internal::arg_ref<Char>;
+  using arg_ref_type = detail::arg_ref<Char>;
   arg_ref_type width_ref;
   arg_ref_type precision_ref;
   mutable basic_string_view<Char> format_str;
@@ -1016,15 +1033,15 @@
       return arg_ref_type(arg_id);
     }
 
-    FMT_CONSTEXPR arg_ref_type make_arg_ref(internal::auto_id) {
+    FMT_CONSTEXPR arg_ref_type make_arg_ref(detail::auto_id) {
       return arg_ref_type(context.next_arg_id());
     }
 
     void on_error(const char* msg) { FMT_THROW(format_error(msg)); }
-    void on_fill(Char fill) { f.specs.fill[0] = fill; }
+    void on_fill(basic_string_view<Char> fill) { f.specs.fill = fill; }
     void on_align(align_t align) { f.specs.align = align; }
-    void on_width(unsigned width) { f.specs.width = width; }
-    void on_precision(unsigned _precision) { f.precision = _precision; }
+    void on_width(int width) { f.specs.width = width; }
+    void on_precision(int _precision) { f.precision = _precision; }
     void end_precision() {}
 
     template <typename Id> void on_dynamic_width(Id arg_id) {
@@ -1046,17 +1063,17 @@
     auto begin = ctx.begin(), end = ctx.end();
     if (begin == end || *begin == '}') return {begin, begin};
     spec_handler handler{*this, ctx, format_str};
-    begin = internal::parse_align(begin, end, handler);
+    begin = detail::parse_align(begin, end, handler);
     if (begin == end) return {begin, begin};
-    begin = internal::parse_width(begin, end, handler);
+    begin = detail::parse_width(begin, end, handler);
     if (begin == end) return {begin, begin};
     if (*begin == '.') {
       if (std::is_floating_point<Rep>::value)
-        begin = internal::parse_precision(begin, end, handler);
+        begin = detail::parse_precision(begin, end, handler);
       else
         handler.on_error("precision not allowed for this argument type");
     }
-    end = parse_chrono_format(begin, end, internal::chrono_format_checker());
+    end = parse_chrono_format(begin, end, detail::chrono_format_checker());
     return {begin, end};
   }
 
@@ -1067,7 +1084,7 @@
       -> decltype(ctx.begin()) {
     auto range = do_parse(ctx);
     format_str = basic_string_view<Char>(
-        &*range.begin, internal::to_unsigned(range.end - range.begin));
+        &*range.begin, detail::to_unsigned(range.end - range.begin));
     return range.end;
   }
 
@@ -1078,23 +1095,21 @@
     // is not specified.
     basic_memory_buffer<Char> buf;
     auto out = std::back_inserter(buf);
-    using range = internal::output_range<decltype(ctx.out()), Char>;
-    internal::basic_writer<range> w(range(ctx.out()));
-    internal::handle_dynamic_spec<internal::width_checker>(specs.width,
-                                                           width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
-        precision, precision_ref, ctx);
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref,
+                                                       ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(precision,
+                                                           precision_ref, ctx);
     if (begin == end || *begin == '}') {
-      out = internal::format_chrono_duration_value(out, d.count(), precision);
-      internal::format_chrono_duration_unit<Period>(out);
+      out = detail::format_duration_value<Char>(out, d.count(), precision);
+      detail::format_duration_unit<Char, Period>(out);
     } else {
-      internal::chrono_formatter<FormatContext, decltype(out), Rep, Period> f(
+      detail::chrono_formatter<FormatContext, decltype(out), Rep, Period> f(
           ctx, out, d);
       f.precision = precision;
       parse_chrono_format(begin, end, f);
     }
-    w.write(buf.data(), buf.size(), specs);
-    return w.out();
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
   }
 };
 
diff --git a/include/fmt/color.h b/include/fmt/color.h
index 362a95e..94e3419 100644
--- a/include/fmt/color.h
+++ b/include/fmt/color.h
@@ -198,7 +198,7 @@
   uint8_t b;
 };
 
-namespace internal {
+namespace detail {
 
 // color is a struct of either a rgb color or a terminal color.
 struct color_type {
@@ -221,7 +221,7 @@
     uint32_t rgb_color;
   } value;
 };
-}  // namespace internal
+}  // namespace detail
 
 // Experimental text formatting support.
 class text_style {
@@ -298,11 +298,11 @@
   FMT_CONSTEXPR bool has_emphasis() const FMT_NOEXCEPT {
     return static_cast<uint8_t>(ems) != 0;
   }
-  FMT_CONSTEXPR internal::color_type get_foreground() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR detail::color_type get_foreground() const FMT_NOEXCEPT {
     FMT_ASSERT(has_foreground(), "no foreground specified for this style");
     return foreground_color;
   }
-  FMT_CONSTEXPR internal::color_type get_background() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR detail::color_type get_background() const FMT_NOEXCEPT {
     FMT_ASSERT(has_background(), "no background specified for this style");
     return background_color;
   }
@@ -313,7 +313,7 @@
 
  private:
   FMT_CONSTEXPR text_style(bool is_foreground,
-                           internal::color_type text_color) FMT_NOEXCEPT
+                           detail::color_type text_color) FMT_NOEXCEPT
       : set_foreground_color(),
         set_background_color(),
         ems() {
@@ -326,23 +326,23 @@
     }
   }
 
-  friend FMT_CONSTEXPR_DECL text_style fg(internal::color_type foreground)
+  friend FMT_CONSTEXPR_DECL text_style fg(detail::color_type foreground)
       FMT_NOEXCEPT;
-  friend FMT_CONSTEXPR_DECL text_style bg(internal::color_type background)
+  friend FMT_CONSTEXPR_DECL text_style bg(detail::color_type background)
       FMT_NOEXCEPT;
 
-  internal::color_type foreground_color;
-  internal::color_type background_color;
+  detail::color_type foreground_color;
+  detail::color_type background_color;
   bool set_foreground_color;
   bool set_background_color;
   emphasis ems;
 };
 
-FMT_CONSTEXPR text_style fg(internal::color_type foreground) FMT_NOEXCEPT {
+FMT_CONSTEXPR text_style fg(detail::color_type foreground) FMT_NOEXCEPT {
   return text_style(/*is_foreground=*/true, foreground);
 }
 
-FMT_CONSTEXPR text_style bg(internal::color_type background) FMT_NOEXCEPT {
+FMT_CONSTEXPR text_style bg(detail::color_type background) FMT_NOEXCEPT {
   return text_style(/*is_foreground=*/false, background);
 }
 
@@ -350,21 +350,21 @@
   return text_style(lhs) | rhs;
 }
 
-namespace internal {
+namespace detail {
 
 template <typename Char> struct ansi_color_escape {
-  FMT_CONSTEXPR ansi_color_escape(internal::color_type text_color,
+  FMT_CONSTEXPR ansi_color_escape(detail::color_type text_color,
                                   const char* esc) FMT_NOEXCEPT {
     // If we have a terminal color, we need to output another escape code
     // sequence.
     if (!text_color.is_rgb) {
-      bool is_background = esc == internal::data::background_color;
+      bool is_background = esc == detail::data::background_color;
       uint32_t value = text_color.value.term_color;
       // Background ASCII codes are the same as the foreground ones but with
       // 10 more.
       if (is_background) value += 10u;
 
-      std::size_t index = 0;
+      size_t index = 0;
       buffer[index++] = static_cast<Char>('\x1b');
       buffer[index++] = static_cast<Char>('[');
 
@@ -398,7 +398,7 @@
     if (em_bits & static_cast<uint8_t>(emphasis::strikethrough))
       em_codes[3] = 9;
 
-    std::size_t index = 0;
+    size_t index = 0;
     for (int i = 0; i < 4; ++i) {
       if (!em_codes[i]) continue;
       buffer[index++] = static_cast<Char>('\x1b');
@@ -412,7 +412,7 @@
 
   FMT_CONSTEXPR const Char* begin() const FMT_NOEXCEPT { return buffer; }
   FMT_CONSTEXPR const Char* end() const FMT_NOEXCEPT {
-    return buffer + std::strlen(buffer);
+    return buffer + std::char_traits<Char>::length(buffer);
   }
 
  private:
@@ -429,14 +429,14 @@
 
 template <typename Char>
 FMT_CONSTEXPR ansi_color_escape<Char> make_foreground_color(
-    internal::color_type foreground) FMT_NOEXCEPT {
-  return ansi_color_escape<Char>(foreground, internal::data::foreground_color);
+    detail::color_type foreground) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(foreground, detail::data::foreground_color);
 }
 
 template <typename Char>
 FMT_CONSTEXPR ansi_color_escape<Char> make_background_color(
-    internal::color_type background) FMT_NOEXCEPT {
-  return ansi_color_escape<Char>(background, internal::data::background_color);
+    detail::color_type background) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(background, detail::data::background_color);
 }
 
 template <typename Char>
@@ -455,73 +455,71 @@
 }
 
 template <typename Char> inline void reset_color(FILE* stream) FMT_NOEXCEPT {
-  fputs(internal::data::reset_color, stream);
+  fputs(detail::data::reset_color, stream);
 }
 
 template <> inline void reset_color<wchar_t>(FILE* stream) FMT_NOEXCEPT {
-  fputs(internal::data::wreset_color, stream);
+  fputs(detail::data::wreset_color, stream);
 }
 
 template <typename Char>
-inline void reset_color(basic_memory_buffer<Char>& buffer) FMT_NOEXCEPT {
+inline void reset_color(buffer<Char>& buffer) FMT_NOEXCEPT {
   const char* begin = data::reset_color;
   const char* end = begin + sizeof(data::reset_color) - 1;
   buffer.append(begin, end);
 }
 
 template <typename Char>
-void vformat_to(basic_memory_buffer<Char>& buf, const text_style& ts,
+void vformat_to(buffer<Char>& buf, const text_style& ts,
                 basic_string_view<Char> format_str,
-                basic_format_args<buffer_context<Char>> args) {
+                basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   bool has_style = false;
   if (ts.has_emphasis()) {
     has_style = true;
-    auto emphasis = internal::make_emphasis<Char>(ts.get_emphasis());
+    auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
     buf.append(emphasis.begin(), emphasis.end());
   }
   if (ts.has_foreground()) {
     has_style = true;
-    auto foreground =
-        internal::make_foreground_color<Char>(ts.get_foreground());
+    auto foreground = detail::make_foreground_color<Char>(ts.get_foreground());
     buf.append(foreground.begin(), foreground.end());
   }
   if (ts.has_background()) {
     has_style = true;
-    auto background =
-        internal::make_background_color<Char>(ts.get_background());
+    auto background = detail::make_background_color<Char>(ts.get_background());
     buf.append(background.begin(), background.end());
   }
-  vformat_to(buf, format_str, args);
-  if (has_style) {
-    internal::reset_color<Char>(buf);
-  }
+  detail::vformat_to(buf, format_str, args);
+  if (has_style) detail::reset_color<Char>(buf);
 }
-}  // namespace internal
+}  // namespace detail
 
 template <typename S, typename Char = char_t<S>>
 void vprint(std::FILE* f, const text_style& ts, const S& format,
-            basic_format_args<buffer_context<Char>> args) {
+            basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buf;
-  internal::vformat_to(buf, ts, to_string_view(format), args);
+  detail::vformat_to(buf, ts, to_string_view(format), args);
   buf.push_back(Char(0));
-  internal::fputs(buf.data(), f);
+  detail::fputs(buf.data(), f);
 }
 
 /**
+  \rst
   Formats a string and prints it to the specified file stream using ANSI
   escape sequences to specify text formatting.
-  Example:
+
+  **Example**::
+
     fmt::print(fmt::emphasis::bold | fg(fmt::color::red),
                "Elapsed time: {0:.2f} seconds", 1.23);
+  \endrst
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 void print(std::FILE* f, const text_style& ts, const S& format_str,
            const Args&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = buffer_context<char_t<S>>;
-  format_arg_store<context, Args...> as{args...};
-  vprint(f, ts, format_str, basic_format_args<context>(as));
+  vprint(f, ts, format_str,
+         fmt::make_args_checked<Args...>(format_str, args...));
 }
 
 /**
@@ -532,7 +530,7 @@
                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 void print(const text_style& ts, const S& format_str, const Args&... args) {
   return print(stdout, ts, format_str, args...);
 }
@@ -540,9 +538,9 @@
 template <typename S, typename Char = char_t<S>>
 inline std::basic_string<Char> vformat(
     const text_style& ts, const S& format_str,
-    basic_format_args<buffer_context<Char>> args) {
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buf;
-  internal::vformat_to(buf, ts, to_string_view(format_str), args);
+  detail::vformat_to(buf, ts, to_string_view(format_str), args);
   return fmt::to_string(buf);
 }
 
@@ -562,7 +560,42 @@
 inline std::basic_string<Char> format(const text_style& ts, const S& format_str,
                                       const Args&... args) {
   return vformat(ts, to_string_view(format_str),
-                 {internal::make_args_checked<Args...>(format_str, args...)});
+                 fmt::make_args_checked<Args...>(format_str, args...));
+}
+
+/**
+  Formats a string with the given text_style and writes the output to ``out``.
+ */
+template <typename OutputIt, typename Char,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
+OutputIt vformat_to(
+    OutputIt out, const text_style& ts, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  decltype(detail::get_buffer<Char>(out)) buf(detail::get_buffer_init(out));
+  detail::vformat_to(buf, ts, format_str, args);
+  return detail::get_iterator(buf);
+}
+
+/**
+  \rst
+  Formats arguments with the given text_style, writes the result to the output
+  iterator ``out`` and returns the iterator past the end of the output range.
+
+  **Example**::
+
+    std::vector<char> out;
+    fmt::format_to(std::back_inserter(out),
+                   fmt::emphasis::bold | fg(fmt::color::red), "{}", 42);
+  \endrst
+*/
+template <typename OutputIt, typename S, typename... Args,
+          bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value&&
+              detail::is_string<S>::value>
+inline auto format_to(OutputIt out, const text_style& ts, const S& format_str,
+                      Args&&... args) ->
+    typename std::enable_if<enable, OutputIt>::type {
+  return vformat_to(out, ts, to_string_view(format_str),
+                    fmt::make_args_checked<Args...>(format_str, args...));
 }
 
 FMT_END_NAMESPACE
diff --git a/include/fmt/compile.h b/include/fmt/compile.h
index f65f5a7..3a33b02 100644
--- a/include/fmt/compile.h
+++ b/include/fmt/compile.h
@@ -9,10 +9,37 @@
 #define FMT_COMPILE_H_
 
 #include <vector>
+
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
+
+// A compile-time string which is compiled into fast formatting code.
+class compiled_string {};
+
+template <typename S>
+struct is_compiled_string : std::is_base_of<compiled_string, S> {};
+
+/**
+  \rst
+  Converts a string literal *s* into a format string that will be parsed at
+  compile time and converted into efficient formatting code. Requires C++17
+  ``constexpr if`` compiler support.
+
+  **Example**::
+
+    // Converts 42 into std::string using the most efficient method and no
+    // runtime format string processing.
+    std::string s = fmt::format(FMT_COMPILE("{}"), 42);
+  \endrst
+ */
+#define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::detail::compiled_string)
+
+template <typename T, typename... Tail>
+const T& first(const T& value, const Tail&...) {
+  return value;
+}
 
 // Part of a compiled format string. It can be either literal text or a
 // replacement field.
@@ -26,11 +53,11 @@
 
   kind part_kind;
   union value {
-    unsigned arg_index;
+    int arg_index;
     basic_string_view<Char> str;
     replacement repl;
 
-    FMT_CONSTEXPR value(unsigned index = 0) : arg_index(index) {}
+    FMT_CONSTEXPR value(int index = 0) : arg_index(index) {}
     FMT_CONSTEXPR value(basic_string_view<Char> s) : str(s) {}
     FMT_CONSTEXPR value(replacement r) : repl(r) {}
   } val;
@@ -40,7 +67,7 @@
   FMT_CONSTEXPR format_part(kind k = kind::arg_index, value v = {})
       : part_kind(k), val(v) {}
 
-  static FMT_CONSTEXPR format_part make_arg_index(unsigned index) {
+  static FMT_CONSTEXPR format_part make_arg_index(int index) {
     return format_part(kind::arg_index, index);
   }
   static FMT_CONSTEXPR format_part make_arg_name(basic_string_view<Char> name) {
@@ -61,13 +88,15 @@
     if (begin != end) ++num_parts;
   }
 
-  FMT_CONSTEXPR void on_arg_id() { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(unsigned) { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) { ++num_parts; }
+  FMT_CONSTEXPR int on_arg_id() { return ++num_parts, 0; }
+  FMT_CONSTEXPR int on_arg_id(int) { return ++num_parts, 0; }
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
+    return ++num_parts, 0;
+  }
 
-  FMT_CONSTEXPR void on_replacement_field(const Char*) {}
+  FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin,
+  FMT_CONSTEXPR const Char* on_format_specs(int, const Char* begin,
                                             const Char* end) {
     // Find the matching brace.
     unsigned brace_counter = 0;
@@ -115,25 +144,28 @@
       handler_(part::make_text({begin, to_unsigned(end - begin)}));
   }
 
-  FMT_CONSTEXPR void on_arg_id() {
+  FMT_CONSTEXPR int on_arg_id() {
     part_ = part::make_arg_index(parse_context_.next_arg_id());
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_arg_id(unsigned id) {
+  FMT_CONSTEXPR int on_arg_id(int id) {
     parse_context_.check_arg_id(id);
     part_ = part::make_arg_index(id);
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char> id) {
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char> id) {
     part_ = part::make_arg_name(id);
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_replacement_field(const Char* ptr) {
+  FMT_CONSTEXPR void on_replacement_field(int, const Char* ptr) {
     part_.arg_id_end = ptr;
     handler_(part_);
   }
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin,
+  FMT_CONSTEXPR const Char* on_format_specs(int, const Char* begin,
                                             const Char* end) {
     auto repl = typename part::replacement();
     dynamic_specs_handler<basic_format_parse_context<Char>> handler(
@@ -159,23 +191,24 @@
       format_string_compiler<Char, PartHandler>(format_str, handler));
 }
 
-template <typename Range, typename Context, typename Id>
+template <typename OutputIt, typename Context, typename Id>
 void format_arg(
-    basic_format_parse_context<typename Range::value_type>& parse_ctx,
+    basic_format_parse_context<typename Context::char_type>& parse_ctx,
     Context& ctx, Id arg_id) {
-  ctx.advance_to(
-      visit_format_arg(arg_formatter<Range>(ctx, &parse_ctx), ctx.arg(arg_id)));
+  ctx.advance_to(visit_format_arg(
+      arg_formatter<OutputIt, typename Context::char_type>(ctx, &parse_ctx),
+      ctx.arg(arg_id)));
 }
 
 // vformat_to is defined in a subnamespace to prevent ADL.
 namespace cf {
-template <typename Context, typename Range, typename CompiledFormat>
-auto vformat_to(Range out, CompiledFormat& cf, basic_format_args<Context> args)
-    -> typename Context::iterator {
+template <typename Context, typename OutputIt, typename CompiledFormat>
+auto vformat_to(OutputIt out, CompiledFormat& cf,
+                basic_format_args<Context> args) -> typename Context::iterator {
   using char_type = typename Context::char_type;
   basic_format_parse_context<char_type> parse_ctx(
       to_string_view(cf.format_str_));
-  Context ctx(out.begin(), args);
+  Context ctx(out, args);
 
   const auto& parts = cf.parts();
   for (auto part_it = std::begin(parts); part_it != std::end(parts);
@@ -196,12 +229,12 @@
 
     case format_part_t::kind::arg_index:
       advance_to(parse_ctx, part.arg_id_end);
-      internal::format_arg<Range>(parse_ctx, ctx, value.arg_index);
+      detail::format_arg<OutputIt>(parse_ctx, ctx, value.arg_index);
       break;
 
     case format_part_t::kind::arg_name:
       advance_to(parse_ctx, part.arg_id_end);
-      internal::format_arg<Range>(parse_ctx, ctx, value.str);
+      detail::format_arg<OutputIt>(parse_ctx, ctx, value.str);
       break;
 
     case format_part_t::kind::replacement: {
@@ -225,7 +258,9 @@
 
       advance_to(parse_ctx, part.arg_id_end);
       ctx.advance_to(
-          visit_format_arg(arg_formatter<Range>(ctx, nullptr, &specs), arg));
+          visit_format_arg(arg_formatter<OutputIt, typename Context::char_type>(
+                               ctx, nullptr, &specs),
+                           arg));
       break;
     }
     }
@@ -239,7 +274,7 @@
 template <typename S, typename = void>
 struct compiled_format_base : basic_compiled_format {
   using char_type = char_t<S>;
-  using parts_container = std::vector<internal::format_part<char_type>>;
+  using parts_container = std::vector<detail::format_part<char_type>>;
 
   parts_container compiled_parts;
 
@@ -304,7 +339,7 @@
   const parts_container& parts() const {
     static FMT_CONSTEXPR_DECL const auto compiled_parts =
         compile_to_parts<char_type, num_format_parts>(
-            internal::to_string_view(S()));
+            detail::to_string_view(S()));
     return compiled_parts.data;
   }
 };
@@ -317,8 +352,8 @@
  private:
   basic_string_view<char_type> format_str_;
 
-  template <typename Context, typename Range, typename CompiledFormat>
-  friend auto cf::vformat_to(Range out, CompiledFormat& cf,
+  template <typename Context, typename OutputIt, typename CompiledFormat>
+  friend auto cf::vformat_to(OutputIt out, CompiledFormat& cf,
                              basic_format_args<Context> args) ->
       typename Context::iterator;
 
@@ -333,7 +368,8 @@
 
 // Returns a reference to the argument at index N from [first, rest...].
 template <int N, typename T, typename... Args>
-constexpr const auto& get(const T& first, const Args&... rest) {
+constexpr const auto& get([[maybe_unused]] const T& first,
+                          [[maybe_unused]] const Args&... rest) {
   static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
   if constexpr (N == 0)
     return first;
@@ -350,49 +386,39 @@
 template <int N, typename T>
 using get_type = typename get_type_impl<N, T>::type;
 
+template <typename T> struct is_compiled_format : std::false_type {};
+
 template <typename Char> struct text {
   basic_string_view<Char> data;
   using char_type = Char;
 
   template <typename OutputIt, typename... Args>
   OutputIt format(OutputIt out, const Args&...) const {
-    // TODO: reserve
-    return copy_str<Char>(data.begin(), data.end(), out);
+    return write<Char>(out, data);
   }
 };
 
 template <typename Char>
+struct is_compiled_format<text<Char>> : std::true_type {};
+
+template <typename Char>
 constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
                                size_t size) {
   return {{&s[pos], size}};
 }
 
-template <typename Char, typename OutputIt, typename T,
-          std::enable_if_t<std::is_integral_v<T>, int> = 0>
-OutputIt format_default(OutputIt out, T value) {
-  // TODO: reserve
-  format_int fi(value);
-  return std::copy(fi.data(), fi.data() + fi.size(), out);
-}
+template <typename Char> struct code_unit {
+  Char value;
+  using char_type = Char;
 
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, double value) {
-  writer w(out);
-  w.write(value);
-  return w.out();
-}
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&...) const {
+    return write<Char>(out, value);
+  }
+};
 
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, Char value) {
-  *out++ = value;
-  return out;
-}
-
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, const Char* value) {
-  auto length = std::char_traits<Char>::length(value);
-  return copy_str<Char>(value, value + length, out);
-}
+template <typename Char>
+struct is_compiled_format<code_unit<Char>> : std::true_type {};
 
 // A replacement field that refers to argument N.
 template <typename Char, typename T, int N> struct field {
@@ -402,10 +428,32 @@
   OutputIt format(OutputIt out, const Args&... args) const {
     // This ensures that the argument type is convertile to `const T&`.
     const T& arg = get<N>(args...);
-    return format_default<Char>(out, arg);
+    return write<Char>(out, arg);
   }
 };
 
+template <typename Char, typename T, int N>
+struct is_compiled_format<field<Char, T, N>> : std::true_type {};
+
+// A replacement field that refers to argument N and has format specifiers.
+template <typename Char, typename T, int N> struct spec_field {
+  using char_type = Char;
+  mutable formatter<T, Char> fmt;
+
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&... args) const {
+    // This ensures that the argument type is convertile to `const T&`.
+    const T& arg = get<N>(args...);
+    const auto& vargs =
+        make_format_args<basic_format_context<OutputIt, Char>>(args...);
+    basic_format_context<OutputIt, Char> ctx(out, vargs);
+    return fmt.format(arg, ctx);
+  }
+};
+
+template <typename Char, typename T, int N>
+struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};
+
 template <typename L, typename R> struct concat {
   L lhs;
   R rhs;
@@ -419,6 +467,9 @@
 };
 
 template <typename L, typename R>
+struct is_compiled_format<concat<L, R>> : std::true_type {};
+
+template <typename L, typename R>
 constexpr concat<L, R> make_concat(L lhs, R rhs) {
   return {lhs, rhs};
 }
@@ -438,7 +489,8 @@
 
 template <typename Args, size_t POS, int ID, typename T, typename S>
 constexpr auto parse_tail(T head, S format_str) {
-  if constexpr (POS != to_string_view(format_str).size()) {
+  if constexpr (POS !=
+                basic_string_view<typename S::char_type>(format_str).size()) {
     constexpr auto tail = compile_format_string<Args, POS, ID>(format_str);
     if constexpr (std::is_same<remove_cvref_t<decltype(tail)>,
                                unknown_format>())
@@ -450,6 +502,22 @@
   }
 }
 
+template <typename T, typename Char> struct parse_specs_result {
+  formatter<T, Char> fmt;
+  size_t end;
+  int next_arg_id;
+};
+
+template <typename T, typename Char>
+constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
+                                                  size_t pos, int arg_id) {
+  str.remove_prefix(pos);
+  auto ctx = basic_format_parse_context<Char>(str, {}, arg_id + 1);
+  auto f = formatter<T, Char>();
+  auto end = f.parse(ctx);
+  return {f, pos + (end - str.data()) + 1, ctx.next_arg_id()};
+}
+
 // Compiles a non-empty format string and returns the compiled representation
 // or unknown_format() on unrecognized input.
 template <typename Args, size_t POS, int ID, typename S>
@@ -463,12 +531,13 @@
       return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
     } else if constexpr (str[POS + 1] == '}') {
       using type = get_type<ID, Args>;
-      if constexpr (std::is_same<type, int>::value) {
-        return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
-                                                 format_str);
-      } else {
-        return unknown_format();
-      }
+      return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
+                                               format_str);
+    } else if constexpr (str[POS + 1] == ':') {
+      using type = get_type<ID, Args>;
+      constexpr auto result = parse_specs<type>(str, POS + 2, ID);
+      return parse_tail<Args, result.end, result.next_arg_id>(
+          spec_field<char_type, type, ID>{result.fmt}, format_str);
     } else {
       return unknown_format();
     }
@@ -478,108 +547,153 @@
     return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
   } else {
     constexpr auto end = parse_text(str, POS + 1);
-    return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
-                                     format_str);
+    if constexpr (end - POS > 1) {
+      return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
+                                       format_str);
+    } else {
+      return parse_tail<Args, end, ID>(code_unit<char_type>{str[POS]},
+                                       format_str);
+    }
   }
 }
-#endif  // __cpp_if_constexpr
-}  // namespace internal
 
-#if FMT_USE_CONSTEXPR
-#  ifdef __cpp_if_constexpr
 template <typename... Args, typename S,
-          FMT_ENABLE_IF(is_compile_string<S>::value)>
+          FMT_ENABLE_IF(is_compile_string<S>::value ||
+                        detail::is_compiled_string<S>::value)>
 constexpr auto compile(S format_str) {
   constexpr basic_string_view<typename S::char_type> str = format_str;
   if constexpr (str.size() == 0) {
-    return internal::make_text(str, 0, 0);
+    return detail::make_text(str, 0, 0);
   } else {
     constexpr auto result =
-        internal::compile_format_string<internal::type_list<Args...>, 0, 0>(
+        detail::compile_format_string<detail::type_list<Args...>, 0, 0>(
             format_str);
     if constexpr (std::is_same<remove_cvref_t<decltype(result)>,
-                               internal::unknown_format>()) {
-      return internal::compiled_format<S, Args...>(to_string_view(format_str));
+                               detail::unknown_format>()) {
+      return detail::compiled_format<S, Args...>(to_string_view(format_str));
     } else {
       return result;
     }
   }
 }
-
-template <typename CompiledFormat, typename... Args,
-          typename Char = typename CompiledFormat::char_type,
-          FMT_ENABLE_IF(!std::is_base_of<internal::basic_compiled_format,
-                                         CompiledFormat>::value)>
-std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
-  basic_memory_buffer<Char> buffer;
-  using range = buffer_range<Char>;
-  using context = buffer_context<Char>;
-  cf.format(std::back_inserter(buffer), args...);
-  return to_string(buffer);
-}
-
-template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(!std::is_base_of<internal::basic_compiled_format,
-                                         CompiledFormat>::value)>
-OutputIt format_to(OutputIt out, const CompiledFormat& cf,
-                   const Args&... args) {
-  return cf.format(out, args...);
-}
-#  else
+#else
 template <typename... Args, typename S,
           FMT_ENABLE_IF(is_compile_string<S>::value)>
-constexpr auto compile(S format_str) -> internal::compiled_format<S, Args...> {
-  return internal::compiled_format<S, Args...>(to_string_view(format_str));
+constexpr auto compile(S format_str) -> detail::compiled_format<S, Args...> {
+  return detail::compiled_format<S, Args...>(to_string_view(format_str));
 }
-#  endif  // __cpp_if_constexpr
-#endif    // FMT_USE_CONSTEXPR
+#endif  // __cpp_if_constexpr
 
 // Compiles the format string which must be a string literal.
 template <typename... Args, typename Char, size_t N>
 auto compile(const Char (&format_str)[N])
-    -> internal::compiled_format<const Char*, Args...> {
-  return internal::compiled_format<const Char*, Args...>(
+    -> detail::compiled_format<const Char*, Args...> {
+  return detail::compiled_format<const Char*, Args...>(
       basic_string_view<Char>(format_str, N - 1));
 }
+}  // namespace detail
+
+// DEPRECATED! use FMT_COMPILE instead.
+template <typename... Args>
+FMT_DEPRECATED auto compile(const Args&... args)
+    -> decltype(detail::compile(args...)) {
+  return detail::compile(args...);
+}
+
+#if FMT_USE_CONSTEXPR
+#  ifdef __cpp_if_constexpr
 
 template <typename CompiledFormat, typename... Args,
           typename Char = typename CompiledFormat::char_type,
-          FMT_ENABLE_IF(std::is_base_of<internal::basic_compiled_format,
-                                        CompiledFormat>::value)>
-std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
+                                          const Args&... args) {
   basic_memory_buffer<Char> buffer;
-  using range = buffer_range<Char>;
-  using context = buffer_context<Char>;
-  internal::cf::vformat_to<context>(range(buffer), cf,
-                                    {make_format_args<context>(args...)});
+  cf.format(detail::buffer_appender<Char>(buffer), args...);
   return to_string(buffer);
 }
 
 template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(std::is_base_of<internal::basic_compiled_format,
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+OutputIt format_to(OutputIt out, const CompiledFormat& cf,
+                   const Args&... args) {
+  return cf.format(out, args...);
+}
+#  endif  // __cpp_if_constexpr
+#endif    // FMT_USE_CONSTEXPR
+
+template <typename CompiledFormat, typename... Args,
+          typename Char = typename CompiledFormat::char_type,
+          FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
+                                        CompiledFormat>::value)>
+std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
+  basic_memory_buffer<Char> buffer;
+  using context = buffer_context<Char>;
+  detail::cf::vformat_to<context>(detail::buffer_appender<Char>(buffer), cf,
+                                  make_format_args<context>(args...));
+  return to_string(buffer);
+}
+
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
+                                                           Args&&... args) {
+#ifdef __cpp_if_constexpr
+  if constexpr (std::is_same<typename S::char_type, char>::value) {
+    constexpr basic_string_view<typename S::char_type> str = S();
+    if (str.size() == 2 && str[0] == '{' && str[1] == '}')
+      return fmt::to_string(detail::first(args...));
+  }
+#endif
+  constexpr auto compiled = detail::compile<Args...>(S());
+  return format(compiled, std::forward<Args>(args)...);
+}
+
+template <typename OutputIt, typename CompiledFormat, typename... Args,
+          FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
                                         CompiledFormat>::value)>
 OutputIt format_to(OutputIt out, const CompiledFormat& cf,
                    const Args&... args) {
   using char_type = typename CompiledFormat::char_type;
-  using range = internal::output_range<OutputIt, char_type>;
   using context = format_context_t<OutputIt, char_type>;
-  return internal::cf::vformat_to<context>(
-      range(out), cf, {make_format_args<context>(args...)});
+  return detail::cf::vformat_to<context>(out, cf,
+                                         make_format_args<context>(args...));
 }
 
-template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value)>
-format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
-                                         const CompiledFormat& cf,
-                                         const Args&... args) {
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+OutputIt format_to(OutputIt out, const S&, const Args&... args) {
+  constexpr auto compiled = detail::compile<Args...>(S());
+  return format_to(out, compiled, args...);
+}
+
+template <typename OutputIt, typename CompiledFormat, typename... Args>
+auto format_to_n(OutputIt out, size_t n, const CompiledFormat& cf,
+                 const Args&... args) ->
+    typename std::enable_if<
+        detail::is_output_iterator<OutputIt,
+                                   typename CompiledFormat::char_type>::value &&
+            std::is_base_of<detail::basic_compiled_format,
+                            CompiledFormat>::value,
+        format_to_n_result<OutputIt>>::type {
   auto it =
-      format_to(internal::truncating_iterator<OutputIt>(out, n), cf, args...);
+      format_to(detail::truncating_iterator<OutputIt>(out, n), cf, args...);
+  return {it.base(), it.count()};
+}
+
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n, const S&,
+                                         const Args&... args) {
+  constexpr auto compiled = detail::compile<Args...>(S());
+  auto it = format_to(detail::truncating_iterator<OutputIt>(out, n), compiled,
+                      args...);
   return {it.base(), it.count()};
 }
 
 template <typename CompiledFormat, typename... Args>
-std::size_t formatted_size(const CompiledFormat& cf, const Args&... args) {
-  return format_to(internal::counting_iterator(), cf, args...).count();
+size_t formatted_size(const CompiledFormat& cf, const Args&... args) {
+  return format_to(detail::counting_iterator(), cf, args...).count();
 }
 
 FMT_END_NAMESPACE
diff --git a/include/fmt/core.h b/include/fmt/core.h
index 13d74ba..0a81e0c 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -10,30 +10,20 @@
 
 #include <cstdio>  // std::FILE
 #include <cstring>
+#include <functional>
 #include <iterator>
+#include <memory>
 #include <string>
 #include <type_traits>
+#include <vector>
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 60101
+#define FMT_VERSION 70103
 
-#ifdef __has_feature
-#  define FMT_HAS_FEATURE(x) __has_feature(x)
+#ifdef __clang__
+#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
 #else
-#  define FMT_HAS_FEATURE(x) 0
-#endif
-
-#if defined(__has_include) && !defined(__INTELLISENSE__) && \
-    !(defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1600)
-#  define FMT_HAS_INCLUDE(x) __has_include(x)
-#else
-#  define FMT_HAS_INCLUDE(x) 0
-#endif
-
-#ifdef __has_cpp_attribute
-#  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
-#else
-#  define FMT_HAS_CPP_ATTRIBUTE(x) 0
+#  define FMT_CLANG_VERSION 0
 #endif
 
 #if defined(__GNUC__) && !defined(__clang__)
@@ -42,6 +32,12 @@
 #  define FMT_GCC_VERSION 0
 #endif
 
+#if defined(__INTEL_COMPILER)
+#  define FMT_ICC_VERSION __INTEL_COMPILER
+#else
+#  define FMT_ICC_VERSION 0
+#endif
+
 #if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
 #  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
 #else
@@ -56,17 +52,44 @@
 
 #ifdef _MSC_VER
 #  define FMT_MSC_VER _MSC_VER
+#  define FMT_SUPPRESS_MSC_WARNING(n) __pragma(warning(suppress : n))
 #else
 #  define FMT_MSC_VER 0
+#  define FMT_SUPPRESS_MSC_WARNING(n)
 #endif
 
+#ifdef __has_feature
+#  define FMT_HAS_FEATURE(x) __has_feature(x)
+#else
+#  define FMT_HAS_FEATURE(x) 0
+#endif
+
+#if defined(__has_include) && !defined(__INTELLISENSE__) && \
+    (!FMT_ICC_VERSION || FMT_ICC_VERSION >= 1600)
+#  define FMT_HAS_INCLUDE(x) __has_include(x)
+#else
+#  define FMT_HAS_INCLUDE(x) 0
+#endif
+
+#ifdef __has_cpp_attribute
+#  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
+#else
+#  define FMT_HAS_CPP_ATTRIBUTE(x) 0
+#endif
+
+#define FMT_HAS_CPP14_ATTRIBUTE(attribute) \
+  (__cplusplus >= 201402L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+
+#define FMT_HAS_CPP17_ATTRIBUTE(attribute) \
+  (__cplusplus >= 201703L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+
 // Check if relaxed C++14 constexpr is supported.
 // GCC doesn't allow throw in constexpr until version 6 (bug 67371).
 #ifndef FMT_USE_CONSTEXPR
 #  define FMT_USE_CONSTEXPR                                           \
     (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
      (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
-        !FMT_NVCC
+        !FMT_NVCC && !FMT_ICC_VERSION
 #endif
 #if FMT_USE_CONSTEXPR
 #  define FMT_CONSTEXPR constexpr
@@ -77,7 +100,7 @@
 #endif
 
 #ifndef FMT_OVERRIDE
-#  if FMT_HAS_FEATURE(cxx_override) || \
+#  if FMT_HAS_FEATURE(cxx_override_control) || \
       (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
 #    define FMT_OVERRIDE override
 #  else
@@ -117,19 +140,20 @@
 #  endif
 #endif
 
-// [[noreturn]] is disabled on MSVC because of bogus unreachable code warnings.
-#if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VER
+// [[noreturn]] is disabled on MSVC and NVCC because of bogus unreachable code
+// warnings.
+#if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VER && \
+    !FMT_NVCC
 #  define FMT_NORETURN [[noreturn]]
 #else
 #  define FMT_NORETURN
 #endif
 
 #ifndef FMT_DEPRECATED
-#  if (FMT_HAS_CPP_ATTRIBUTE(deprecated) && __cplusplus >= 201402L) || \
-      FMT_MSC_VER >= 1900
+#  if FMT_HAS_CPP14_ATTRIBUTE(deprecated) || FMT_MSC_VER >= 1900
 #    define FMT_DEPRECATED [[deprecated]]
 #  else
-#    if defined(__GNUC__) || defined(__clang__)
+#    if (defined(__GNUC__) && !defined(__LCC__)) || defined(__clang__)
 #      define FMT_DEPRECATED __attribute__((deprecated))
 #    elif FMT_MSC_VER
 #      define FMT_DEPRECATED __declspec(deprecated)
@@ -139,16 +163,32 @@
 #  endif
 #endif
 
-// Workaround broken [[deprecated]] in the Intel compiler and NVCC.
-#if defined(__INTEL_COMPILER) || FMT_NVCC
+// Workaround broken [[deprecated]] in the Intel, PGI and NVCC compilers.
+#if FMT_ICC_VERSION || defined(__PGI) || FMT_NVCC
 #  define FMT_DEPRECATED_ALIAS
 #else
 #  define FMT_DEPRECATED_ALIAS FMT_DEPRECATED
 #endif
 
-#ifndef FMT_BEGIN_NAMESPACE
+#ifndef FMT_INLINE
+#  if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#    define FMT_INLINE inline __attribute__((always_inline))
+#  else
+#    define FMT_INLINE inline
+#  endif
+#endif
+
+#ifndef FMT_USE_INLINE_NAMESPACES
 #  if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
-      FMT_MSC_VER >= 1900
+      (FMT_MSC_VER >= 1900 && !_MANAGED)
+#    define FMT_USE_INLINE_NAMESPACES 1
+#  else
+#    define FMT_USE_INLINE_NAMESPACES 0
+#  endif
+#endif
+
+#ifndef FMT_BEGIN_NAMESPACE
+#  if FMT_USE_INLINE_NAMESPACES
 #    define FMT_INLINE_NAMESPACE inline namespace
 #    define FMT_END_NAMESPACE \
       }                       \
@@ -157,21 +197,26 @@
 #    define FMT_INLINE_NAMESPACE namespace
 #    define FMT_END_NAMESPACE \
       }                       \
-      using namespace v6;     \
+      using namespace v7;     \
       }
 #  endif
 #  define FMT_BEGIN_NAMESPACE \
     namespace fmt {           \
-    FMT_INLINE_NAMESPACE v6 {
+    FMT_INLINE_NAMESPACE v7 {
 #endif
 
 #if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
+#  define FMT_CLASS_API FMT_SUPPRESS_MSC_WARNING(4275)
 #  ifdef FMT_EXPORT
 #    define FMT_API __declspec(dllexport)
+#    define FMT_EXTERN_TEMPLATE_API FMT_API
+#    define FMT_EXPORTED
 #  elif defined(FMT_SHARED)
 #    define FMT_API __declspec(dllimport)
 #    define FMT_EXTERN_TEMPLATE_API FMT_API
 #  endif
+#else
+#  define FMT_CLASS_API
 #endif
 #ifndef FMT_API
 #  define FMT_API
@@ -179,6 +224,9 @@
 #ifndef FMT_EXTERN_TEMPLATE_API
 #  define FMT_EXTERN_TEMPLATE_API
 #endif
+#ifndef FMT_INSTANTIATION_DEF_API
+#  define FMT_INSTANTIATION_DEF_API FMT_API
+#endif
 
 #ifndef FMT_HEADER_ONLY
 #  define FMT_EXTERN extern
@@ -197,9 +245,16 @@
 #  define FMT_USE_EXPERIMENTAL_STRING_VIEW
 #endif
 
+#ifndef FMT_UNICODE
+#  define FMT_UNICODE !FMT_MSC_VER
+#endif
+#if FMT_UNICODE && FMT_MSC_VER
+#  pragma execution_character_set("utf-8")
+#endif
+
 FMT_BEGIN_NAMESPACE
 
-// Implementations of enable_if_t and other types for pre-C++14 systems.
+// Implementations of enable_if_t and other metafunctions for older systems.
 template <bool B, class T = void>
 using enable_if_t = typename std::enable_if<B, T>::type;
 template <bool B, class T, class F>
@@ -211,6 +266,8 @@
 using remove_const_t = typename std::remove_const<T>::type;
 template <typename T>
 using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
+template <typename T> struct type_identity { using type = T; };
+template <typename T> using type_identity_t = typename type_identity<T>::type;
 
 struct monostate {};
 
@@ -219,21 +276,23 @@
 // to workaround a bug in MSVC 2019 (see #1140 and #1186).
 #define FMT_ENABLE_IF(...) enable_if_t<(__VA_ARGS__), int> = 0
 
-namespace internal {
+namespace detail {
 
-// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
-template <typename... Ts> struct void_t_impl { using type = void; };
+// A helper function to suppress "conditional expression is constant" warnings.
+template <typename T> constexpr T const_check(T value) { return value; }
 
-FMT_API void assert_fail(const char* file, int line, const char* message);
+FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
+                                      const char* message);
 
 #ifndef FMT_ASSERT
 #  ifdef NDEBUG
-#    define FMT_ASSERT(condition, message)
+// FMT_ASSERT is not empty to avoid -Werror=empty-body.
+#    define FMT_ASSERT(condition, message) ((void)0)
 #  else
-#    define FMT_ASSERT(condition, message) \
-      ((condition)                         \
-           ? void()                        \
-           : fmt::internal::assert_fail(__FILE__, __LINE__, (message)))
+#    define FMT_ASSERT(condition, message)                                    \
+      ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
+           ? (void)0                                                          \
+           : ::fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
 #  endif
 #endif
 
@@ -248,7 +307,8 @@
 
 #ifdef FMT_USE_INT128
 // Do nothing.
-#elif defined(__SIZEOF_INT128__)
+#elif defined(__SIZEOF_INT128__) && !FMT_NVCC && \
+    !(FMT_CLANG_VERSION && FMT_MSC_VER)
 #  define FMT_USE_INT128 1
 using int128_t = __int128_t;
 using uint128_t = __uint128_t;
@@ -266,10 +326,24 @@
   FMT_ASSERT(value >= 0, "negative value");
   return static_cast<typename std::make_unsigned<Int>::type>(value);
 }
-}  // namespace internal
 
-template <typename... Ts>
-using void_t = typename internal::void_t_impl<Ts...>::type;
+FMT_SUPPRESS_MSC_WARNING(4566) constexpr unsigned char micro[] = "\u00B5";
+
+template <typename Char> constexpr bool is_unicode() {
+  return FMT_UNICODE || sizeof(Char) != 1 ||
+         (sizeof(micro) == 3 && micro[0] == 0xC2 && micro[1] == 0xB5);
+}
+
+#ifdef __cpp_char8_t
+using char8_type = char8_t;
+#else
+enum char8_type : unsigned char {};
+#endif
+}  // namespace detail
+
+#ifdef FMT_USE_INTERNAL
+namespace internal = detail;  // DEPRECATED
+#endif
 
 /**
   An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
@@ -284,13 +358,13 @@
   size_t size_;
 
  public:
-  using char_type = Char;
+  using value_type = Char;
   using iterator = const Char*;
 
-  FMT_CONSTEXPR basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
+  constexpr basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
 
   /** Constructs a string reference object from a C string and a size. */
-  FMT_CONSTEXPR basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
+  constexpr basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
       : data_(s),
         size_(count) {}
 
@@ -300,6 +374,9 @@
     the size with ``std::char_traits<Char>::length``.
     \endrst
    */
+#if __cplusplus >= 201703L  // C++17's char_traits::length() is constexpr.
+  FMT_CONSTEXPR
+#endif
   basic_string_view(const Char* s)
       : data_(s), size_(std::char_traits<Char>::length(s)) {}
 
@@ -310,22 +387,21 @@
       : data_(s.data()),
         size_(s.size()) {}
 
-  template <
-      typename S,
-      FMT_ENABLE_IF(std::is_same<S, internal::std_string_view<Char>>::value)>
+  template <typename S, FMT_ENABLE_IF(std::is_same<
+                                      S, detail::std_string_view<Char>>::value)>
   FMT_CONSTEXPR basic_string_view(S s) FMT_NOEXCEPT : data_(s.data()),
                                                       size_(s.size()) {}
 
   /** Returns a pointer to the string data. */
-  FMT_CONSTEXPR const Char* data() const { return data_; }
+  constexpr const Char* data() const { return data_; }
 
   /** Returns the string size. */
-  FMT_CONSTEXPR size_t size() const { return size_; }
+  constexpr size_t size() const { return size_; }
 
-  FMT_CONSTEXPR iterator begin() const { return data_; }
-  FMT_CONSTEXPR iterator end() const { return data_ + size_; }
+  constexpr iterator begin() const { return data_; }
+  constexpr iterator end() const { return data_ + size_; }
 
-  FMT_CONSTEXPR const Char& operator[](size_t pos) const { return data_[pos]; }
+  constexpr const Char& operator[](size_t pos) const { return data_[pos]; }
 
   FMT_CONSTEXPR void remove_prefix(size_t n) {
     data_ += n;
@@ -364,16 +440,11 @@
 using string_view = basic_string_view<char>;
 using wstring_view = basic_string_view<wchar_t>;
 
-#ifndef __cpp_char8_t
-// A UTF-8 code unit type.
-enum char8_t : unsigned char {};
-#endif
-
 /** Specifies if ``T`` is a character type. Can be specialized by users. */
 template <typename T> struct is_char : std::false_type {};
 template <> struct is_char<char> : std::true_type {};
 template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<char8_t> : std::true_type {};
+template <> struct is_char<detail::char8_type> : std::true_type {};
 template <> struct is_char<char16_t> : std::true_type {};
 template <> struct is_char<char32_t> : std::true_type {};
 
@@ -410,14 +481,13 @@
 }
 
 template <typename Char,
-          FMT_ENABLE_IF(!std::is_empty<internal::std_string_view<Char>>::value)>
-inline basic_string_view<Char> to_string_view(
-    internal::std_string_view<Char> s) {
+          FMT_ENABLE_IF(!std::is_empty<detail::std_string_view<Char>>::value)>
+inline basic_string_view<Char> to_string_view(detail::std_string_view<Char> s) {
   return s;
 }
 
 // A base class for compile-time strings. It is defined in the fmt namespace to
-// make formatting functions visible via ADL, e.g. format(fmt("{}"), 42).
+// make formatting functions visible via ADL, e.g. format(FMT_STRING("{}"), 42).
 struct compile_string {};
 
 template <typename S>
@@ -428,9 +498,9 @@
   return s;
 }
 
-namespace internal {
+namespace detail {
 void to_string_view(...);
-using fmt::v6::to_string_view;
+using fmt::v7::to_string_view;
 
 // Specifies whether S is a string type convertible to fmt::basic_string_view.
 // It should be a constexpr function but MSVC 2017 fails to compile it in
@@ -442,20 +512,32 @@
 template <typename S, typename = void> struct char_t_impl {};
 template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
   using result = decltype(to_string_view(std::declval<S>()));
-  using type = typename result::char_type;
+  using type = typename result::value_type;
 };
 
+// Reports a compile-time error if S is not a valid format string.
+template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
+FMT_INLINE void check_format_string(const S&) {
+#ifdef FMT_ENFORCE_COMPILE_STRING
+  static_assert(is_compile_string<S>::value,
+                "FMT_ENFORCE_COMPILE_STRING requires all format strings to use "
+                "FMT_STRING.");
+#endif
+}
+template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
+void check_format_string(S);
+
 struct error_handler {
-  FMT_CONSTEXPR error_handler() = default;
-  FMT_CONSTEXPR error_handler(const error_handler&) = default;
+  constexpr error_handler() = default;
+  constexpr error_handler(const error_handler&) = default;
 
   // This function is intentionally not constexpr to give a compile-time error.
   FMT_NORETURN FMT_API void on_error(const char* message);
 };
-}  // namespace internal
+}  // namespace detail
 
 /** String's character type. */
-template <typename S> using char_t = typename internal::char_t_impl<S>::type;
+template <typename S> using char_t = typename detail::char_t_impl<S>::type;
 
 /**
   \rst
@@ -473,7 +555,7 @@
   +-----------------------+-------------------------------------+
   \endrst
  */
-template <typename Char, typename ErrorHandler = internal::error_handler>
+template <typename Char, typename ErrorHandler = detail::error_handler>
 class basic_format_parse_context : private ErrorHandler {
  private:
   basic_string_view<Char> format_str_;
@@ -483,26 +565,25 @@
   using char_type = Char;
   using iterator = typename basic_string_view<Char>::iterator;
 
-  explicit FMT_CONSTEXPR basic_format_parse_context(
-      basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
-      : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
+  explicit constexpr basic_format_parse_context(
+      basic_string_view<Char> format_str, ErrorHandler eh = {},
+      int next_arg_id = 0)
+      : ErrorHandler(eh), format_str_(format_str), next_arg_id_(next_arg_id) {}
 
   /**
     Returns an iterator to the beginning of the format string range being
     parsed.
    */
-  FMT_CONSTEXPR iterator begin() const FMT_NOEXCEPT {
-    return format_str_.begin();
-  }
+  constexpr iterator begin() const FMT_NOEXCEPT { return format_str_.begin(); }
 
   /**
     Returns an iterator past the end of the format string range being parsed.
    */
-  FMT_CONSTEXPR iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
+  constexpr iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
 
   /** Advances the begin iterator to ``it``. */
   FMT_CONSTEXPR void advance_to(iterator it) {
-    format_str_.remove_prefix(internal::to_unsigned(it - begin()));
+    format_str_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 
   /**
@@ -510,6 +591,8 @@
     the next argument index and switches to the automatic indexing.
    */
   FMT_CONSTEXPR int next_arg_id() {
+    // Don't check if the argument id is valid to avoid overhead and because it
+    // will be checked during formatting anyway.
     if (next_arg_id_ >= 0) return next_arg_id_++;
     on_error("cannot switch from manual to automatic argument indexing");
     return 0;
@@ -532,20 +615,15 @@
     ErrorHandler::on_error(message);
   }
 
-  FMT_CONSTEXPR ErrorHandler error_handler() const { return *this; }
+  constexpr ErrorHandler error_handler() const { return *this; }
 };
 
 using format_parse_context = basic_format_parse_context<char>;
 using wformat_parse_context = basic_format_parse_context<wchar_t>;
 
-template <typename Char, typename ErrorHandler = internal::error_handler>
-using basic_parse_context FMT_DEPRECATED_ALIAS =
-    basic_format_parse_context<Char, ErrorHandler>;
-using parse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<char>;
-using wparse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<wchar_t>;
-
 template <typename Context> class basic_format_arg;
 template <typename Context> class basic_format_args;
+template <typename Context> class dynamic_format_arg_store;
 
 // A formatter for objects of type T.
 template <typename T, typename Char = char, typename Enable = void>
@@ -554,111 +632,18 @@
   formatter() = delete;
 };
 
-template <typename T, typename Char, typename Enable = void>
-struct FMT_DEPRECATED convert_to_int
-    : bool_constant<!std::is_arithmetic<T>::value &&
-                    std::is_convertible<T, int>::value> {};
-
 // Specifies if T has an enabled formatter specialization. A type can be
 // formattable even if it doesn't have a formatter e.g. via a conversion.
 template <typename T, typename Context>
 using has_formatter =
     std::is_constructible<typename Context::template formatter_type<T>>;
 
-namespace internal {
+// Checks whether T is a container with contiguous storage.
+template <typename T> struct is_contiguous : std::false_type {};
+template <typename Char>
+struct is_contiguous<std::basic_string<Char>> : std::true_type {};
 
-/** A contiguous memory buffer with an optional growing ability. */
-template <typename T> class buffer {
- private:
-  T* ptr_;
-  std::size_t size_;
-  std::size_t capacity_;
-
- protected:
-  // Don't initialize ptr_ since it is not accessed to save a few cycles.
-  buffer(std::size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
-
-  buffer(T* p = nullptr, std::size_t sz = 0, std::size_t cap = 0) FMT_NOEXCEPT
-      : ptr_(p),
-        size_(sz),
-        capacity_(cap) {}
-
-  /** Sets the buffer data and capacity. */
-  void set(T* buf_data, std::size_t buf_capacity) FMT_NOEXCEPT {
-    ptr_ = buf_data;
-    capacity_ = buf_capacity;
-  }
-
-  /** Increases the buffer capacity to hold at least *capacity* elements. */
-  virtual void grow(std::size_t capacity) = 0;
-
- public:
-  using value_type = T;
-  using const_reference = const T&;
-
-  buffer(const buffer&) = delete;
-  void operator=(const buffer&) = delete;
-  virtual ~buffer() = default;
-
-  T* begin() FMT_NOEXCEPT { return ptr_; }
-  T* end() FMT_NOEXCEPT { return ptr_ + size_; }
-
-  /** Returns the size of this buffer. */
-  std::size_t size() const FMT_NOEXCEPT { return size_; }
-
-  /** Returns the capacity of this buffer. */
-  std::size_t capacity() const FMT_NOEXCEPT { return capacity_; }
-
-  /** Returns a pointer to the buffer data. */
-  T* data() FMT_NOEXCEPT { return ptr_; }
-
-  /** Returns a pointer to the buffer data. */
-  const T* data() const FMT_NOEXCEPT { return ptr_; }
-
-  /**
-    Resizes the buffer. If T is a POD type new elements may not be initialized.
-   */
-  void resize(std::size_t new_size) {
-    reserve(new_size);
-    size_ = new_size;
-  }
-
-  /** Clears this buffer. */
-  void clear() { size_ = 0; }
-
-  /** Reserves space to store at least *capacity* elements. */
-  void reserve(std::size_t new_capacity) {
-    if (new_capacity > capacity_) grow(new_capacity);
-  }
-
-  void push_back(const T& value) {
-    reserve(size_ + 1);
-    ptr_[size_++] = value;
-  }
-
-  /** Appends data to the end of the buffer. */
-  template <typename U> void append(const U* begin, const U* end);
-
-  T& operator[](std::size_t index) { return ptr_[index]; }
-  const T& operator[](std::size_t index) const { return ptr_[index]; }
-};
-
-// A container-backed buffer.
-template <typename Container>
-class container_buffer : public buffer<typename Container::value_type> {
- private:
-  Container& container_;
-
- protected:
-  void grow(std::size_t capacity) FMT_OVERRIDE {
-    container_.resize(capacity);
-    this->set(&container_[0], capacity);
-  }
-
- public:
-  explicit container_buffer(Container& c)
-      : buffer<typename Container::value_type>(c.size()), container_(c) {}
-};
+namespace detail {
 
 // Extracts a reference to the container from back_insert_iterator.
 template <typename Container>
@@ -671,6 +656,242 @@
   return *accessor(it).container;
 }
 
+/**
+  \rst
+  A contiguous memory buffer with an optional growing ability. It is an internal
+  class and shouldn't be used directly, only via `~fmt::basic_memory_buffer`.
+  \endrst
+ */
+template <typename T> class buffer {
+ private:
+  T* ptr_;
+  size_t size_;
+  size_t capacity_;
+
+ protected:
+  // Don't initialize ptr_ since it is not accessed to save a few cycles.
+  FMT_SUPPRESS_MSC_WARNING(26495)
+  buffer(size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
+
+  buffer(T* p = nullptr, size_t sz = 0, size_t cap = 0) FMT_NOEXCEPT
+      : ptr_(p),
+        size_(sz),
+        capacity_(cap) {}
+
+  ~buffer() = default;
+
+  /** Sets the buffer data and capacity. */
+  void set(T* buf_data, size_t buf_capacity) FMT_NOEXCEPT {
+    ptr_ = buf_data;
+    capacity_ = buf_capacity;
+  }
+
+  /** Increases the buffer capacity to hold at least *capacity* elements. */
+  virtual void grow(size_t capacity) = 0;
+
+ public:
+  using value_type = T;
+  using const_reference = const T&;
+
+  buffer(const buffer&) = delete;
+  void operator=(const buffer&) = delete;
+
+  T* begin() FMT_NOEXCEPT { return ptr_; }
+  T* end() FMT_NOEXCEPT { return ptr_ + size_; }
+
+  const T* begin() const FMT_NOEXCEPT { return ptr_; }
+  const T* end() const FMT_NOEXCEPT { return ptr_ + size_; }
+
+  /** Returns the size of this buffer. */
+  size_t size() const FMT_NOEXCEPT { return size_; }
+
+  /** Returns the capacity of this buffer. */
+  size_t capacity() const FMT_NOEXCEPT { return capacity_; }
+
+  /** Returns a pointer to the buffer data. */
+  T* data() FMT_NOEXCEPT { return ptr_; }
+
+  /** Returns a pointer to the buffer data. */
+  const T* data() const FMT_NOEXCEPT { return ptr_; }
+
+  /** Clears this buffer. */
+  void clear() { size_ = 0; }
+
+  // Tries resizing the buffer to contain *count* elements. If T is a POD type
+  // the new elements may not be initialized.
+  void try_resize(size_t count) {
+    try_reserve(count);
+    size_ = count <= capacity_ ? count : capacity_;
+  }
+
+  // Tries increasing the buffer capacity to *new_capacity*. It can increase the
+  // capacity by a smaller amount than requested but guarantees there is space
+  // for at least one additional element either by increasing the capacity or by
+  // flushing the buffer if it is full.
+  void try_reserve(size_t new_capacity) {
+    if (new_capacity > capacity_) grow(new_capacity);
+  }
+
+  void push_back(const T& value) {
+    try_reserve(size_ + 1);
+    ptr_[size_++] = value;
+  }
+
+  /** Appends data to the end of the buffer. */
+  template <typename U> void append(const U* begin, const U* end);
+
+  template <typename I> T& operator[](I index) { return ptr_[index]; }
+  template <typename I> const T& operator[](I index) const {
+    return ptr_[index];
+  }
+};
+
+struct buffer_traits {
+  explicit buffer_traits(size_t) {}
+  size_t count() const { return 0; }
+  size_t limit(size_t size) { return size; }
+};
+
+class fixed_buffer_traits {
+ private:
+  size_t count_ = 0;
+  size_t limit_;
+
+ public:
+  explicit fixed_buffer_traits(size_t limit) : limit_(limit) {}
+  size_t count() const { return count_; }
+  size_t limit(size_t size) {
+    size_t n = limit_ > count_ ? limit_ - count_ : 0;
+    count_ += size;
+    return size < n ? size : n;
+  }
+};
+
+// A buffer that writes to an output iterator when flushed.
+template <typename OutputIt, typename T, typename Traits = buffer_traits>
+class iterator_buffer final : public Traits, public buffer<T> {
+ private:
+  OutputIt out_;
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
+
+ protected:
+  void grow(size_t) final FMT_OVERRIDE {
+    if (this->size() == buffer_size) flush();
+  }
+  void flush();
+
+ public:
+  explicit iterator_buffer(OutputIt out, size_t n = buffer_size)
+      : Traits(n),
+        buffer<T>(data_, 0, buffer_size),
+        out_(out) {}
+  ~iterator_buffer() { flush(); }
+
+  OutputIt out() {
+    flush();
+    return out_;
+  }
+  size_t count() const { return Traits::count() + this->size(); }
+};
+
+template <typename T> class iterator_buffer<T*, T> final : public buffer<T> {
+ protected:
+  void grow(size_t) final FMT_OVERRIDE {}
+
+ public:
+  explicit iterator_buffer(T* out, size_t = 0) : buffer<T>(out, 0, ~size_t()) {}
+
+  T* out() { return &*this->end(); }
+};
+
+// A buffer that writes to a container with the contiguous storage.
+template <typename Container>
+class iterator_buffer<std::back_insert_iterator<Container>,
+                      enable_if_t<is_contiguous<Container>::value,
+                                  typename Container::value_type>>
+    final : public buffer<typename Container::value_type> {
+ private:
+  Container& container_;
+
+ protected:
+  void grow(size_t capacity) final FMT_OVERRIDE {
+    container_.resize(capacity);
+    this->set(&container_[0], capacity);
+  }
+
+ public:
+  explicit iterator_buffer(Container& c)
+      : buffer<typename Container::value_type>(c.size()), container_(c) {}
+  explicit iterator_buffer(std::back_insert_iterator<Container> out, size_t = 0)
+      : iterator_buffer(get_container(out)) {}
+  std::back_insert_iterator<Container> out() {
+    return std::back_inserter(container_);
+  }
+};
+
+// A buffer that counts the number of code units written discarding the output.
+template <typename T = char> class counting_buffer final : public buffer<T> {
+ private:
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
+  size_t count_ = 0;
+
+ protected:
+  void grow(size_t) final FMT_OVERRIDE {
+    if (this->size() != buffer_size) return;
+    count_ += this->size();
+    this->clear();
+  }
+
+ public:
+  counting_buffer() : buffer<T>(data_, 0, buffer_size) {}
+
+  size_t count() { return count_ + this->size(); }
+};
+
+// An output iterator that appends to the buffer.
+// It is used to reduce symbol sizes for the common case.
+template <typename T>
+class buffer_appender : public std::back_insert_iterator<buffer<T>> {
+  using base = std::back_insert_iterator<buffer<T>>;
+
+ public:
+  explicit buffer_appender(buffer<T>& buf) : base(buf) {}
+  buffer_appender(base it) : base(it) {}
+
+  buffer_appender& operator++() {
+    base::operator++();
+    return *this;
+  }
+
+  buffer_appender operator++(int) {
+    buffer_appender tmp = *this;
+    ++*this;
+    return tmp;
+  }
+};
+
+// Maps an output iterator into a buffer.
+template <typename T, typename OutputIt>
+iterator_buffer<OutputIt, T> get_buffer(OutputIt);
+template <typename T> buffer<T>& get_buffer(buffer_appender<T>);
+
+template <typename OutputIt> OutputIt get_buffer_init(OutputIt out) {
+  return out;
+}
+template <typename T> buffer<T>& get_buffer_init(buffer_appender<T> out) {
+  return get_container(out);
+}
+
+template <typename Buffer>
+auto get_iterator(Buffer& buf) -> decltype(buf.out()) {
+  return buf.out();
+}
+template <typename T> buffer_appender<T> get_iterator(buffer<T>& buf) {
+  return buffer_appender<T>(buf);
+}
+
 template <typename T, typename Char = char, typename Enable = void>
 struct fallback_formatter {
   fallback_formatter() = delete;
@@ -681,12 +902,80 @@
 using has_fallback_formatter =
     std::is_constructible<fallback_formatter<T, typename Context::char_type>>;
 
-template <typename Char> struct named_arg_base;
-template <typename T, typename Char> struct named_arg;
+struct view {};
 
-enum type {
+template <typename Char, typename T> struct named_arg : view {
+  const Char* name;
+  const T& value;
+  named_arg(const Char* n, const T& v) : name(n), value(v) {}
+};
+
+template <typename Char> struct named_arg_info {
+  const Char* name;
+  int id;
+};
+
+template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+struct arg_data {
+  // args_[0].named_args points to named_args_ to avoid bloating format_args.
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  T args_[1 + (NUM_ARGS != 0 ? NUM_ARGS : +1)];
+  named_arg_info<Char> named_args_[NUM_NAMED_ARGS];
+
+  template <typename... U>
+  arg_data(const U&... init) : args_{T(named_args_, NUM_NAMED_ARGS), init...} {}
+  arg_data(const arg_data& other) = delete;
+  const T* args() const { return args_ + 1; }
+  named_arg_info<Char>* named_args() { return named_args_; }
+};
+
+template <typename T, typename Char, size_t NUM_ARGS>
+struct arg_data<T, Char, NUM_ARGS, 0> {
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  T args_[NUM_ARGS != 0 ? NUM_ARGS : +1];
+
+  template <typename... U>
+  FMT_INLINE arg_data(const U&... init) : args_{init...} {}
+  FMT_INLINE const T* args() const { return args_; }
+  FMT_INLINE std::nullptr_t named_args() { return nullptr; }
+};
+
+template <typename Char>
+inline void init_named_args(named_arg_info<Char>*, int, int) {}
+
+template <typename Char, typename T, typename... Tail>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const T&, const Tail&... args) {
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
+
+template <typename Char, typename T, typename... Tail>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const named_arg<Char, T>& arg,
+                     const Tail&... args) {
+  named_args[named_arg_count++] = {arg.name, arg_count};
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
+
+template <typename... Args>
+FMT_INLINE void init_named_args(std::nullptr_t, int, int, const Args&...) {}
+
+template <typename T> struct is_named_arg : std::false_type {};
+
+template <typename T, typename Char>
+struct is_named_arg<named_arg<Char, T>> : std::true_type {};
+
+template <bool B = false> constexpr size_t count() { return B ? 1 : 0; }
+template <bool B1, bool B2, bool... Tail> constexpr size_t count() {
+  return (B1 ? 1 : 0) + count<B2, Tail...>();
+}
+
+template <typename... Args> constexpr size_t count_named_args() {
+  return count<is_named_arg<Args>::value...>();
+}
+
+enum class type {
   none_type,
-  named_arg_type,
   // Integer types should go first,
   int_type,
   uint_type,
@@ -710,13 +999,13 @@
 
 // Maps core type T to the corresponding type enum constant.
 template <typename T, typename Char>
-struct type_constant : std::integral_constant<type, custom_type> {};
+struct type_constant : std::integral_constant<type, type::custom_type> {};
 
 #define FMT_TYPE_CONSTANT(Type, constant) \
   template <typename Char>                \
-  struct type_constant<Type, Char> : std::integral_constant<type, constant> {}
+  struct type_constant<Type, Char>        \
+      : std::integral_constant<type, type::constant> {}
 
-FMT_TYPE_CONSTANT(const named_arg_base<Char>&, named_arg_type);
 FMT_TYPE_CONSTANT(int, int_type);
 FMT_TYPE_CONSTANT(unsigned, uint_type);
 FMT_TYPE_CONSTANT(long long, long_long_type);
@@ -732,23 +1021,26 @@
 FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
 FMT_TYPE_CONSTANT(const void*, pointer_type);
 
-FMT_CONSTEXPR bool is_integral_type(type t) {
-  FMT_ASSERT(t != named_arg_type, "invalid argument type");
-  return t > none_type && t <= last_integer_type;
+constexpr bool is_integral_type(type t) {
+  return t > type::none_type && t <= type::last_integer_type;
 }
 
-FMT_CONSTEXPR bool is_arithmetic_type(type t) {
-  FMT_ASSERT(t != named_arg_type, "invalid argument type");
-  return t > none_type && t <= last_numeric_type;
+constexpr bool is_arithmetic_type(type t) {
+  return t > type::none_type && t <= type::last_numeric_type;
 }
 
 template <typename Char> struct string_value {
   const Char* data;
-  std::size_t size;
+  size_t size;
+};
+
+template <typename Char> struct named_arg_value {
+  const named_arg_info<Char>* data;
+  size_t size;
 };
 
 template <typename Context> struct custom_value {
-  using parse_context = basic_format_parse_context<typename Context::char_type>;
+  using parse_context = typename Context::parse_context_type;
   const void* value;
   void (*format)(const void* arg, parse_context& parse_ctx, Context& ctx);
 };
@@ -773,28 +1065,30 @@
     const void* pointer;
     string_value<char_type> string;
     custom_value<Context> custom;
-    const named_arg_base<char_type>* named_arg;
+    named_arg_value<char_type> named_args;
   };
 
-  FMT_CONSTEXPR value(int val = 0) : int_value(val) {}
-  FMT_CONSTEXPR value(unsigned val) : uint_value(val) {}
-  value(long long val) : long_long_value(val) {}
-  value(unsigned long long val) : ulong_long_value(val) {}
-  value(int128_t val) : int128_value(val) {}
-  value(uint128_t val) : uint128_value(val) {}
-  value(float val) : float_value(val) {}
-  value(double val) : double_value(val) {}
-  value(long double val) : long_double_value(val) {}
-  value(bool val) : bool_value(val) {}
-  value(char_type val) : char_value(val) {}
-  value(const char_type* val) { string.data = val; }
-  value(basic_string_view<char_type> val) {
+  constexpr FMT_INLINE value(int val = 0) : int_value(val) {}
+  constexpr FMT_INLINE value(unsigned val) : uint_value(val) {}
+  FMT_INLINE value(long long val) : long_long_value(val) {}
+  FMT_INLINE value(unsigned long long val) : ulong_long_value(val) {}
+  FMT_INLINE value(int128_t val) : int128_value(val) {}
+  FMT_INLINE value(uint128_t val) : uint128_value(val) {}
+  FMT_INLINE value(float val) : float_value(val) {}
+  FMT_INLINE value(double val) : double_value(val) {}
+  FMT_INLINE value(long double val) : long_double_value(val) {}
+  FMT_INLINE value(bool val) : bool_value(val) {}
+  FMT_INLINE value(char_type val) : char_value(val) {}
+  FMT_INLINE value(const char_type* val) { string.data = val; }
+  FMT_INLINE value(basic_string_view<char_type> val) {
     string.data = val.data();
     string.size = val.size();
   }
-  value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const named_arg_info<char_type>* args, size_t size)
+      : named_args{args, size} {}
 
-  template <typename T> value(const T& val) {
+  template <typename T> FMT_INLINE value(const T& val) {
     custom.value = &val;
     // Get the formatter type through the context to allow different contexts
     // have different extension points, e.g. `formatter<T>` for `format` and
@@ -805,14 +1099,12 @@
                          fallback_formatter<T, char_type>>>;
   }
 
-  value(const named_arg_base<char_type>& val) { named_arg = &val; }
-
  private:
   // Formats an argument of a custom type, such as a user-defined class.
   template <typename T, typename Formatter>
-  static void format_custom_arg(
-      const void* arg, basic_format_parse_context<char_type>& parse_ctx,
-      Context& ctx) {
+  static void format_custom_arg(const void* arg,
+                                typename Context::parse_context_type& parse_ctx,
+                                Context& ctx) {
     Formatter f;
     parse_ctx.advance_to(f.parse(parse_ctx));
     ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
@@ -828,6 +1120,8 @@
 using long_type = conditional_t<long_short, int, long long>;
 using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
 
+struct unformattable {};
+
 // Maps formatting arguments to core types.
 template <typename Context> struct arg_mapper {
   using char_type = typename Context::char_type;
@@ -869,7 +1163,8 @@
   template <typename T,
             FMT_ENABLE_IF(
                 std::is_constructible<basic_string_view<char_type>, T>::value &&
-                !is_string<T>::value)>
+                !is_string<T>::value && !has_formatter<T, Context>::value &&
+                !has_fallback_formatter<T, Context>::value)>
   FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
     return basic_string_view<char_type>(val);
   }
@@ -878,7 +1173,8 @@
       FMT_ENABLE_IF(
           std::is_constructible<std_string_view<char_type>, T>::value &&
           !std::is_constructible<basic_string_view<char_type>, T>::value &&
-          !is_string<T>::value)>
+          !is_string<T>::value && !has_formatter<T, Context>::value &&
+          !has_fallback_formatter<T, Context>::value)>
   FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
     return std_string_view<char_type>(val);
   }
@@ -890,6 +1186,14 @@
     static_assert(std::is_same<char_type, char>::value, "invalid string type");
     return reinterpret_cast<const char*>(val);
   }
+  FMT_CONSTEXPR const char* map(signed char* val) {
+    const auto* const_val = val;
+    return map(const_val);
+  }
+  FMT_CONSTEXPR const char* map(unsigned char* val) {
+    const auto* const_val = val;
+    return map(const_val);
+  }
 
   FMT_CONSTEXPR const void* map(void* val) { return val; }
   FMT_CONSTEXPR const void* map(const void* val) { return val; }
@@ -907,14 +1211,13 @@
             FMT_ENABLE_IF(std::is_enum<T>::value &&
                           !has_formatter<T, Context>::value &&
                           !has_fallback_formatter<T, Context>::value)>
-  FMT_CONSTEXPR auto map(const T& val) -> decltype(
-      map(static_cast<typename std::underlying_type<T>::type>(val))) {
+  FMT_CONSTEXPR auto map(const T& val)
+      -> decltype(std::declval<arg_mapper>().map(
+          static_cast<typename std::underlying_type<T>::type>(val))) {
     return map(static_cast<typename std::underlying_type<T>::type>(val));
   }
   template <typename T,
             FMT_ENABLE_IF(!is_string<T>::value && !is_char<T>::value &&
-                          !std::is_constructible<basic_string_view<char_type>,
-                                                 T>::value &&
                           (has_formatter<T, Context>::value ||
                            has_fallback_formatter<T, Context>::value))>
   FMT_CONSTEXPR const T& map(const T& val) {
@@ -922,12 +1225,12 @@
   }
 
   template <typename T>
-  FMT_CONSTEXPR const named_arg_base<char_type>& map(
-      const named_arg<T, char_type>& val) {
-    auto arg = make_arg<Context>(val.value);
-    std::memcpy(val.data, &arg, sizeof(arg));
-    return val;
+  FMT_CONSTEXPR auto map(const named_arg<char_type, T>& val)
+      -> decltype(std::declval<arg_mapper>().map(val.value)) {
+    return map(val.value);
   }
+
+  unformattable map(...) { return {}; }
 };
 
 // A type constant after applying arg_mapper<Context>.
@@ -936,23 +1239,22 @@
     type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
                   typename Context::char_type>;
 
-enum { packed_arg_bits = 5 };
+enum { packed_arg_bits = 4 };
 // Maximum number of arguments with packed types.
-enum { max_packed_args = 63 / packed_arg_bits };
+enum { max_packed_args = 62 / packed_arg_bits };
 enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
-
-template <typename Context> class arg_map;
-}  // namespace internal
+enum : unsigned long long { has_named_args_bit = 1ULL << 62 };
+}  // namespace detail
 
 // A formatting argument. It is a trivially copyable/constructible type to
 // allow storage in basic_memory_buffer.
 template <typename Context> class basic_format_arg {
  private:
-  internal::value<Context> value_;
-  internal::type type_;
+  detail::value<Context> value_;
+  detail::type type_;
 
   template <typename ContextType, typename T>
-  friend FMT_CONSTEXPR basic_format_arg<ContextType> internal::make_arg(
+  friend FMT_CONSTEXPR basic_format_arg<ContextType> detail::make_arg(
       const T& value);
 
   template <typename Visitor, typename Ctx>
@@ -961,34 +1263,40 @@
       -> decltype(vis(0));
 
   friend class basic_format_args<Context>;
-  friend class internal::arg_map<Context>;
+  friend class dynamic_format_arg_store<Context>;
 
   using char_type = typename Context::char_type;
 
+  template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+  friend struct detail::arg_data;
+
+  basic_format_arg(const detail::named_arg_info<char_type>* args, size_t size)
+      : value_(args, size) {}
+
  public:
   class handle {
    public:
-    explicit handle(internal::custom_value<Context> custom) : custom_(custom) {}
+    explicit handle(detail::custom_value<Context> custom) : custom_(custom) {}
 
-    void format(basic_format_parse_context<char_type>& parse_ctx,
+    void format(typename Context::parse_context_type& parse_ctx,
                 Context& ctx) const {
       custom_.format(custom_.value, parse_ctx, ctx);
     }
 
    private:
-    internal::custom_value<Context> custom_;
+    detail::custom_value<Context> custom_;
   };
 
-  FMT_CONSTEXPR basic_format_arg() : type_(internal::none_type) {}
+  constexpr basic_format_arg() : type_(detail::type::none_type) {}
 
-  FMT_CONSTEXPR explicit operator bool() const FMT_NOEXCEPT {
-    return type_ != internal::none_type;
+  constexpr explicit operator bool() const FMT_NOEXCEPT {
+    return type_ != detail::type::none_type;
   }
 
-  internal::type type() const { return type_; }
+  detail::type type() const { return type_; }
 
-  bool is_integral() const { return internal::is_integral_type(type_); }
-  bool is_arithmetic() const { return internal::is_arithmetic_type(type_); }
+  bool is_integral() const { return detail::is_integral_type(type_); }
+  bool is_arithmetic() const { return detail::is_arithmetic_type(type_); }
 };
 
 /**
@@ -999,92 +1307,86 @@
   \endrst
  */
 template <typename Visitor, typename Context>
-FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
-                                    const basic_format_arg<Context>& arg)
-    -> decltype(vis(0)) {
+FMT_CONSTEXPR_DECL FMT_INLINE auto visit_format_arg(
+    Visitor&& vis, const basic_format_arg<Context>& arg) -> decltype(vis(0)) {
   using char_type = typename Context::char_type;
   switch (arg.type_) {
-  case internal::none_type:
+  case detail::type::none_type:
     break;
-  case internal::named_arg_type:
-    FMT_ASSERT(false, "invalid argument type");
-    break;
-  case internal::int_type:
+  case detail::type::int_type:
     return vis(arg.value_.int_value);
-  case internal::uint_type:
+  case detail::type::uint_type:
     return vis(arg.value_.uint_value);
-  case internal::long_long_type:
+  case detail::type::long_long_type:
     return vis(arg.value_.long_long_value);
-  case internal::ulong_long_type:
+  case detail::type::ulong_long_type:
     return vis(arg.value_.ulong_long_value);
 #if FMT_USE_INT128
-  case internal::int128_type:
+  case detail::type::int128_type:
     return vis(arg.value_.int128_value);
-  case internal::uint128_type:
+  case detail::type::uint128_type:
     return vis(arg.value_.uint128_value);
 #else
-  case internal::int128_type:
-  case internal::uint128_type:
+  case detail::type::int128_type:
+  case detail::type::uint128_type:
     break;
 #endif
-  case internal::bool_type:
+  case detail::type::bool_type:
     return vis(arg.value_.bool_value);
-  case internal::char_type:
+  case detail::type::char_type:
     return vis(arg.value_.char_value);
-  case internal::float_type:
+  case detail::type::float_type:
     return vis(arg.value_.float_value);
-  case internal::double_type:
+  case detail::type::double_type:
     return vis(arg.value_.double_value);
-  case internal::long_double_type:
+  case detail::type::long_double_type:
     return vis(arg.value_.long_double_value);
-  case internal::cstring_type:
+  case detail::type::cstring_type:
     return vis(arg.value_.string.data);
-  case internal::string_type:
+  case detail::type::string_type:
     return vis(basic_string_view<char_type>(arg.value_.string.data,
                                             arg.value_.string.size));
-  case internal::pointer_type:
+  case detail::type::pointer_type:
     return vis(arg.value_.pointer);
-  case internal::custom_type:
+  case detail::type::custom_type:
     return vis(typename basic_format_arg<Context>::handle(arg.value_.custom));
   }
   return vis(monostate());
 }
 
-namespace internal {
-// A map from argument names to their values for named arguments.
-template <typename Context> class arg_map {
- private:
-  using char_type = typename Context::char_type;
+template <typename T> struct formattable : std::false_type {};
 
-  struct entry {
-    basic_string_view<char_type> name;
-    basic_format_arg<Context> arg;
-  };
+namespace detail {
 
-  entry* map_;
-  unsigned size_;
+// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
+template <typename... Ts> struct void_t_impl { using type = void; };
+template <typename... Ts>
+using void_t = typename detail::void_t_impl<Ts...>::type;
 
-  void push_back(value<Context> val) {
-    const auto& named = *val.named_arg;
-    map_[size_] = {named.name, named.template deserialize<Context>()};
-    ++size_;
-  }
+template <typename It, typename T, typename Enable = void>
+struct is_output_iterator : std::false_type {};
 
- public:
-  arg_map(const arg_map&) = delete;
-  void operator=(const arg_map&) = delete;
-  arg_map() : map_(nullptr), size_(0) {}
-  void init(const basic_format_args<Context>& args);
-  ~arg_map() { delete[] map_; }
+template <typename It, typename T>
+struct is_output_iterator<
+    It, T,
+    void_t<typename std::iterator_traits<It>::iterator_category,
+           decltype(*std::declval<It>() = std::declval<T>())>>
+    : std::true_type {};
 
-  basic_format_arg<Context> find(basic_string_view<char_type> name) const {
-    // The list is unsorted, so just return the first matching name.
-    for (entry *it = map_, *end = map_ + size_; it != end; ++it) {
-      if (it->name == name) return it->arg;
-    }
-    return {};
-  }
-};
+template <typename OutputIt>
+struct is_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_back_insert_iterator<std::back_insert_iterator<Container>>
+    : std::true_type {};
+
+template <typename OutputIt>
+struct is_contiguous_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
+    : is_contiguous<Container> {};
+template <typename Char>
+struct is_contiguous_back_insert_iterator<buffer_appender<Char>>
+    : std::true_type {};
 
 // A type-erased reference to an std::locale to avoid heavy <locale> include.
 class locale_ref {
@@ -1104,7 +1406,7 @@
 
 template <typename Context, typename Arg, typename... Args>
 constexpr unsigned long long encode_types() {
-  return mapped_type_constant<Arg, Context>::value |
+  return static_cast<unsigned>(mapped_type_constant<Arg, Context>::value) |
          (encode_types<Context, Args...>() << packed_arg_bits);
 }
 
@@ -1116,18 +1418,73 @@
   return arg;
 }
 
-template <bool IS_PACKED, typename Context, typename T,
-          FMT_ENABLE_IF(IS_PACKED)>
-inline value<Context> make_arg(const T& val) {
-  return arg_mapper<Context>().map(val);
+template <typename T> int check(unformattable) {
+  static_assert(
+      formattable<T>(),
+      "Cannot format an argument. To make type T formattable provide a "
+      "formatter<T> specialization: https://fmt.dev/latest/api.html#udt");
+  return 0;
+}
+template <typename T, typename U> inline const U& check(const U& val) {
+  return val;
 }
 
-template <bool IS_PACKED, typename Context, typename T,
+// The type template parameter is there to avoid an ODR violation when using
+// a fallback formatter in one translation unit and an implicit conversion in
+// another (not recommended).
+template <bool IS_PACKED, typename Context, type, typename T,
+          FMT_ENABLE_IF(IS_PACKED)>
+inline value<Context> make_arg(const T& val) {
+  return check<T>(arg_mapper<Context>().map(val));
+}
+
+template <bool IS_PACKED, typename Context, type, typename T,
           FMT_ENABLE_IF(!IS_PACKED)>
 inline basic_format_arg<Context> make_arg(const T& value) {
   return make_arg<Context>(value);
 }
-}  // namespace internal
+
+template <typename T> struct is_reference_wrapper : std::false_type {};
+template <typename T>
+struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};
+
+template <typename T> const T& unwrap(const T& v) { return v; }
+template <typename T> const T& unwrap(const std::reference_wrapper<T>& v) {
+  return static_cast<const T&>(v);
+}
+
+class dynamic_arg_list {
+  // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for
+  // templates it doesn't complain about inability to deduce single translation
+  // unit for placing vtable. So storage_node_base is made a fake template.
+  template <typename = void> struct node {
+    virtual ~node() = default;
+    std::unique_ptr<node<>> next;
+  };
+
+  template <typename T> struct typed_node : node<> {
+    T value;
+
+    template <typename Arg>
+    FMT_CONSTEXPR typed_node(const Arg& arg) : value(arg) {}
+
+    template <typename Char>
+    FMT_CONSTEXPR typed_node(const basic_string_view<Char>& arg)
+        : value(arg.data(), arg.size()) {}
+  };
+
+  std::unique_ptr<node<>> head_;
+
+ public:
+  template <typename T, typename Arg> const T& push(const Arg& arg) {
+    auto new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
+    auto& value = new_node->value;
+    new_node->next = std::move(head_);
+    head_ = std::move(new_node);
+    return value;
+  }
+};
+}  // namespace detail
 
 // Formatting context.
 template <typename OutputIt, typename Char> class basic_format_context {
@@ -1138,12 +1495,12 @@
  private:
   OutputIt out_;
   basic_format_args<basic_format_context> args_;
-  internal::arg_map<basic_format_context> map_;
-  internal::locale_ref loc_;
+  detail::locale_ref loc_;
 
  public:
   using iterator = OutputIt;
   using format_arg = basic_format_arg<basic_format_context>;
+  using parse_context_type = basic_format_parse_context<Char>;
   template <typename T> using formatter_type = formatter<T, char_type>;
 
   basic_format_context(const basic_format_context&) = delete;
@@ -1154,34 +1511,38 @@
    */
   basic_format_context(OutputIt out,
                        basic_format_args<basic_format_context> ctx_args,
-                       internal::locale_ref loc = internal::locale_ref())
+                       detail::locale_ref loc = detail::locale_ref())
       : out_(out), args_(ctx_args), loc_(loc) {}
 
   format_arg arg(int id) const { return args_.get(id); }
+  format_arg arg(basic_string_view<char_type> name) { return args_.get(name); }
+  int arg_id(basic_string_view<char_type> name) { return args_.get_id(name); }
+  const basic_format_args<basic_format_context>& args() const { return args_; }
 
-  // Checks if manual indexing is used and returns the argument with the
-  // specified name.
-  format_arg arg(basic_string_view<char_type> name);
-
-  internal::error_handler error_handler() { return {}; }
+  detail::error_handler error_handler() { return {}; }
   void on_error(const char* message) { error_handler().on_error(message); }
 
   // Returns an iterator to the beginning of the output range.
   iterator out() { return out_; }
 
   // Advances the begin iterator to ``it``.
-  void advance_to(iterator it) { out_ = it; }
+  void advance_to(iterator it) {
+    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
+  }
 
-  internal::locale_ref locale() { return loc_; }
+  detail::locale_ref locale() { return loc_; }
 };
 
 template <typename Char>
 using buffer_context =
-    basic_format_context<std::back_insert_iterator<internal::buffer<Char>>,
-                         Char>;
+    basic_format_context<detail::buffer_appender<Char>, Char>;
 using format_context = buffer_context<char>;
 using wformat_context = buffer_context<wchar_t>;
 
+// Workaround an alias issue: https://stackoverflow.com/q/62767544/471164.
+#define FMT_BUFFER_CONTEXT(Char) \
+  basic_format_context<detail::buffer_appender<Char>, Char>
+
 /**
   \rst
   An array of references to arguments. It can be implicitly converted into
@@ -1189,31 +1550,50 @@
   such as `~fmt::vformat`.
   \endrst
  */
-template <typename Context, typename... Args> class format_arg_store {
+template <typename Context, typename... Args>
+class format_arg_store
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+    // Workaround a GCC template argument substitution bug.
+    : public basic_format_args<Context>
+#endif
+{
  private:
   static const size_t num_args = sizeof...(Args);
-  static const bool is_packed = num_args < internal::max_packed_args;
+  static const size_t num_named_args = detail::count_named_args<Args...>();
+  static const bool is_packed = num_args <= detail::max_packed_args;
 
-  using value_type = conditional_t<is_packed, internal::value<Context>,
+  using value_type = conditional_t<is_packed, detail::value<Context>,
                                    basic_format_arg<Context>>;
 
-  // If the arguments are not packed, add one more element to mark the end.
-  value_type data_[num_args + (num_args == 0 ? 1 : 0)];
+  detail::arg_data<value_type, typename Context::char_type, num_args,
+                   num_named_args>
+      data_;
 
   friend class basic_format_args<Context>;
 
- public:
-  static constexpr unsigned long long types =
-      is_packed ? internal::encode_types<Context, Args...>()
-                : internal::is_unpacked_bit | num_args;
+  static constexpr unsigned long long desc =
+      (is_packed ? detail::encode_types<Context, Args...>()
+                 : detail::is_unpacked_bit | num_args) |
+      (num_named_args != 0
+           ? static_cast<unsigned long long>(detail::has_named_args_bit)
+           : 0);
 
+ public:
   format_arg_store(const Args&... args)
-      : data_{internal::make_arg<is_packed, Context>(args)...} {}
+      :
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+        basic_format_args<Context>(*this),
+#endif
+        data_{detail::make_arg<
+            is_packed, Context,
+            detail::mapped_type_constant<Args, Context>::value>(args)...} {
+    detail::init_named_args(data_.named_args(), 0, 0, args...);
+  }
 };
 
 /**
   \rst
-  Constructs an `~fmt::format_arg_store` object that contains references to
+  Constructs a `~fmt::format_arg_store` object that contains references to
   arguments and can be implicitly converted to `~fmt::format_args`. `Context`
   can be omitted in which case it defaults to `~fmt::context`.
   See `~fmt::arg` for lifetime considerations.
@@ -1225,56 +1605,266 @@
   return {args...};
 }
 
-/** Formatting arguments. */
+/**
+  \rst
+  Constructs a `~fmt::format_arg_store` object that contains references
+  to arguments and can be implicitly converted to `~fmt::format_args`.
+  If ``format_str`` is a compile-time string then `make_args_checked` checks
+  its validity at compile time.
+  \endrst
+ */
+template <typename... Args, typename S, typename Char = char_t<S>>
+inline auto make_args_checked(const S& format_str,
+                              const remove_reference_t<Args>&... args)
+    -> format_arg_store<buffer_context<Char>, remove_reference_t<Args>...> {
+  static_assert(
+      detail::count<(
+              std::is_base_of<detail::view, remove_reference_t<Args>>::value &&
+              std::is_reference<Args>::value)...>() == 0,
+      "passing views as lvalues is disallowed");
+  detail::check_format_string<Args...>(format_str);
+  return {args...};
+}
+
+/**
+  \rst
+  Returns a named argument to be used in a formatting function. It should only
+  be used in a call to a formatting function.
+
+  **Example**::
+
+    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
+  \endrst
+ */
+template <typename Char, typename T>
+inline detail::named_arg<Char, T> arg(const Char* name, const T& arg) {
+  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
+  return {name, arg};
+}
+
+/**
+  \rst
+  A dynamic version of `fmt::format_arg_store`.
+  It's equipped with a storage to potentially temporary objects which lifetimes
+  could be shorter than the format arguments object.
+
+  It can be implicitly converted into `~fmt::basic_format_args` for passing
+  into type-erased formatting functions such as `~fmt::vformat`.
+  \endrst
+ */
+template <typename Context>
+class dynamic_format_arg_store
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+    // Workaround a GCC template argument substitution bug.
+    : public basic_format_args<Context>
+#endif
+{
+ private:
+  using char_type = typename Context::char_type;
+
+  template <typename T> struct need_copy {
+    static constexpr detail::type mapped_type =
+        detail::mapped_type_constant<T, Context>::value;
+
+    enum {
+      value = !(detail::is_reference_wrapper<T>::value ||
+                std::is_same<T, basic_string_view<char_type>>::value ||
+                std::is_same<T, detail::std_string_view<char_type>>::value ||
+                (mapped_type != detail::type::cstring_type &&
+                 mapped_type != detail::type::string_type &&
+                 mapped_type != detail::type::custom_type))
+    };
+  };
+
+  template <typename T>
+  using stored_type = conditional_t<detail::is_string<T>::value,
+                                    std::basic_string<char_type>, T>;
+
+  // Storage of basic_format_arg must be contiguous.
+  std::vector<basic_format_arg<Context>> data_;
+  std::vector<detail::named_arg_info<char_type>> named_info_;
+
+  // Storage of arguments not fitting into basic_format_arg must grow
+  // without relocation because items in data_ refer to it.
+  detail::dynamic_arg_list dynamic_args_;
+
+  friend class basic_format_args<Context>;
+
+  unsigned long long get_types() const {
+    return detail::is_unpacked_bit | data_.size() |
+           (named_info_.empty()
+                ? 0ULL
+                : static_cast<unsigned long long>(detail::has_named_args_bit));
+  }
+
+  const basic_format_arg<Context>* data() const {
+    return named_info_.empty() ? data_.data() : data_.data() + 1;
+  }
+
+  template <typename T> void emplace_arg(const T& arg) {
+    data_.emplace_back(detail::make_arg<Context>(arg));
+  }
+
+  template <typename T>
+  void emplace_arg(const detail::named_arg<char_type, T>& arg) {
+    if (named_info_.empty()) {
+      constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr};
+      data_.insert(data_.begin(), {zero_ptr, 0});
+    }
+    data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value)));
+    auto pop_one = [](std::vector<basic_format_arg<Context>>* data) {
+      data->pop_back();
+    };
+    std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)>
+        guard{&data_, pop_one};
+    named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)});
+    data_[0].value_.named_args = {named_info_.data(), named_info_.size()};
+    guard.release();
+  }
+
+ public:
+  /**
+    \rst
+    Adds an argument into the dynamic store for later passing to a formatting
+    function.
+
+    Note that custom types and string types (but not string views) are copied
+    into the store dynamically allocating memory if necessary.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      store.push_back(42);
+      store.push_back("abc");
+      store.push_back(1.5f);
+      std::string result = fmt::vformat("{} and {} and {}", store);
+    \endrst
+  */
+  template <typename T> void push_back(const T& arg) {
+    if (detail::const_check(need_copy<T>::value))
+      emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
+    else
+      emplace_arg(detail::unwrap(arg));
+  }
+
+  /**
+    \rst
+    Adds a reference to the argument into the dynamic store for later passing to
+    a formatting function. Supports named arguments wrapped in
+    ``std::reference_wrapper`` via ``std::ref()``/``std::cref()``.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      char str[] = "1234567890";
+      store.push_back(std::cref(str));
+      int a1_val{42};
+      auto a1 = fmt::arg("a1_", a1_val);
+      store.push_back(std::cref(a1));
+
+      // Changing str affects the output but only for string and custom types.
+      str[0] = 'X';
+
+      std::string result = fmt::vformat("{} and {a1_}");
+      assert(result == "X234567890 and 42");
+    \endrst
+  */
+  template <typename T> void push_back(std::reference_wrapper<T> arg) {
+    static_assert(
+        detail::is_named_arg<typename std::remove_cv<T>::type>::value ||
+            need_copy<T>::value,
+        "objects of built-in types and string views are always copied");
+    emplace_arg(arg.get());
+  }
+
+  /**
+    Adds named argument into the dynamic store for later passing to a formatting
+    function. ``std::reference_wrapper`` is supported to avoid copying of the
+    argument.
+  */
+  template <typename T>
+  void push_back(const detail::named_arg<char_type, T>& arg) {
+    const char_type* arg_name =
+        dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str();
+    if (detail::const_check(need_copy<T>::value)) {
+      emplace_arg(
+          fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value)));
+    } else {
+      emplace_arg(fmt::arg(arg_name, arg.value));
+    }
+  }
+
+  /** Erase all elements from the store */
+  void clear() {
+    data_.clear();
+    named_info_.clear();
+    dynamic_args_ = detail::dynamic_arg_list();
+  }
+
+  /**
+    \rst
+    Reserves space to store at least *new_cap* arguments including
+    *new_cap_named* named arguments.
+    \endrst
+  */
+  void reserve(size_t new_cap, size_t new_cap_named) {
+    FMT_ASSERT(new_cap >= new_cap_named,
+               "Set of arguments includes set of named arguments");
+    data_.reserve(new_cap);
+    named_info_.reserve(new_cap_named);
+  }
+};
+
+/**
+  \rst
+  A view of a collection of formatting arguments. To avoid lifetime issues it
+  should only be used as a parameter type in type-erased functions such as
+  ``vformat``::
+
+    void vlog(string_view format_str, format_args args);  // OK
+    format_args args = make_format_args(42);  // Error: dangling reference
+  \endrst
+ */
 template <typename Context> class basic_format_args {
  public:
   using size_type = int;
   using format_arg = basic_format_arg<Context>;
 
  private:
-  // To reduce compiled code size per formatting function call, types of first
-  // max_packed_args arguments are passed in the types_ field.
-  unsigned long long types_;
+  // A descriptor that contains information about formatting arguments.
+  // If the number of arguments is less or equal to max_packed_args then
+  // argument types are passed in the descriptor. This reduces binary code size
+  // per formatting function call.
+  unsigned long long desc_;
   union {
-    // If the number of arguments is less than max_packed_args, the argument
-    // values are stored in values_, otherwise they are stored in args_.
-    // This is done to reduce compiled code size as storing larger objects
+    // If is_packed() returns true then argument values are stored in values_;
+    // otherwise they are stored in args_. This is done to improve cache
+    // locality and reduce compiled code size since storing larger objects
     // may require more code (at least on x86-64) even if the same amount of
     // data is actually copied to stack. It saves ~10% on the bloat test.
-    const internal::value<Context>* values_;
+    const detail::value<Context>* values_;
     const format_arg* args_;
   };
 
-  bool is_packed() const { return (types_ & internal::is_unpacked_bit) == 0; }
-
-  internal::type type(int index) const {
-    int shift = index * internal::packed_arg_bits;
-    unsigned int mask = (1 << internal::packed_arg_bits) - 1;
-    return static_cast<internal::type>((types_ >> shift) & mask);
+  bool is_packed() const { return (desc_ & detail::is_unpacked_bit) == 0; }
+  bool has_named_args() const {
+    return (desc_ & detail::has_named_args_bit) != 0;
   }
 
-  friend class internal::arg_map<Context>;
-
-  void set_data(const internal::value<Context>* values) { values_ = values; }
-  void set_data(const format_arg* args) { args_ = args; }
-
-  format_arg do_get(int index) const {
-    format_arg arg;
-    if (!is_packed()) {
-      auto num_args = max_size();
-      if (index < num_args) arg = args_[index];
-      return arg;
-    }
-    if (index > internal::max_packed_args) return arg;
-    arg.type_ = type(index);
-    if (arg.type_ == internal::none_type) return arg;
-    internal::value<Context>& val = arg.value_;
-    val = values_[index];
-    return arg;
+  detail::type type(int index) const {
+    int shift = index * detail::packed_arg_bits;
+    unsigned int mask = (1 << detail::packed_arg_bits) - 1;
+    return static_cast<detail::type>((desc_ >> shift) & mask);
   }
 
+  basic_format_args(unsigned long long desc,
+                    const detail::value<Context>* values)
+      : desc_(desc), values_(values) {}
+  basic_format_args(unsigned long long desc, const format_arg* args)
+      : desc_(desc), args_(args) {}
+
  public:
-  basic_format_args() : types_(0) {}
+  basic_format_args() : desc_(0) {}
 
   /**
    \rst
@@ -1282,10 +1872,17 @@
    \endrst
    */
   template <typename... Args>
-  basic_format_args(const format_arg_store<Context, Args...>& store)
-      : types_(static_cast<unsigned long long>(store.types)) {
-    set_data(store.data_);
-  }
+  FMT_INLINE basic_format_args(const format_arg_store<Context, Args...>& store)
+      : basic_format_args(store.desc, store.data_.args()) {}
+
+  /**
+   \rst
+   Constructs a `basic_format_args` object from
+   `~fmt::dynamic_format_arg_store`.
+   \endrst
+   */
+  FMT_INLINE basic_format_args(const dynamic_format_arg_store<Context>& store)
+      : basic_format_args(store.get_types(), store.data()) {}
 
   /**
    \rst
@@ -1293,168 +1890,172 @@
    \endrst
    */
   basic_format_args(const format_arg* args, int count)
-      : types_(internal::is_unpacked_bit | internal::to_unsigned(count)) {
-    set_data(args);
+      : basic_format_args(detail::is_unpacked_bit | detail::to_unsigned(count),
+                          args) {}
+
+  /** Returns the argument with the specified id. */
+  format_arg get(int id) const {
+    format_arg arg;
+    if (!is_packed()) {
+      if (id < max_size()) arg = args_[id];
+      return arg;
+    }
+    if (id >= detail::max_packed_args) return arg;
+    arg.type_ = type(id);
+    if (arg.type_ == detail::type::none_type) return arg;
+    arg.value_ = values_[id];
+    return arg;
   }
 
-  /** Returns the argument at specified index. */
-  format_arg get(int index) const {
-    format_arg arg = do_get(index);
-    if (arg.type_ == internal::named_arg_type)
-      arg = arg.value_.named_arg->template deserialize<Context>();
-    return arg;
+  template <typename Char> format_arg get(basic_string_view<Char> name) const {
+    int id = get_id(name);
+    return id >= 0 ? get(id) : format_arg();
+  }
+
+  template <typename Char> int get_id(basic_string_view<Char> name) const {
+    if (!has_named_args()) return -1;
+    const auto& named_args =
+        (is_packed() ? values_[-1] : args_[-1].value_).named_args;
+    for (size_t i = 0; i < named_args.size; ++i) {
+      if (named_args.data[i].name == name) return named_args.data[i].id;
+    }
+    return -1;
   }
 
   int max_size() const {
-    unsigned long long max_packed = internal::max_packed_args;
+    unsigned long long max_packed = detail::max_packed_args;
     return static_cast<int>(is_packed() ? max_packed
-                                        : types_ & ~internal::is_unpacked_bit);
+                                        : desc_ & ~detail::is_unpacked_bit);
   }
 };
 
-/** An alias to ``basic_format_args<context>``. */
+#ifdef FMT_ARM_ABI_COMPATIBILITY
+/** An alias to ``basic_format_args<format_context>``. */
+// Separate types would result in shorter symbols but break ABI compatibility
+// between clang and gcc on ARM (#1919).
+using format_args = basic_format_args<format_context>;
+using wformat_args = basic_format_args<wformat_context>;
+#else
+// DEPRECATED! These are kept for ABI compatibility.
 // It is a separate type rather than an alias to make symbols readable.
 struct format_args : basic_format_args<format_context> {
   template <typename... Args>
-  format_args(Args&&... args)
-      : basic_format_args<format_context>(std::forward<Args>(args)...) {}
+  FMT_INLINE format_args(const Args&... args) : basic_format_args(args...) {}
 };
 struct wformat_args : basic_format_args<wformat_context> {
-  template <typename... Args>
-  wformat_args(Args&&... args)
-      : basic_format_args<wformat_context>(std::forward<Args>(args)...) {}
+  using basic_format_args::basic_format_args;
 };
-
-template <typename Container> struct is_contiguous : std::false_type {};
-
-template <typename Char>
-struct is_contiguous<std::basic_string<Char>> : std::true_type {};
-
-template <typename Char>
-struct is_contiguous<internal::buffer<Char>> : std::true_type {};
-
-namespace internal {
-
-template <typename OutputIt>
-struct is_contiguous_back_insert_iterator : std::false_type {};
-template <typename Container>
-struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
-    : is_contiguous<Container> {};
-
-template <typename Char> struct named_arg_base {
-  basic_string_view<Char> name;
-
-  // Serialized value<context>.
-  mutable char data[sizeof(basic_format_arg<buffer_context<Char>>)];
-
-  named_arg_base(basic_string_view<Char> nm) : name(nm) {}
-
-  template <typename Context> basic_format_arg<Context> deserialize() const {
-    basic_format_arg<Context> arg;
-    std::memcpy(&arg, data, sizeof(basic_format_arg<Context>));
-    return arg;
-  }
-};
-
-template <typename T, typename Char> struct named_arg : named_arg_base<Char> {
-  const T& value;
-
-  named_arg(basic_string_view<Char> name, const T& val)
-      : named_arg_base<Char>(name), value(val) {}
-};
-
-template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
-inline void check_format_string(const S&) {
-#if defined(FMT_ENFORCE_COMPILE_STRING)
-  static_assert(is_compile_string<S>::value,
-                "FMT_ENFORCE_COMPILE_STRING requires all format strings to "
-                "utilize FMT_STRING() or fmt().");
 #endif
-}
-template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
-void check_format_string(S);
 
-struct view {};
-template <bool...> struct bool_pack;
-template <bool... Args>
-using all_true =
-    std::is_same<bool_pack<Args..., true>, bool_pack<true, Args...>>;
+namespace detail {
 
-template <typename... Args, typename S, typename Char = char_t<S>>
-inline format_arg_store<buffer_context<Char>, remove_reference_t<Args>...>
-make_args_checked(const S& format_str,
-                  const remove_reference_t<Args>&... args) {
-  static_assert(all_true<(!std::is_base_of<view, remove_reference_t<Args>>() ||
-                          !std::is_reference<Args>())...>::value,
-                "passing views as lvalues is disallowed");
-  check_format_string<remove_const_t<remove_reference_t<Args>>...>(format_str);
-  return {args...};
-}
+template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+std::basic_string<Char> vformat(
+    basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args);
+
+FMT_API std::string vformat(string_view format_str, format_args args);
 
 template <typename Char>
-std::basic_string<Char> vformat(basic_string_view<Char> format_str,
-                                basic_format_args<buffer_context<Char>> args);
-
-template <typename Char>
-typename buffer_context<Char>::iterator vformat_to(
+void vformat_to(
     buffer<Char>& buf, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<Char>> args);
-}  // namespace internal
+    basic_format_args<FMT_BUFFER_CONTEXT(type_identity_t<Char>)> args,
+    detail::locale_ref loc = {});
 
-/**
-  \rst
-  Returns a named argument to be used in a formatting function.
+template <typename Char, typename Args,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+inline void vprint_mojibake(std::FILE*, basic_string_view<Char>, const Args&) {}
 
-  The named argument holds a reference and does not extend the lifetime
-  of its arguments.
-  Consequently, a dangling reference can accidentally be created.
-  The user should take care to only pass this function temporaries when
-  the named argument is itself a temporary, as per the following example.
-
-  **Example**::
-
-    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
-  \endrst
- */
-template <typename S, typename T, typename Char = char_t<S>>
-inline internal::named_arg<T, Char> arg(const S& name, const T& arg) {
-  static_assert(internal::is_string<S>::value, "");
-  return {name, arg};
-}
-
-// Disable nested named arguments, e.g. ``arg("a", arg("b", 42))``.
-template <typename S, typename T, typename Char>
-void arg(S, internal::named_arg<T, Char>) = delete;
+FMT_API void vprint_mojibake(std::FILE*, string_view, format_args);
+#ifndef _WIN32
+inline void vprint_mojibake(std::FILE*, string_view, format_args) {}
+#endif
+}  // namespace detail
 
 /** Formats a string and writes the output to ``out``. */
 // GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
 // vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
 template <typename OutputIt, typename S, typename Char = char_t<S>,
-          FMT_ENABLE_IF(
-              internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
-OutputIt vformat_to(OutputIt out, const S& format_str,
-                    basic_format_args<buffer_context<Char>> args) {
-  using container = remove_reference_t<decltype(internal::get_container(out))>;
-  internal::container_buffer<container> buf((internal::get_container(out)));
-  internal::vformat_to(buf, to_string_view(format_str), args);
-  return out;
+          bool enable = detail::is_output_iterator<OutputIt, Char>::value>
+auto vformat_to(OutputIt out, const S& format_str,
+                basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> typename std::enable_if<enable, OutputIt>::type {
+  decltype(detail::get_buffer<Char>(out)) buf(detail::get_buffer_init(out));
+  detail::vformat_to(buf, to_string_view(format_str), args);
+  return detail::get_iterator(buf);
 }
 
-template <typename Container, typename S, typename... Args,
-          FMT_ENABLE_IF(
-              is_contiguous<Container>::value&& internal::is_string<S>::value)>
-inline std::back_insert_iterator<Container> format_to(
-    std::back_insert_iterator<Container> out, const S& format_str,
-    Args&&... args) {
-  return vformat_to(
-      out, to_string_view(format_str),
-      {internal::make_args_checked<Args...>(format_str, args...)});
+/**
+ \rst
+ Formats arguments, writes the result to the output iterator ``out`` and returns
+ the iterator past the end of the output range.
+
+ **Example**::
+
+   std::vector<char> out;
+   fmt::format_to(std::back_inserter(out), "{}", 42);
+ \endrst
+ */
+// We cannot use FMT_ENABLE_IF because of a bug in gcc 8.3.
+template <typename OutputIt, typename S, typename... Args,
+          bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value>
+inline auto format_to(OutputIt out, const S& format_str, Args&&... args) ->
+    typename std::enable_if<enable, OutputIt>::type {
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  return vformat_to(out, to_string_view(format_str), vargs);
+}
+
+template <typename OutputIt> struct format_to_n_result {
+  /** Iterator past the end of the output range. */
+  OutputIt out;
+  /** Total (not truncated) output size. */
+  size_t size;
+};
+
+template <typename OutputIt, typename Char, typename... Args,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
+inline format_to_n_result<OutputIt> vformat_to_n(
+    OutputIt out, size_t n, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  detail::iterator_buffer<OutputIt, Char, detail::fixed_buffer_traits> buf(out,
+                                                                           n);
+  detail::vformat_to(buf, format_str, args);
+  return {buf.out(), buf.count()};
+}
+
+/**
+ \rst
+ Formats arguments, writes up to ``n`` characters of the result to the output
+ iterator ``out`` and returns the total output size and the iterator past the
+ end of the output range.
+ \endrst
+ */
+template <typename OutputIt, typename S, typename... Args,
+          bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value>
+inline auto format_to_n(OutputIt out, size_t n, const S& format_str,
+                        const Args&... args) ->
+    typename std::enable_if<enable, format_to_n_result<OutputIt>>::type {
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  return vformat_to_n(out, n, to_string_view(format_str), vargs);
+}
+
+/**
+  Returns the number of characters in the output of
+  ``format(format_str, args...)``.
+ */
+template <typename... Args>
+inline size_t formatted_size(string_view format_str, Args&&... args) {
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  detail::counting_buffer<> buf;
+  detail::vformat_to(buf, format_str, vargs);
+  return buf.count();
 }
 
 template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vformat(
-    const S& format_str, basic_format_args<buffer_context<Char>> args) {
-  return internal::vformat(to_string_view(format_str), args);
+FMT_INLINE std::basic_string<Char> vformat(
+    const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  return detail::vformat(to_string_view(format_str), args);
 }
 
 /**
@@ -1470,47 +2071,51 @@
 // Pass char_t as a default template parameter instead of using
 // std::basic_string<char_t<S>> to reduce the symbol size.
 template <typename S, typename... Args, typename Char = char_t<S>>
-inline std::basic_string<Char> format(const S& format_str, Args&&... args) {
-  return internal::vformat(
-      to_string_view(format_str),
-      {internal::make_args_checked<Args...>(format_str, args...)});
+FMT_INLINE std::basic_string<Char> format(const S& format_str, Args&&... args) {
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  return detail::vformat(to_string_view(format_str), vargs);
 }
 
-FMT_API void vprint(std::FILE* f, string_view format_str, format_args args);
-FMT_API void vprint(string_view format_str, format_args args);
+FMT_API void vprint(string_view, format_args);
+FMT_API void vprint(std::FILE*, string_view, format_args);
 
 /**
   \rst
-  Prints formatted data to the file *f*. For wide format strings,
-  *f* should be in wide-oriented mode set via ``fwide(f, 1)`` or
-  ``_setmode(_fileno(f), _O_U8TEXT)`` on Windows.
+  Formats ``args`` according to specifications in ``format_str`` and writes the
+  output to the file ``f``. Strings are assumed to be Unicode-encoded unless the
+  ``FMT_UNICODE`` macro is set to 0.
 
   **Example**::
 
     fmt::print(stderr, "Don't {}!", "panic");
   \endrst
  */
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+template <typename S, typename... Args, typename Char = char_t<S>>
 inline void print(std::FILE* f, const S& format_str, Args&&... args) {
-  vprint(f, to_string_view(format_str),
-         internal::make_args_checked<Args...>(format_str, args...));
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  return detail::is_unicode<Char>()
+             ? vprint(f, to_string_view(format_str), vargs)
+             : detail::vprint_mojibake(f, to_string_view(format_str), vargs);
 }
 
 /**
   \rst
-  Prints formatted data to ``stdout``.
+  Formats ``args`` according to specifications in ``format_str`` and writes
+  the output to ``stdout``. Strings are assumed to be Unicode-encoded unless
+  the ``FMT_UNICODE`` macro is set to 0.
 
   **Example**::
 
     fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
   \endrst
  */
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+template <typename S, typename... Args, typename Char = char_t<S>>
 inline void print(const S& format_str, Args&&... args) {
-  vprint(to_string_view(format_str),
-         internal::make_args_checked<Args...>(format_str, args...));
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  return detail::is_unicode<Char>()
+             ? vprint(to_string_view(format_str), vargs)
+             : detail::vprint_mojibake(stdout, to_string_view(format_str),
+                                       vargs);
 }
 FMT_END_NAMESPACE
 
diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 72b3046..8f2fe73 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -8,56 +8,40 @@
 #ifndef FMT_FORMAT_INL_H_
 #define FMT_FORMAT_INL_H_
 
-#include "format.h"
-
 #include <cassert>
 #include <cctype>
 #include <climits>
 #include <cmath>
 #include <cstdarg>
-#include <cstring>  // for std::memmove
+#include <cstring>  // std::memmove
 #include <cwchar>
-#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+#include <exception>
+
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 #  include <locale>
 #endif
 
-#if FMT_USE_WINDOWS_H
-#  if !defined(FMT_HEADER_ONLY) && !defined(WIN32_LEAN_AND_MEAN)
-#    define WIN32_LEAN_AND_MEAN
-#  endif
-#  if defined(NOMINMAX) || defined(FMT_WIN_MINMAX)
-#    include <windows.h>
-#  else
-#    define NOMINMAX
-#    include <windows.h>
-#    undef NOMINMAX
-#  endif
+#ifdef _WIN32
+#  include <io.h>  // _isatty
 #endif
 
-#if FMT_EXCEPTIONS
-#  define FMT_TRY try
-#  define FMT_CATCH(x) catch (x)
-#else
-#  define FMT_TRY if (true)
-#  define FMT_CATCH(x) if (false)
-#endif
-
-#ifdef _MSC_VER
-#  pragma warning(push)
-#  pragma warning(disable : 4702)  // unreachable code
-#endif
+#include "format.h"
 
 // Dummy implementations of strerror_r and strerror_s called if corresponding
 // system functions are not available.
-inline fmt::internal::null<> strerror_r(int, char*, ...) { return {}; }
-inline fmt::internal::null<> strerror_s(char*, std::size_t, ...) { return {}; }
+inline fmt::detail::null<> strerror_r(int, char*, ...) { return {}; }
+inline fmt::detail::null<> strerror_s(char*, size_t, ...) { return {}; }
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
-  print(stderr, "{}:{}: assertion failed: {}", file, line, message);
-  std::abort();
+  // Use unchecked std::fprintf to avoid triggering another assertion when
+  // writing to stderr fails
+  std::fprintf(stderr, "%s:%d: assertion failed: %s", file, line, message);
+  // Chosen instead of std::abort to satisfy Clang in CUDA mode during device
+  // code pass.
+  std::terminate();
 }
 
 #ifndef _MSC_VER
@@ -73,8 +57,6 @@
 #  define FMT_SNPRINTF fmt_snprintf
 #endif  // _MSC_VER
 
-using format_func = void (*)(internal::buffer<char>&, int, string_view);
-
 // A portable thread-safe version of strerror.
 // Sets buffer to point to a string describing the error code.
 // This can be either a pointer to a string stored in buffer,
@@ -84,15 +66,15 @@
 //   ERANGE - buffer is not large enough to store the error message
 //   other  - failure
 // Buffer should be at least of size 1.
-FMT_FUNC int safe_strerror(int error_code, char*& buffer,
-                           std::size_t buffer_size) FMT_NOEXCEPT {
+inline int safe_strerror(int error_code, char*& buffer,
+                         size_t buffer_size) FMT_NOEXCEPT {
   FMT_ASSERT(buffer != nullptr && buffer_size != 0, "invalid buffer");
 
   class dispatcher {
    private:
     int error_code_;
     char*& buffer_;
-    std::size_t buffer_size_;
+    size_t buffer_size_;
 
     // A noop assignment operator to avoid bogus warnings.
     void operator=(const dispatcher&) {}
@@ -104,6 +86,7 @@
     }
 
     // Handle the result of GNU-specific version of strerror_r.
+    FMT_MAYBE_UNUSED
     int handle(char* message) {
       // If the buffer is full then the message is probably truncated.
       if (message == buffer_ && strlen(buffer_) == buffer_size_ - 1)
@@ -113,11 +96,13 @@
     }
 
     // Handle the case when strerror_r is not available.
-    int handle(internal::null<>) {
+    FMT_MAYBE_UNUSED
+    int handle(detail::null<>) {
       return fallback(strerror_s(buffer_, buffer_size_, error_code_));
     }
 
     // Fallback to strerror_s when strerror_r is not available.
+    FMT_MAYBE_UNUSED
     int fallback(int result) {
       // If the buffer is full then the message is probably truncated.
       return result == 0 && strlen(buffer_) == buffer_size_ - 1 ? ERANGE
@@ -126,7 +111,7 @@
 
 #if !FMT_MSC_VER
     // Fallback to strerror if strerror_r and strerror_s are not available.
-    int fallback(internal::null<>) {
+    int fallback(detail::null<>) {
       errno = 0;
       buffer_ = strerror(error_code_);
       return errno;
@@ -134,7 +119,7 @@
 #endif
 
    public:
-    dispatcher(int err_code, char*& buf, std::size_t buf_size)
+    dispatcher(int err_code, char*& buf, size_t buf_size)
         : error_code_(err_code), buffer_(buf), buffer_size_(buf_size) {}
 
     int run() { return handle(strerror_r(error_code_, buffer_, buffer_size_)); }
@@ -142,41 +127,29 @@
   return dispatcher(error_code, buffer, buffer_size).run();
 }
 
-FMT_FUNC void format_error_code(internal::buffer<char>& out, int error_code,
+FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
                                 string_view message) FMT_NOEXCEPT {
   // Report error code making sure that the output fits into
   // inline_buffer_size to avoid dynamic memory allocation and potential
   // bad_alloc.
-  out.resize(0);
+  out.try_resize(0);
   static const char SEP[] = ": ";
   static const char ERROR_STR[] = "error ";
   // Subtract 2 to account for terminating null characters in SEP and ERROR_STR.
-  std::size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
+  size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
   auto abs_value = static_cast<uint32_or_64_or_128_t<int>>(error_code);
-  if (internal::is_negative(error_code)) {
+  if (detail::is_negative(error_code)) {
     abs_value = 0 - abs_value;
     ++error_code_size;
   }
-  error_code_size += internal::to_unsigned(internal::count_digits(abs_value));
-  internal::writer w(out);
-  if (message.size() <= inline_buffer_size - error_code_size) {
-    w.write(message);
-    w.write(SEP);
-  }
-  w.write(ERROR_STR);
-  w.write(error_code);
+  error_code_size += detail::to_unsigned(detail::count_digits(abs_value));
+  auto it = buffer_appender<char>(out);
+  if (message.size() <= inline_buffer_size - error_code_size)
+    format_to(it, "{}{}", message, SEP);
+  format_to(it, "{}{}", ERROR_STR, error_code);
   assert(out.size() <= inline_buffer_size);
 }
 
-// A wrapper around fwrite that throws on error.
-FMT_FUNC void fwrite_fully(const void* ptr, size_t size, size_t count,
-                           FILE* stream) {
-  size_t written = std::fwrite(ptr, size, count, stream);
-  if (written < count) {
-    FMT_THROW(system_error(errno, "cannot write to file"));
-  }
-}
-
 FMT_FUNC void report_error(format_func func, int error_code,
                            string_view message) FMT_NOEXCEPT {
   memory_buffer full_message;
@@ -185,10 +158,17 @@
   (void)std::fwrite(full_message.data(), full_message.size(), 1, stderr);
   std::fputc('\n', stderr);
 }
-}  // namespace internal
+
+// A wrapper around fwrite that throws on error.
+inline void fwrite_fully(const void* ptr, size_t size, size_t count,
+                         FILE* stream) {
+  size_t written = std::fwrite(ptr, size, count, stream);
+  if (written < count) FMT_THROW(system_error(errno, "cannot write to file"));
+}
+}  // namespace detail
 
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-namespace internal {
+namespace detail {
 
 template <typename Locale>
 locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
@@ -211,18 +191,16 @@
   return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
       .decimal_point();
 }
-}  // namespace internal
+}  // namespace detail
 #else
 template <typename Char>
-FMT_FUNC std::string internal::grouping_impl(locale_ref) {
+FMT_FUNC std::string detail::grouping_impl(locale_ref) {
   return "\03";
 }
-template <typename Char>
-FMT_FUNC Char internal::thousands_sep_impl(locale_ref) {
+template <typename Char> FMT_FUNC Char detail::thousands_sep_impl(locale_ref) {
   return FMT_STATIC_THOUSANDS_SEPARATOR;
 }
-template <typename Char>
-FMT_FUNC Char internal::decimal_point_impl(locale_ref) {
+template <typename Char> FMT_FUNC Char detail::decimal_point_impl(locale_ref) {
   return '.';
 }
 #endif
@@ -239,9 +217,9 @@
   base = std::runtime_error(to_string(buffer));
 }
 
-namespace internal {
+namespace detail {
 
-template <> FMT_FUNC int count_digits<4>(internal::fallback_uintptr n) {
+template <> FMT_FUNC int count_digits<4>(detail::fallback_uintptr n) {
   // fallback_uintptr is always stored in little endian.
   int i = static_cast<int>(sizeof(void*)) - 1;
   while (i > 0 && n.value[i] == 0) --i;
@@ -250,12 +228,24 @@
 }
 
 template <typename T>
-const char basic_data<T>::digits[] =
-    "0001020304050607080910111213141516171819"
-    "2021222324252627282930313233343536373839"
-    "4041424344454647484950515253545556575859"
-    "6061626364656667686970717273747576777879"
-    "8081828384858687888990919293949596979899";
+const typename basic_data<T>::digit_pair basic_data<T>::digits[] = {
+    {'0', '0'}, {'0', '1'}, {'0', '2'}, {'0', '3'}, {'0', '4'}, {'0', '5'},
+    {'0', '6'}, {'0', '7'}, {'0', '8'}, {'0', '9'}, {'1', '0'}, {'1', '1'},
+    {'1', '2'}, {'1', '3'}, {'1', '4'}, {'1', '5'}, {'1', '6'}, {'1', '7'},
+    {'1', '8'}, {'1', '9'}, {'2', '0'}, {'2', '1'}, {'2', '2'}, {'2', '3'},
+    {'2', '4'}, {'2', '5'}, {'2', '6'}, {'2', '7'}, {'2', '8'}, {'2', '9'},
+    {'3', '0'}, {'3', '1'}, {'3', '2'}, {'3', '3'}, {'3', '4'}, {'3', '5'},
+    {'3', '6'}, {'3', '7'}, {'3', '8'}, {'3', '9'}, {'4', '0'}, {'4', '1'},
+    {'4', '2'}, {'4', '3'}, {'4', '4'}, {'4', '5'}, {'4', '6'}, {'4', '7'},
+    {'4', '8'}, {'4', '9'}, {'5', '0'}, {'5', '1'}, {'5', '2'}, {'5', '3'},
+    {'5', '4'}, {'5', '5'}, {'5', '6'}, {'5', '7'}, {'5', '8'}, {'5', '9'},
+    {'6', '0'}, {'6', '1'}, {'6', '2'}, {'6', '3'}, {'6', '4'}, {'6', '5'},
+    {'6', '6'}, {'6', '7'}, {'6', '8'}, {'6', '9'}, {'7', '0'}, {'7', '1'},
+    {'7', '2'}, {'7', '3'}, {'7', '4'}, {'7', '5'}, {'7', '6'}, {'7', '7'},
+    {'7', '8'}, {'7', '9'}, {'8', '0'}, {'8', '1'}, {'8', '2'}, {'8', '3'},
+    {'8', '4'}, {'8', '5'}, {'8', '6'}, {'8', '7'}, {'8', '8'}, {'8', '9'},
+    {'9', '0'}, {'9', '1'}, {'9', '2'}, {'9', '3'}, {'9', '4'}, {'9', '5'},
+    {'9', '6'}, {'9', '7'}, {'9', '8'}, {'9', '9'}};
 
 template <typename T>
 const char basic_data<T>::hex_digits[] = "0123456789abcdef";
@@ -273,16 +263,24 @@
 template <typename T>
 const uint32_t basic_data<T>::zero_or_powers_of_10_32[] = {0,
                                                            FMT_POWERS_OF_10(1)};
-
 template <typename T>
 const uint64_t basic_data<T>::zero_or_powers_of_10_64[] = {
     0, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
     10000000000000000000ULL};
 
+template <typename T>
+const uint32_t basic_data<T>::zero_or_powers_of_10_32_new[] = {
+    0, 0, FMT_POWERS_OF_10(1)};
+
+template <typename T>
+const uint64_t basic_data<T>::zero_or_powers_of_10_64_new[] = {
+    0, 0, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
+    10000000000000000000ULL};
+
 // Normalized 64-bit significands of pow(10, k), for k = -348, -340, ..., 340.
 // These are generated by support/compute-powers.py.
 template <typename T>
-const uint64_t basic_data<T>::pow10_significands[] = {
+const uint64_t basic_data<T>::grisu_pow10_significands[] = {
     0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76, 0x8b16fb203055ac76,
     0xcf42894a5dce35ea, 0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
     0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f, 0xbe5691ef416bd60c,
@@ -317,7 +315,7 @@
 // Binary exponents of pow(10, k), for k = -348, -340, ..., 340, corresponding
 // to significands above.
 template <typename T>
-const int16_t basic_data<T>::pow10_exponents[] = {
+const int16_t basic_data<T>::grisu_pow10_exponents[] = {
     -1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980, -954,
     -927,  -901,  -874,  -847,  -821,  -794,  -768,  -741,  -715,  -688, -661,
     -635,  -608,  -582,  -555,  -529,  -502,  -475,  -449,  -422,  -396, -369,
@@ -328,12 +326,754 @@
     827,   853,   880,   907,   933,   960,   986,   1013,  1039,  1066};
 
 template <typename T>
+const divtest_table_entry<uint32_t> basic_data<T>::divtest_table_for_pow5_32[] =
+    {{0x00000001, 0xffffffff}, {0xcccccccd, 0x33333333},
+     {0xc28f5c29, 0x0a3d70a3}, {0x26e978d5, 0x020c49ba},
+     {0x3afb7e91, 0x0068db8b}, {0x0bcbe61d, 0x0014f8b5},
+     {0x68c26139, 0x000431bd}, {0xae8d46a5, 0x0000d6bf},
+     {0x22e90e21, 0x00002af3}, {0x3a2e9c6d, 0x00000897},
+     {0x3ed61f49, 0x000001b7}};
+
+template <typename T>
+const divtest_table_entry<uint64_t> basic_data<T>::divtest_table_for_pow5_64[] =
+    {{0x0000000000000001, 0xffffffffffffffff},
+     {0xcccccccccccccccd, 0x3333333333333333},
+     {0x8f5c28f5c28f5c29, 0x0a3d70a3d70a3d70},
+     {0x1cac083126e978d5, 0x020c49ba5e353f7c},
+     {0xd288ce703afb7e91, 0x0068db8bac710cb2},
+     {0x5d4e8fb00bcbe61d, 0x0014f8b588e368f0},
+     {0x790fb65668c26139, 0x000431bde82d7b63},
+     {0xe5032477ae8d46a5, 0x0000d6bf94d5e57a},
+     {0xc767074b22e90e21, 0x00002af31dc46118},
+     {0x8e47ce423a2e9c6d, 0x0000089705f4136b},
+     {0x4fa7f60d3ed61f49, 0x000001b7cdfd9d7b},
+     {0x0fee64690c913975, 0x00000057f5ff85e5},
+     {0x3662e0e1cf503eb1, 0x000000119799812d},
+     {0xa47a2cf9f6433fbd, 0x0000000384b84d09},
+     {0x54186f653140a659, 0x00000000b424dc35},
+     {0x7738164770402145, 0x0000000024075f3d},
+     {0xe4a4d1417cd9a041, 0x000000000734aca5},
+     {0xc75429d9e5c5200d, 0x000000000170ef54},
+     {0xc1773b91fac10669, 0x000000000049c977},
+     {0x26b172506559ce15, 0x00000000000ec1e4},
+     {0xd489e3a9addec2d1, 0x000000000002f394},
+     {0x90e860bb892c8d5d, 0x000000000000971d},
+     {0x502e79bf1b6f4f79, 0x0000000000001e39},
+     {0xdcd618596be30fe5, 0x000000000000060b}};
+
+template <typename T>
+const uint64_t basic_data<T>::dragonbox_pow10_significands_64[] = {
+    0x81ceb32c4b43fcf5, 0xa2425ff75e14fc32, 0xcad2f7f5359a3b3f,
+    0xfd87b5f28300ca0e, 0x9e74d1b791e07e49, 0xc612062576589ddb,
+    0xf79687aed3eec552, 0x9abe14cd44753b53, 0xc16d9a0095928a28,
+    0xf1c90080baf72cb2, 0x971da05074da7bef, 0xbce5086492111aeb,
+    0xec1e4a7db69561a6, 0x9392ee8e921d5d08, 0xb877aa3236a4b44a,
+    0xe69594bec44de15c, 0x901d7cf73ab0acda, 0xb424dc35095cd810,
+    0xe12e13424bb40e14, 0x8cbccc096f5088cc, 0xafebff0bcb24aaff,
+    0xdbe6fecebdedd5bf, 0x89705f4136b4a598, 0xabcc77118461cefd,
+    0xd6bf94d5e57a42bd, 0x8637bd05af6c69b6, 0xa7c5ac471b478424,
+    0xd1b71758e219652c, 0x83126e978d4fdf3c, 0xa3d70a3d70a3d70b,
+    0xcccccccccccccccd, 0x8000000000000000, 0xa000000000000000,
+    0xc800000000000000, 0xfa00000000000000, 0x9c40000000000000,
+    0xc350000000000000, 0xf424000000000000, 0x9896800000000000,
+    0xbebc200000000000, 0xee6b280000000000, 0x9502f90000000000,
+    0xba43b74000000000, 0xe8d4a51000000000, 0x9184e72a00000000,
+    0xb5e620f480000000, 0xe35fa931a0000000, 0x8e1bc9bf04000000,
+    0xb1a2bc2ec5000000, 0xde0b6b3a76400000, 0x8ac7230489e80000,
+    0xad78ebc5ac620000, 0xd8d726b7177a8000, 0x878678326eac9000,
+    0xa968163f0a57b400, 0xd3c21bcecceda100, 0x84595161401484a0,
+    0xa56fa5b99019a5c8, 0xcecb8f27f4200f3a, 0x813f3978f8940984,
+    0xa18f07d736b90be5, 0xc9f2c9cd04674ede, 0xfc6f7c4045812296,
+    0x9dc5ada82b70b59d, 0xc5371912364ce305, 0xf684df56c3e01bc6,
+    0x9a130b963a6c115c, 0xc097ce7bc90715b3, 0xf0bdc21abb48db20,
+    0x96769950b50d88f4, 0xbc143fa4e250eb31, 0xeb194f8e1ae525fd,
+    0x92efd1b8d0cf37be, 0xb7abc627050305ad, 0xe596b7b0c643c719,
+    0x8f7e32ce7bea5c6f, 0xb35dbf821ae4f38b, 0xe0352f62a19e306e};
+
+template <typename T>
+const uint128_wrapper basic_data<T>::dragonbox_pow10_significands_128[] = {
+#if FMT_USE_FULL_CACHE_DRAGONBOX
+    {0xff77b1fcbebcdc4f, 0x25e8e89c13bb0f7b},
+    {0x9faacf3df73609b1, 0x77b191618c54e9ad},
+    {0xc795830d75038c1d, 0xd59df5b9ef6a2418},
+    {0xf97ae3d0d2446f25, 0x4b0573286b44ad1e},
+    {0x9becce62836ac577, 0x4ee367f9430aec33},
+    {0xc2e801fb244576d5, 0x229c41f793cda740},
+    {0xf3a20279ed56d48a, 0x6b43527578c11110},
+    {0x9845418c345644d6, 0x830a13896b78aaaa},
+    {0xbe5691ef416bd60c, 0x23cc986bc656d554},
+    {0xedec366b11c6cb8f, 0x2cbfbe86b7ec8aa9},
+    {0x94b3a202eb1c3f39, 0x7bf7d71432f3d6aa},
+    {0xb9e08a83a5e34f07, 0xdaf5ccd93fb0cc54},
+    {0xe858ad248f5c22c9, 0xd1b3400f8f9cff69},
+    {0x91376c36d99995be, 0x23100809b9c21fa2},
+    {0xb58547448ffffb2d, 0xabd40a0c2832a78b},
+    {0xe2e69915b3fff9f9, 0x16c90c8f323f516d},
+    {0x8dd01fad907ffc3b, 0xae3da7d97f6792e4},
+    {0xb1442798f49ffb4a, 0x99cd11cfdf41779d},
+    {0xdd95317f31c7fa1d, 0x40405643d711d584},
+    {0x8a7d3eef7f1cfc52, 0x482835ea666b2573},
+    {0xad1c8eab5ee43b66, 0xda3243650005eed0},
+    {0xd863b256369d4a40, 0x90bed43e40076a83},
+    {0x873e4f75e2224e68, 0x5a7744a6e804a292},
+    {0xa90de3535aaae202, 0x711515d0a205cb37},
+    {0xd3515c2831559a83, 0x0d5a5b44ca873e04},
+    {0x8412d9991ed58091, 0xe858790afe9486c3},
+    {0xa5178fff668ae0b6, 0x626e974dbe39a873},
+    {0xce5d73ff402d98e3, 0xfb0a3d212dc81290},
+    {0x80fa687f881c7f8e, 0x7ce66634bc9d0b9a},
+    {0xa139029f6a239f72, 0x1c1fffc1ebc44e81},
+    {0xc987434744ac874e, 0xa327ffb266b56221},
+    {0xfbe9141915d7a922, 0x4bf1ff9f0062baa9},
+    {0x9d71ac8fada6c9b5, 0x6f773fc3603db4aa},
+    {0xc4ce17b399107c22, 0xcb550fb4384d21d4},
+    {0xf6019da07f549b2b, 0x7e2a53a146606a49},
+    {0x99c102844f94e0fb, 0x2eda7444cbfc426e},
+    {0xc0314325637a1939, 0xfa911155fefb5309},
+    {0xf03d93eebc589f88, 0x793555ab7eba27cb},
+    {0x96267c7535b763b5, 0x4bc1558b2f3458df},
+    {0xbbb01b9283253ca2, 0x9eb1aaedfb016f17},
+    {0xea9c227723ee8bcb, 0x465e15a979c1cadd},
+    {0x92a1958a7675175f, 0x0bfacd89ec191eca},
+    {0xb749faed14125d36, 0xcef980ec671f667c},
+    {0xe51c79a85916f484, 0x82b7e12780e7401b},
+    {0x8f31cc0937ae58d2, 0xd1b2ecb8b0908811},
+    {0xb2fe3f0b8599ef07, 0x861fa7e6dcb4aa16},
+    {0xdfbdcece67006ac9, 0x67a791e093e1d49b},
+    {0x8bd6a141006042bd, 0xe0c8bb2c5c6d24e1},
+    {0xaecc49914078536d, 0x58fae9f773886e19},
+    {0xda7f5bf590966848, 0xaf39a475506a899f},
+    {0x888f99797a5e012d, 0x6d8406c952429604},
+    {0xaab37fd7d8f58178, 0xc8e5087ba6d33b84},
+    {0xd5605fcdcf32e1d6, 0xfb1e4a9a90880a65},
+    {0x855c3be0a17fcd26, 0x5cf2eea09a550680},
+    {0xa6b34ad8c9dfc06f, 0xf42faa48c0ea481f},
+    {0xd0601d8efc57b08b, 0xf13b94daf124da27},
+    {0x823c12795db6ce57, 0x76c53d08d6b70859},
+    {0xa2cb1717b52481ed, 0x54768c4b0c64ca6f},
+    {0xcb7ddcdda26da268, 0xa9942f5dcf7dfd0a},
+    {0xfe5d54150b090b02, 0xd3f93b35435d7c4d},
+    {0x9efa548d26e5a6e1, 0xc47bc5014a1a6db0},
+    {0xc6b8e9b0709f109a, 0x359ab6419ca1091c},
+    {0xf867241c8cc6d4c0, 0xc30163d203c94b63},
+    {0x9b407691d7fc44f8, 0x79e0de63425dcf1e},
+    {0xc21094364dfb5636, 0x985915fc12f542e5},
+    {0xf294b943e17a2bc4, 0x3e6f5b7b17b2939e},
+    {0x979cf3ca6cec5b5a, 0xa705992ceecf9c43},
+    {0xbd8430bd08277231, 0x50c6ff782a838354},
+    {0xece53cec4a314ebd, 0xa4f8bf5635246429},
+    {0x940f4613ae5ed136, 0x871b7795e136be9a},
+    {0xb913179899f68584, 0x28e2557b59846e40},
+    {0xe757dd7ec07426e5, 0x331aeada2fe589d0},
+    {0x9096ea6f3848984f, 0x3ff0d2c85def7622},
+    {0xb4bca50b065abe63, 0x0fed077a756b53aa},
+    {0xe1ebce4dc7f16dfb, 0xd3e8495912c62895},
+    {0x8d3360f09cf6e4bd, 0x64712dd7abbbd95d},
+    {0xb080392cc4349dec, 0xbd8d794d96aacfb4},
+    {0xdca04777f541c567, 0xecf0d7a0fc5583a1},
+    {0x89e42caaf9491b60, 0xf41686c49db57245},
+    {0xac5d37d5b79b6239, 0x311c2875c522ced6},
+    {0xd77485cb25823ac7, 0x7d633293366b828c},
+    {0x86a8d39ef77164bc, 0xae5dff9c02033198},
+    {0xa8530886b54dbdeb, 0xd9f57f830283fdfd},
+    {0xd267caa862a12d66, 0xd072df63c324fd7c},
+    {0x8380dea93da4bc60, 0x4247cb9e59f71e6e},
+    {0xa46116538d0deb78, 0x52d9be85f074e609},
+    {0xcd795be870516656, 0x67902e276c921f8c},
+    {0x806bd9714632dff6, 0x00ba1cd8a3db53b7},
+    {0xa086cfcd97bf97f3, 0x80e8a40eccd228a5},
+    {0xc8a883c0fdaf7df0, 0x6122cd128006b2ce},
+    {0xfad2a4b13d1b5d6c, 0x796b805720085f82},
+    {0x9cc3a6eec6311a63, 0xcbe3303674053bb1},
+    {0xc3f490aa77bd60fc, 0xbedbfc4411068a9d},
+    {0xf4f1b4d515acb93b, 0xee92fb5515482d45},
+    {0x991711052d8bf3c5, 0x751bdd152d4d1c4b},
+    {0xbf5cd54678eef0b6, 0xd262d45a78a0635e},
+    {0xef340a98172aace4, 0x86fb897116c87c35},
+    {0x9580869f0e7aac0e, 0xd45d35e6ae3d4da1},
+    {0xbae0a846d2195712, 0x8974836059cca10a},
+    {0xe998d258869facd7, 0x2bd1a438703fc94c},
+    {0x91ff83775423cc06, 0x7b6306a34627ddd0},
+    {0xb67f6455292cbf08, 0x1a3bc84c17b1d543},
+    {0xe41f3d6a7377eeca, 0x20caba5f1d9e4a94},
+    {0x8e938662882af53e, 0x547eb47b7282ee9d},
+    {0xb23867fb2a35b28d, 0xe99e619a4f23aa44},
+    {0xdec681f9f4c31f31, 0x6405fa00e2ec94d5},
+    {0x8b3c113c38f9f37e, 0xde83bc408dd3dd05},
+    {0xae0b158b4738705e, 0x9624ab50b148d446},
+    {0xd98ddaee19068c76, 0x3badd624dd9b0958},
+    {0x87f8a8d4cfa417c9, 0xe54ca5d70a80e5d7},
+    {0xa9f6d30a038d1dbc, 0x5e9fcf4ccd211f4d},
+    {0xd47487cc8470652b, 0x7647c32000696720},
+    {0x84c8d4dfd2c63f3b, 0x29ecd9f40041e074},
+    {0xa5fb0a17c777cf09, 0xf468107100525891},
+    {0xcf79cc9db955c2cc, 0x7182148d4066eeb5},
+    {0x81ac1fe293d599bf, 0xc6f14cd848405531},
+    {0xa21727db38cb002f, 0xb8ada00e5a506a7d},
+    {0xca9cf1d206fdc03b, 0xa6d90811f0e4851d},
+    {0xfd442e4688bd304a, 0x908f4a166d1da664},
+    {0x9e4a9cec15763e2e, 0x9a598e4e043287ff},
+    {0xc5dd44271ad3cdba, 0x40eff1e1853f29fe},
+    {0xf7549530e188c128, 0xd12bee59e68ef47d},
+    {0x9a94dd3e8cf578b9, 0x82bb74f8301958cf},
+    {0xc13a148e3032d6e7, 0xe36a52363c1faf02},
+    {0xf18899b1bc3f8ca1, 0xdc44e6c3cb279ac2},
+    {0x96f5600f15a7b7e5, 0x29ab103a5ef8c0ba},
+    {0xbcb2b812db11a5de, 0x7415d448f6b6f0e8},
+    {0xebdf661791d60f56, 0x111b495b3464ad22},
+    {0x936b9fcebb25c995, 0xcab10dd900beec35},
+    {0xb84687c269ef3bfb, 0x3d5d514f40eea743},
+    {0xe65829b3046b0afa, 0x0cb4a5a3112a5113},
+    {0x8ff71a0fe2c2e6dc, 0x47f0e785eaba72ac},
+    {0xb3f4e093db73a093, 0x59ed216765690f57},
+    {0xe0f218b8d25088b8, 0x306869c13ec3532d},
+    {0x8c974f7383725573, 0x1e414218c73a13fc},
+    {0xafbd2350644eeacf, 0xe5d1929ef90898fb},
+    {0xdbac6c247d62a583, 0xdf45f746b74abf3a},
+    {0x894bc396ce5da772, 0x6b8bba8c328eb784},
+    {0xab9eb47c81f5114f, 0x066ea92f3f326565},
+    {0xd686619ba27255a2, 0xc80a537b0efefebe},
+    {0x8613fd0145877585, 0xbd06742ce95f5f37},
+    {0xa798fc4196e952e7, 0x2c48113823b73705},
+    {0xd17f3b51fca3a7a0, 0xf75a15862ca504c6},
+    {0x82ef85133de648c4, 0x9a984d73dbe722fc},
+    {0xa3ab66580d5fdaf5, 0xc13e60d0d2e0ebbb},
+    {0xcc963fee10b7d1b3, 0x318df905079926a9},
+    {0xffbbcfe994e5c61f, 0xfdf17746497f7053},
+    {0x9fd561f1fd0f9bd3, 0xfeb6ea8bedefa634},
+    {0xc7caba6e7c5382c8, 0xfe64a52ee96b8fc1},
+    {0xf9bd690a1b68637b, 0x3dfdce7aa3c673b1},
+    {0x9c1661a651213e2d, 0x06bea10ca65c084f},
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+    {0x8335616aed761f1f, 0x7f44e6bd49e807b8},
+    {0xa402b9c5a8d3a6e7, 0x5f16206c9c6209a6},
+    {0xcd036837130890a1, 0x36dba887c37a8c0f},
+    {0x802221226be55a64, 0xc2494954da2c9789},
+    {0xa02aa96b06deb0fd, 0xf2db9baa10b7bd6c},
+    {0xc83553c5c8965d3d, 0x6f92829494e5acc7},
+    {0xfa42a8b73abbf48c, 0xcb772339ba1f17f9},
+    {0x9c69a97284b578d7, 0xff2a760414536efb},
+    {0xc38413cf25e2d70d, 0xfef5138519684aba},
+    {0xf46518c2ef5b8cd1, 0x7eb258665fc25d69},
+    {0x98bf2f79d5993802, 0xef2f773ffbd97a61},
+    {0xbeeefb584aff8603, 0xaafb550ffacfd8fa},
+    {0xeeaaba2e5dbf6784, 0x95ba2a53f983cf38},
+    {0x952ab45cfa97a0b2, 0xdd945a747bf26183},
+    {0xba756174393d88df, 0x94f971119aeef9e4},
+    {0xe912b9d1478ceb17, 0x7a37cd5601aab85d},
+    {0x91abb422ccb812ee, 0xac62e055c10ab33a},
+    {0xb616a12b7fe617aa, 0x577b986b314d6009},
+    {0xe39c49765fdf9d94, 0xed5a7e85fda0b80b},
+    {0x8e41ade9fbebc27d, 0x14588f13be847307},
+    {0xb1d219647ae6b31c, 0x596eb2d8ae258fc8},
+    {0xde469fbd99a05fe3, 0x6fca5f8ed9aef3bb},
+    {0x8aec23d680043bee, 0x25de7bb9480d5854},
+    {0xada72ccc20054ae9, 0xaf561aa79a10ae6a},
+    {0xd910f7ff28069da4, 0x1b2ba1518094da04},
+    {0x87aa9aff79042286, 0x90fb44d2f05d0842},
+    {0xa99541bf57452b28, 0x353a1607ac744a53},
+    {0xd3fa922f2d1675f2, 0x42889b8997915ce8},
+    {0x847c9b5d7c2e09b7, 0x69956135febada11},
+    {0xa59bc234db398c25, 0x43fab9837e699095},
+    {0xcf02b2c21207ef2e, 0x94f967e45e03f4bb},
+    {0x8161afb94b44f57d, 0x1d1be0eebac278f5},
+    {0xa1ba1ba79e1632dc, 0x6462d92a69731732},
+    {0xca28a291859bbf93, 0x7d7b8f7503cfdcfe},
+    {0xfcb2cb35e702af78, 0x5cda735244c3d43e},
+    {0x9defbf01b061adab, 0x3a0888136afa64a7},
+    {0xc56baec21c7a1916, 0x088aaa1845b8fdd0},
+    {0xf6c69a72a3989f5b, 0x8aad549e57273d45},
+    {0x9a3c2087a63f6399, 0x36ac54e2f678864b},
+    {0xc0cb28a98fcf3c7f, 0x84576a1bb416a7dd},
+    {0xf0fdf2d3f3c30b9f, 0x656d44a2a11c51d5},
+    {0x969eb7c47859e743, 0x9f644ae5a4b1b325},
+    {0xbc4665b596706114, 0x873d5d9f0dde1fee},
+    {0xeb57ff22fc0c7959, 0xa90cb506d155a7ea},
+    {0x9316ff75dd87cbd8, 0x09a7f12442d588f2},
+    {0xb7dcbf5354e9bece, 0x0c11ed6d538aeb2f},
+    {0xe5d3ef282a242e81, 0x8f1668c8a86da5fa},
+    {0x8fa475791a569d10, 0xf96e017d694487bc},
+    {0xb38d92d760ec4455, 0x37c981dcc395a9ac},
+    {0xe070f78d3927556a, 0x85bbe253f47b1417},
+    {0x8c469ab843b89562, 0x93956d7478ccec8e},
+    {0xaf58416654a6babb, 0x387ac8d1970027b2},
+    {0xdb2e51bfe9d0696a, 0x06997b05fcc0319e},
+    {0x88fcf317f22241e2, 0x441fece3bdf81f03},
+    {0xab3c2fddeeaad25a, 0xd527e81cad7626c3},
+    {0xd60b3bd56a5586f1, 0x8a71e223d8d3b074},
+    {0x85c7056562757456, 0xf6872d5667844e49},
+    {0xa738c6bebb12d16c, 0xb428f8ac016561db},
+    {0xd106f86e69d785c7, 0xe13336d701beba52},
+    {0x82a45b450226b39c, 0xecc0024661173473},
+    {0xa34d721642b06084, 0x27f002d7f95d0190},
+    {0xcc20ce9bd35c78a5, 0x31ec038df7b441f4},
+    {0xff290242c83396ce, 0x7e67047175a15271},
+    {0x9f79a169bd203e41, 0x0f0062c6e984d386},
+    {0xc75809c42c684dd1, 0x52c07b78a3e60868},
+    {0xf92e0c3537826145, 0xa7709a56ccdf8a82},
+    {0x9bbcc7a142b17ccb, 0x88a66076400bb691},
+    {0xc2abf989935ddbfe, 0x6acff893d00ea435},
+    {0xf356f7ebf83552fe, 0x0583f6b8c4124d43},
+    {0x98165af37b2153de, 0xc3727a337a8b704a},
+    {0xbe1bf1b059e9a8d6, 0x744f18c0592e4c5c},
+    {0xeda2ee1c7064130c, 0x1162def06f79df73},
+    {0x9485d4d1c63e8be7, 0x8addcb5645ac2ba8},
+    {0xb9a74a0637ce2ee1, 0x6d953e2bd7173692},
+    {0xe8111c87c5c1ba99, 0xc8fa8db6ccdd0437},
+    {0x910ab1d4db9914a0, 0x1d9c9892400a22a2},
+    {0xb54d5e4a127f59c8, 0x2503beb6d00cab4b},
+    {0xe2a0b5dc971f303a, 0x2e44ae64840fd61d},
+    {0x8da471a9de737e24, 0x5ceaecfed289e5d2},
+    {0xb10d8e1456105dad, 0x7425a83e872c5f47},
+    {0xdd50f1996b947518, 0xd12f124e28f77719},
+    {0x8a5296ffe33cc92f, 0x82bd6b70d99aaa6f},
+    {0xace73cbfdc0bfb7b, 0x636cc64d1001550b},
+    {0xd8210befd30efa5a, 0x3c47f7e05401aa4e},
+    {0x8714a775e3e95c78, 0x65acfaec34810a71},
+    {0xa8d9d1535ce3b396, 0x7f1839a741a14d0d},
+    {0xd31045a8341ca07c, 0x1ede48111209a050},
+    {0x83ea2b892091e44d, 0x934aed0aab460432},
+    {0xa4e4b66b68b65d60, 0xf81da84d5617853f},
+    {0xce1de40642e3f4b9, 0x36251260ab9d668e},
+    {0x80d2ae83e9ce78f3, 0xc1d72b7c6b426019},
+    {0xa1075a24e4421730, 0xb24cf65b8612f81f},
+    {0xc94930ae1d529cfc, 0xdee033f26797b627},
+    {0xfb9b7cd9a4a7443c, 0x169840ef017da3b1},
+    {0x9d412e0806e88aa5, 0x8e1f289560ee864e},
+    {0xc491798a08a2ad4e, 0xf1a6f2bab92a27e2},
+    {0xf5b5d7ec8acb58a2, 0xae10af696774b1db},
+    {0x9991a6f3d6bf1765, 0xacca6da1e0a8ef29},
+    {0xbff610b0cc6edd3f, 0x17fd090a58d32af3},
+    {0xeff394dcff8a948e, 0xddfc4b4cef07f5b0},
+    {0x95f83d0a1fb69cd9, 0x4abdaf101564f98e},
+    {0xbb764c4ca7a4440f, 0x9d6d1ad41abe37f1},
+    {0xea53df5fd18d5513, 0x84c86189216dc5ed},
+    {0x92746b9be2f8552c, 0x32fd3cf5b4e49bb4},
+    {0xb7118682dbb66a77, 0x3fbc8c33221dc2a1},
+    {0xe4d5e82392a40515, 0x0fabaf3feaa5334a},
+    {0x8f05b1163ba6832d, 0x29cb4d87f2a7400e},
+    {0xb2c71d5bca9023f8, 0x743e20e9ef511012},
+    {0xdf78e4b2bd342cf6, 0x914da9246b255416},
+    {0x8bab8eefb6409c1a, 0x1ad089b6c2f7548e},
+    {0xae9672aba3d0c320, 0xa184ac2473b529b1},
+    {0xda3c0f568cc4f3e8, 0xc9e5d72d90a2741e},
+    {0x8865899617fb1871, 0x7e2fa67c7a658892},
+    {0xaa7eebfb9df9de8d, 0xddbb901b98feeab7},
+    {0xd51ea6fa85785631, 0x552a74227f3ea565},
+    {0x8533285c936b35de, 0xd53a88958f87275f},
+    {0xa67ff273b8460356, 0x8a892abaf368f137},
+    {0xd01fef10a657842c, 0x2d2b7569b0432d85},
+    {0x8213f56a67f6b29b, 0x9c3b29620e29fc73},
+    {0xa298f2c501f45f42, 0x8349f3ba91b47b8f},
+    {0xcb3f2f7642717713, 0x241c70a936219a73},
+    {0xfe0efb53d30dd4d7, 0xed238cd383aa0110},
+    {0x9ec95d1463e8a506, 0xf4363804324a40aa},
+    {0xc67bb4597ce2ce48, 0xb143c6053edcd0d5},
+    {0xf81aa16fdc1b81da, 0xdd94b7868e94050a},
+    {0x9b10a4e5e9913128, 0xca7cf2b4191c8326},
+    {0xc1d4ce1f63f57d72, 0xfd1c2f611f63a3f0},
+    {0xf24a01a73cf2dccf, 0xbc633b39673c8cec},
+    {0x976e41088617ca01, 0xd5be0503e085d813},
+    {0xbd49d14aa79dbc82, 0x4b2d8644d8a74e18},
+    {0xec9c459d51852ba2, 0xddf8e7d60ed1219e},
+    {0x93e1ab8252f33b45, 0xcabb90e5c942b503},
+    {0xb8da1662e7b00a17, 0x3d6a751f3b936243},
+    {0xe7109bfba19c0c9d, 0x0cc512670a783ad4},
+    {0x906a617d450187e2, 0x27fb2b80668b24c5},
+    {0xb484f9dc9641e9da, 0xb1f9f660802dedf6},
+    {0xe1a63853bbd26451, 0x5e7873f8a0396973},
+    {0x8d07e33455637eb2, 0xdb0b487b6423e1e8},
+    {0xb049dc016abc5e5f, 0x91ce1a9a3d2cda62},
+    {0xdc5c5301c56b75f7, 0x7641a140cc7810fb},
+    {0x89b9b3e11b6329ba, 0xa9e904c87fcb0a9d},
+    {0xac2820d9623bf429, 0x546345fa9fbdcd44},
+    {0xd732290fbacaf133, 0xa97c177947ad4095},
+    {0x867f59a9d4bed6c0, 0x49ed8eabcccc485d},
+    {0xa81f301449ee8c70, 0x5c68f256bfff5a74},
+    {0xd226fc195c6a2f8c, 0x73832eec6fff3111},
+    {0x83585d8fd9c25db7, 0xc831fd53c5ff7eab},
+    {0xa42e74f3d032f525, 0xba3e7ca8b77f5e55},
+    {0xcd3a1230c43fb26f, 0x28ce1bd2e55f35eb},
+    {0x80444b5e7aa7cf85, 0x7980d163cf5b81b3},
+    {0xa0555e361951c366, 0xd7e105bcc332621f},
+    {0xc86ab5c39fa63440, 0x8dd9472bf3fefaa7},
+    {0xfa856334878fc150, 0xb14f98f6f0feb951},
+    {0x9c935e00d4b9d8d2, 0x6ed1bf9a569f33d3},
+    {0xc3b8358109e84f07, 0x0a862f80ec4700c8},
+    {0xf4a642e14c6262c8, 0xcd27bb612758c0fa},
+    {0x98e7e9cccfbd7dbd, 0x8038d51cb897789c},
+    {0xbf21e44003acdd2c, 0xe0470a63e6bd56c3},
+    {0xeeea5d5004981478, 0x1858ccfce06cac74},
+    {0x95527a5202df0ccb, 0x0f37801e0c43ebc8},
+    {0xbaa718e68396cffd, 0xd30560258f54e6ba},
+    {0xe950df20247c83fd, 0x47c6b82ef32a2069},
+    {0x91d28b7416cdd27e, 0x4cdc331d57fa5441},
+    {0xb6472e511c81471d, 0xe0133fe4adf8e952},
+    {0xe3d8f9e563a198e5, 0x58180fddd97723a6},
+    {0x8e679c2f5e44ff8f, 0x570f09eaa7ea7648},
+    {0xb201833b35d63f73, 0x2cd2cc6551e513da},
+    {0xde81e40a034bcf4f, 0xf8077f7ea65e58d1},
+    {0x8b112e86420f6191, 0xfb04afaf27faf782},
+    {0xadd57a27d29339f6, 0x79c5db9af1f9b563},
+    {0xd94ad8b1c7380874, 0x18375281ae7822bc},
+    {0x87cec76f1c830548, 0x8f2293910d0b15b5},
+    {0xa9c2794ae3a3c69a, 0xb2eb3875504ddb22},
+    {0xd433179d9c8cb841, 0x5fa60692a46151eb},
+    {0x849feec281d7f328, 0xdbc7c41ba6bcd333},
+    {0xa5c7ea73224deff3, 0x12b9b522906c0800},
+    {0xcf39e50feae16bef, 0xd768226b34870a00},
+    {0x81842f29f2cce375, 0xe6a1158300d46640},
+    {0xa1e53af46f801c53, 0x60495ae3c1097fd0},
+    {0xca5e89b18b602368, 0x385bb19cb14bdfc4},
+    {0xfcf62c1dee382c42, 0x46729e03dd9ed7b5},
+    {0x9e19db92b4e31ba9, 0x6c07a2c26a8346d1},
+    {0xc5a05277621be293, 0xc7098b7305241885},
+    {0xf70867153aa2db38, 0xb8cbee4fc66d1ea7}
+#else
+    {0xff77b1fcbebcdc4f, 0x25e8e89c13bb0f7b},
+    {0xce5d73ff402d98e3, 0xfb0a3d212dc81290},
+    {0xa6b34ad8c9dfc06f, 0xf42faa48c0ea481f},
+    {0x86a8d39ef77164bc, 0xae5dff9c02033198},
+    {0xd98ddaee19068c76, 0x3badd624dd9b0958},
+    {0xafbd2350644eeacf, 0xe5d1929ef90898fb},
+    {0x8df5efabc5979c8f, 0xca8d3ffa1ef463c2},
+    {0xe55990879ddcaabd, 0xcc420a6a101d0516},
+    {0xb94470938fa89bce, 0xf808e40e8d5b3e6a},
+    {0x95a8637627989aad, 0xdde7001379a44aa9},
+    {0xf1c90080baf72cb1, 0x5324c68b12dd6339},
+    {0xc350000000000000, 0x0000000000000000},
+    {0x9dc5ada82b70b59d, 0xf020000000000000},
+    {0xfee50b7025c36a08, 0x02f236d04753d5b4},
+    {0xcde6fd5e09abcf26, 0xed4c0226b55e6f86},
+    {0xa6539930bf6bff45, 0x84db8346b786151c},
+    {0x865b86925b9bc5c2, 0x0b8a2392ba45a9b2},
+    {0xd910f7ff28069da4, 0x1b2ba1518094da04},
+    {0xaf58416654a6babb, 0x387ac8d1970027b2},
+    {0x8da471a9de737e24, 0x5ceaecfed289e5d2},
+    {0xe4d5e82392a40515, 0x0fabaf3feaa5334a},
+    {0xb8da1662e7b00a17, 0x3d6a751f3b936243},
+    {0x95527a5202df0ccb, 0x0f37801e0c43ebc8}
+#endif
+};
+
+#if !FMT_USE_FULL_CACHE_DRAGONBOX
+template <typename T>
+const uint64_t basic_data<T>::powers_of_5_64[] = {
+    0x0000000000000001, 0x0000000000000005, 0x0000000000000019,
+    0x000000000000007d, 0x0000000000000271, 0x0000000000000c35,
+    0x0000000000003d09, 0x000000000001312d, 0x000000000005f5e1,
+    0x00000000001dcd65, 0x00000000009502f9, 0x0000000002e90edd,
+    0x000000000e8d4a51, 0x0000000048c27395, 0x000000016bcc41e9,
+    0x000000071afd498d, 0x0000002386f26fc1, 0x000000b1a2bc2ec5,
+    0x000003782dace9d9, 0x00001158e460913d, 0x000056bc75e2d631,
+    0x0001b1ae4d6e2ef5, 0x000878678326eac9, 0x002a5a058fc295ed,
+    0x00d3c21bcecceda1, 0x0422ca8b0a00a425, 0x14adf4b7320334b9};
+
+template <typename T>
+const uint32_t basic_data<T>::dragonbox_pow10_recovery_errors[] = {
+    0x50001400, 0x54044100, 0x54014555, 0x55954415, 0x54115555, 0x00000001,
+    0x50000000, 0x00104000, 0x54010004, 0x05004001, 0x55555544, 0x41545555,
+    0x54040551, 0x15445545, 0x51555514, 0x10000015, 0x00101100, 0x01100015,
+    0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x04450514, 0x45414110,
+    0x55555145, 0x50544050, 0x15040155, 0x11054140, 0x50111514, 0x11451454,
+    0x00400541, 0x00000000, 0x55555450, 0x10056551, 0x10054011, 0x55551014,
+    0x69514555, 0x05151109, 0x00155555};
+#endif
+
+template <typename T>
 const char basic_data<T>::foreground_color[] = "\x1b[38;2;";
 template <typename T>
 const char basic_data<T>::background_color[] = "\x1b[48;2;";
 template <typename T> const char basic_data<T>::reset_color[] = "\x1b[0m";
 template <typename T> const wchar_t basic_data<T>::wreset_color[] = L"\x1b[0m";
 template <typename T> const char basic_data<T>::signs[] = {0, '-', '+', ' '};
+template <typename T>
+const char basic_data<T>::left_padding_shifts[] = {31, 31, 0, 1, 0};
+template <typename T>
+const char basic_data<T>::right_padding_shifts[] = {0, 31, 0, 1, 0};
 
 template <typename T> struct bits {
   static FMT_CONSTEXPR_DECL const int value =
@@ -356,6 +1096,14 @@
  private:
   using significand_type = uint64_t;
 
+  template <typename Float>
+  using is_supported_float = bool_constant<sizeof(Float) == sizeof(uint64_t) ||
+                                           sizeof(Float) == sizeof(uint32_t)>;
+
+ public:
+  significand_type f;
+  int e;
+
   // All sizes are in bits.
   // Subtract 1 to account for an implicit most significant bit in the
   // normalized form.
@@ -363,11 +1111,6 @@
       std::numeric_limits<double>::digits - 1;
   static FMT_CONSTEXPR_DECL const uint64_t implicit_bit =
       1ULL << double_significand_size;
-
- public:
-  significand_type f;
-  int e;
-
   static FMT_CONSTEXPR_DECL const int significand_size =
       bits<significand_type>::value;
 
@@ -378,81 +1121,57 @@
   // errors on platforms where double is not IEEE754.
   template <typename Double> explicit fp(Double d) { assign(d); }
 
-  // Normalizes the value converted from double and multiplied by (1 << SHIFT).
-  template <int SHIFT> friend fp normalize(fp value) {
-    // Handle subnormals.
-    const auto shifted_implicit_bit = fp::implicit_bit << SHIFT;
-    while ((value.f & shifted_implicit_bit) == 0) {
-      value.f <<= 1;
-      --value.e;
-    }
-    // Subtract 1 to account for hidden bit.
-    const auto offset =
-        fp::significand_size - fp::double_significand_size - SHIFT - 1;
-    value.f <<= offset;
-    value.e -= offset;
-    return value;
-  }
-
   // Assigns d to this and return true iff predecessor is closer than successor.
-  template <typename Double, FMT_ENABLE_IF(sizeof(Double) == sizeof(uint64_t))>
-  bool assign(Double d) {
-    // Assume double is in the format [sign][exponent][significand].
-    using limits = std::numeric_limits<Double>;
+  template <typename Float, FMT_ENABLE_IF(is_supported_float<Float>::value)>
+  bool assign(Float d) {
+    // Assume float is in the format [sign][exponent][significand].
+    using limits = std::numeric_limits<Float>;
+    const int float_significand_size = limits::digits - 1;
     const int exponent_size =
-        bits<Double>::value - double_significand_size - 1;  // -1 for sign
-    const uint64_t significand_mask = implicit_bit - 1;
+        bits<Float>::value - float_significand_size - 1;  // -1 for sign
+    const uint64_t float_implicit_bit = 1ULL << float_significand_size;
+    const uint64_t significand_mask = float_implicit_bit - 1;
     const uint64_t exponent_mask = (~0ULL >> 1) & ~significand_mask;
     const int exponent_bias = (1 << exponent_size) - limits::max_exponent - 1;
-    auto u = bit_cast<uint64_t>(d);
+    constexpr bool is_double = sizeof(Float) == sizeof(uint64_t);
+    auto u = bit_cast<conditional_t<is_double, uint64_t, uint32_t>>(d);
     f = u & significand_mask;
-    auto biased_e = (u & exponent_mask) >> double_significand_size;
+    int biased_e =
+        static_cast<int>((u & exponent_mask) >> float_significand_size);
     // Predecessor is closer if d is a normalized power of 2 (f == 0) other than
     // the smallest normalized number (biased_e > 1).
     bool is_predecessor_closer = f == 0 && biased_e > 1;
     if (biased_e != 0)
-      f += implicit_bit;
+      f += float_implicit_bit;
     else
       biased_e = 1;  // Subnormals use biased exponent 1 (min exponent).
-    e = static_cast<int>(biased_e - exponent_bias - double_significand_size);
+    e = biased_e - exponent_bias - float_significand_size;
     return is_predecessor_closer;
   }
 
-  template <typename Double, FMT_ENABLE_IF(sizeof(Double) != sizeof(uint64_t))>
-  bool assign(Double) {
+  template <typename Float, FMT_ENABLE_IF(!is_supported_float<Float>::value)>
+  bool assign(Float) {
     *this = fp();
     return false;
   }
-
-  // Assigns d to this together with computing lower and upper boundaries,
-  // where a boundary is a value half way between the number and its predecessor
-  // (lower) or successor (upper). The upper boundary is normalized and lower
-  // has the same exponent but may be not normalized.
-  template <typename Double> boundaries assign_with_boundaries(Double d) {
-    bool is_lower_closer = assign(d);
-    fp lower =
-        is_lower_closer ? fp((f << 2) - 1, e - 2) : fp((f << 1) - 1, e - 1);
-    // 1 in normalize accounts for the exponent shift above.
-    fp upper = normalize<1>(fp((f << 1) + 1, e - 1));
-    lower.f <<= lower.e - upper.e;
-    return boundaries{lower.f, upper.f};
-  }
-
-  template <typename Double> boundaries assign_float_with_boundaries(Double d) {
-    assign(d);
-    constexpr int min_normal_e = std::numeric_limits<float>::min_exponent -
-                                 std::numeric_limits<double>::digits;
-    significand_type half_ulp = 1 << (std::numeric_limits<double>::digits -
-                                      std::numeric_limits<float>::digits - 1);
-    if (min_normal_e > e) half_ulp <<= min_normal_e - e;
-    fp upper = normalize<0>(fp(f + half_ulp, e));
-    fp lower = fp(
-        f - (half_ulp >> ((f == implicit_bit && e > min_normal_e) ? 1 : 0)), e);
-    lower.f <<= lower.e - upper.e;
-    return boundaries{lower.f, upper.f};
-  }
 };
 
+// Normalizes the value converted from double and multiplied by (1 << SHIFT).
+template <int SHIFT> fp normalize(fp value) {
+  // Handle subnormals.
+  const auto shifted_implicit_bit = fp::implicit_bit << SHIFT;
+  while ((value.f & shifted_implicit_bit) == 0) {
+    value.f <<= 1;
+    --value.e;
+  }
+  // Subtract 1 to account for hidden bit.
+  const auto offset =
+      fp::significand_size - fp::double_significand_size - SHIFT - 1;
+  value.f <<= offset;
+  value.e -= offset;
+  return value;
+}
+
 inline bool operator==(fp x, fp y) { return x.f == y.f && x.e == y.e; }
 
 // Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
@@ -477,14 +1196,13 @@
 
 // Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
 // (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
-FMT_FUNC fp get_cached_power(int min_exponent, int& pow10_exponent) {
-  const uint64_t one_over_log2_10 = 0x4d104d42;  // round(pow(2, 32) / log2(10))
+inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
+  const int shift = 32;
+  const auto significand = static_cast<int64_t>(data::log10_2_significand);
   int index = static_cast<int>(
-      static_cast<int64_t>(
-          (min_exponent + fp::significand_size - 1) * one_over_log2_10 +
-          ((uint64_t(1) << 32) - 1)  // ceil
-          ) >>
-      32  // arithmetic shift
+      ((min_exponent + fp::significand_size - 1) * (significand >> shift) +
+       ((int64_t(1) << shift) - 1))  // ceil
+      >> 32                          // arithmetic shift
   );
   // Decimal exponent of the first (smallest) cached power of 10.
   const int first_dec_exp = -348;
@@ -492,7 +1210,8 @@
   const int dec_exp_step = 8;
   index = (index - first_dec_exp - 1) / dec_exp_step + 1;
   pow10_exponent = first_dec_exp + index * dec_exp_step;
-  return {data::pow10_significands[index], data::pow10_exponents[index]};
+  return {data::grisu_pow10_significands[index],
+          data::grisu_pow10_exponents[index]};
 }
 
 // A simple accumulator to hold the sums of terms in bigint::square if uint128_t
@@ -526,20 +1245,23 @@
   basic_memory_buffer<bigit, bigits_capacity> bigits_;
   int exp_;
 
+  bigit operator[](int index) const { return bigits_[to_unsigned(index)]; }
+  bigit& operator[](int index) { return bigits_[to_unsigned(index)]; }
+
   static FMT_CONSTEXPR_DECL const int bigit_bits = bits<bigit>::value;
 
   friend struct formatter<bigint>;
 
   void subtract_bigits(int index, bigit other, bigit& borrow) {
-    auto result = static_cast<double_bigit>(bigits_[index]) - other - borrow;
-    bigits_[index] = static_cast<bigit>(result);
+    auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
+    (*this)[index] = static_cast<bigit>(result);
     borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
   }
 
   void remove_leading_zeros() {
     int num_bigits = static_cast<int>(bigits_.size()) - 1;
-    while (num_bigits > 0 && bigits_[num_bigits] == 0) --num_bigits;
-    bigits_.resize(num_bigits + 1);
+    while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
+    bigits_.resize(to_unsigned(num_bigits + 1));
   }
 
   // Computes *this -= other assuming aligned bigints and *this >= other.
@@ -548,10 +1270,8 @@
     FMT_ASSERT(compare(*this, other) >= 0, "");
     bigit borrow = 0;
     int i = other.exp_ - exp_;
-    for (int j = 0, n = static_cast<int>(other.bigits_.size()); j != n;
-         ++i, ++j) {
+    for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j)
       subtract_bigits(i, other.bigits_[j], borrow);
-    }
     while (borrow > 0) subtract_bigits(i, 0, borrow);
     remove_leading_zeros();
   }
@@ -593,14 +1313,15 @@
   void operator=(const bigint&) = delete;
 
   void assign(const bigint& other) {
-    bigits_.resize(other.bigits_.size());
+    auto size = other.bigits_.size();
+    bigits_.resize(size);
     auto data = other.bigits_.data();
-    std::copy(data, data + other.bigits_.size(), bigits_.data());
+    std::copy(data, data + size, make_checked(bigits_.data(), size));
     exp_ = other.exp_;
   }
 
   void assign(uint64_t n) {
-    int num_bigits = 0;
+    size_t num_bigits = 0;
     do {
       bigits_[num_bigits++] = n & ~bigit(0);
       n >>= bigit_bits;
@@ -611,7 +1332,7 @@
 
   int num_bigits() const { return static_cast<int>(bigits_.size()) + exp_; }
 
-  bigint& operator<<=(int shift) {
+  FMT_NOINLINE bigint& operator<<=(int shift) {
     assert(shift >= 0);
     exp_ += shift / bigit_bits;
     shift %= bigit_bits;
@@ -641,7 +1362,7 @@
     int end = i - j;
     if (end < 0) end = 0;
     for (; i >= end; --i, --j) {
-      bigit lhs_bigit = lhs.bigits_[i], rhs_bigit = rhs.bigits_[j];
+      bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
       if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
     }
     if (i != j) return i > j ? 1 : -1;
@@ -656,7 +1377,7 @@
     if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
     if (max_lhs_bigits > num_rhs_bigits) return 1;
     auto get_bigit = [](const bigint& n, int i) -> bigit {
-      return i >= n.exp_ && i < n.num_bigits() ? n.bigits_[i - n.exp_] : 0;
+      return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
     };
     double_bigit borrow = 0;
     int min_exp = (std::min)((std::min)(lhs1.exp_, lhs2.exp_), rhs.exp_);
@@ -696,7 +1417,7 @@
     basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
     int num_bigits = static_cast<int>(bigits_.size());
     int num_result_bigits = 2 * num_bigits;
-    bigits_.resize(num_result_bigits);
+    bigits_.resize(to_unsigned(num_result_bigits));
     using accumulator_t = conditional_t<FMT_USE_INT128, uint128_t, accumulator>;
     auto sum = accumulator_t();
     for (int bigit_index = 0; bigit_index < num_bigits; ++bigit_index) {
@@ -706,7 +1427,7 @@
         // Most terms are multiplied twice which can be optimized in the future.
         sum += static_cast<double_bigit>(n[i]) * n[j];
       }
-      bigits_[bigit_index] = static_cast<bigit>(sum);
+      (*this)[bigit_index] = static_cast<bigit>(sum);
       sum >>= bits<bigit>::value;  // Compute the carry.
     }
     // Do the same for the top half.
@@ -714,7 +1435,7 @@
          ++bigit_index) {
       for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
         sum += static_cast<double_bigit>(n[i++]) * n[j--];
-      bigits_[bigit_index] = static_cast<bigit>(sum);
+      (*this)[bigit_index] = static_cast<bigit>(sum);
       sum >>= bits<bigit>::value;
     }
     --num_result_bigits;
@@ -722,22 +1443,26 @@
     exp_ *= 2;
   }
 
+  // If this bigint has a bigger exponent than other, adds trailing zero to make
+  // exponents equal. This simplifies some operations such as subtraction.
+  void align(const bigint& other) {
+    int exp_difference = exp_ - other.exp_;
+    if (exp_difference <= 0) return;
+    int num_bigits = static_cast<int>(bigits_.size());
+    bigits_.resize(to_unsigned(num_bigits + exp_difference));
+    for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
+      bigits_[j] = bigits_[i];
+    std::uninitialized_fill_n(bigits_.data(), exp_difference, 0);
+    exp_ -= exp_difference;
+  }
+
   // Divides this bignum by divisor, assigning the remainder to this and
   // returning the quotient.
   int divmod_assign(const bigint& divisor) {
     FMT_ASSERT(this != &divisor, "");
     if (compare(*this, divisor) < 0) return 0;
-    int num_bigits = static_cast<int>(bigits_.size());
-    FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1] != 0, "");
-    int exp_difference = exp_ - divisor.exp_;
-    if (exp_difference > 0) {
-      // Align bigints by adding trailing zeros to simplify subtraction.
-      bigits_.resize(num_bigits + exp_difference);
-      for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
-        bigits_[j] = bigits_[i];
-      std::uninitialized_fill_n(bigits_.data(), exp_difference, 0);
-      exp_ -= exp_difference;
-    }
+    FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
+    align(divisor);
     int quotient = 0;
     do {
       subtract_aligned(divisor);
@@ -747,7 +1472,7 @@
   }
 };
 
-enum round_direction { unknown, up, down };
+enum class round_direction { unknown, up, down };
 
 // Given the divisor (normally a power of 10), the remainder = v % divisor for
 // some number v and the error, returns whether v should be rounded up, down, or
@@ -760,13 +1485,13 @@
   FMT_ASSERT(error < divisor - error, "");  // error * 2 won't overflow.
   // Round down if (remainder + error) * 2 <= divisor.
   if (remainder <= divisor - remainder && error * 2 <= divisor - remainder * 2)
-    return down;
+    return round_direction::down;
   // Round up if (remainder - error) * 2 >= divisor.
   if (remainder >= error &&
       remainder - error >= divisor - (remainder - error)) {
-    return up;
+    return round_direction::up;
   }
-  return unknown;
+  return round_direction::unknown;
 }
 
 namespace digits {
@@ -842,8 +1567,7 @@
       FMT_ASSERT(false, "invalid number of digits");
     }
     --exp;
-    uint64_t remainder =
-        (static_cast<uint64_t>(integral) << -one.e) + fractional;
+    auto remainder = (static_cast<uint64_t>(integral) << -one.e) + fractional;
     result = handler.on_digit(static_cast<char>('0' + digit),
                               data::powers_of_10_64[exp] << -one.e, remainder,
                               error, exp, true);
@@ -853,8 +1577,7 @@
   for (;;) {
     fractional *= 10;
     error *= 10;
-    char digit =
-        static_cast<char>('0' + static_cast<char>(fractional >> -one.e));
+    char digit = static_cast<char>('0' + (fractional >> -one.e));
     fractional &= one.f - 1;
     --exp;
     result = handler.on_digit(digit, one.f, fractional, error, exp, false);
@@ -882,8 +1605,8 @@
     if (precision > 0) return digits::more;
     if (precision < 0) return digits::done;
     auto dir = get_round_direction(divisor, remainder, error);
-    if (dir == unknown) return digits::error;
-    buf[size++] = dir == up ? '1' : '0';
+    if (dir == round_direction::unknown) return digits::error;
+    buf[size++] = dir == round_direction::up ? '1' : '0';
     return digits::done;
   }
 
@@ -891,6 +1614,7 @@
                           uint64_t error, int, bool integral) {
     FMT_ASSERT(remainder < divisor, "");
     buf[size++] = digit;
+    if (!integral && error >= remainder) return digits::error;
     if (size < precision) return digits::more;
     if (!integral) {
       // Check if error * 2 < divisor with overflow prevention.
@@ -901,7 +1625,8 @@
       FMT_ASSERT(error == 1 && divisor > 2, "");
     }
     auto dir = get_round_direction(divisor, remainder, error);
-    if (dir != up) return dir == down ? digits::done : digits::error;
+    if (dir != round_direction::up)
+      return dir == round_direction::down ? digits::done : digits::error;
     ++buf[size - 1];
     for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
       buf[i] = '0';
@@ -909,59 +1634,684 @@
     }
     if (buf[0] > '9') {
       buf[0] = '1';
-      buf[size++] = '0';
+      if (fixed)
+        buf[size++] = '0';
+      else
+        ++exp10;
     }
     return digits::done;
   }
 };
 
-// The shortest representation digit handler.
-struct grisu_shortest_handler {
-  char* buf;
-  int size;
-  // Distance between scaled value and upper bound (wp_W in Grisu3).
-  uint64_t diff;
+// Implementation of Dragonbox algorithm: https://github.com/jk-jeon/dragonbox.
+namespace dragonbox {
+// Computes 128-bit result of multiplication of two 64-bit unsigned integers.
+FMT_SAFEBUFFERS inline uint128_wrapper umul128(uint64_t x,
+                                               uint64_t y) FMT_NOEXCEPT {
+#if FMT_USE_INT128
+  return static_cast<uint128_t>(x) * static_cast<uint128_t>(y);
+#elif defined(_MSC_VER) && defined(_M_X64)
+  uint128_wrapper result;
+  result.low_ = _umul128(x, y, &result.high_);
+  return result;
+#else
+  const uint64_t mask = (uint64_t(1) << 32) - uint64_t(1);
 
-  digits::result on_start(uint64_t, uint64_t, uint64_t, int&) {
-    return digits::more;
+  uint64_t a = x >> 32;
+  uint64_t b = x & mask;
+  uint64_t c = y >> 32;
+  uint64_t d = y & mask;
+
+  uint64_t ac = a * c;
+  uint64_t bc = b * c;
+  uint64_t ad = a * d;
+  uint64_t bd = b * d;
+
+  uint64_t intermediate = (bd >> 32) + (ad & mask) + (bc & mask);
+
+  return {ac + (intermediate >> 32) + (ad >> 32) + (bc >> 32),
+          (intermediate << 32) + (bd & mask)};
+#endif
+}
+
+// Computes upper 64 bits of multiplication of two 64-bit unsigned integers.
+FMT_SAFEBUFFERS inline uint64_t umul128_upper64(uint64_t x,
+                                                uint64_t y) FMT_NOEXCEPT {
+#if FMT_USE_INT128
+  auto p = static_cast<uint128_t>(x) * static_cast<uint128_t>(y);
+  return static_cast<uint64_t>(p >> 64);
+#elif defined(_MSC_VER) && defined(_M_X64)
+  return __umulh(x, y);
+#else
+  return umul128(x, y).high();
+#endif
+}
+
+// Computes upper 64 bits of multiplication of a 64-bit unsigned integer and a
+// 128-bit unsigned integer.
+FMT_SAFEBUFFERS inline uint64_t umul192_upper64(uint64_t x, uint128_wrapper y)
+    FMT_NOEXCEPT {
+  uint128_wrapper g0 = umul128(x, y.high());
+  g0 += umul128_upper64(x, y.low());
+  return g0.high();
+}
+
+// Computes upper 32 bits of multiplication of a 32-bit unsigned integer and a
+// 64-bit unsigned integer.
+inline uint32_t umul96_upper32(uint32_t x, uint64_t y) FMT_NOEXCEPT {
+  return static_cast<uint32_t>(umul128_upper64(x, y));
+}
+
+// Computes middle 64 bits of multiplication of a 64-bit unsigned integer and a
+// 128-bit unsigned integer.
+FMT_SAFEBUFFERS inline uint64_t umul192_middle64(uint64_t x, uint128_wrapper y)
+    FMT_NOEXCEPT {
+  uint64_t g01 = x * y.high();
+  uint64_t g10 = umul128_upper64(x, y.low());
+  return g01 + g10;
+}
+
+// Computes lower 64 bits of multiplication of a 32-bit unsigned integer and a
+// 64-bit unsigned integer.
+inline uint64_t umul96_lower64(uint32_t x, uint64_t y) FMT_NOEXCEPT {
+  return x * y;
+}
+
+// Computes floor(log10(pow(2, e))) for e in [-1700, 1700] using the method from
+// https://fmt.dev/papers/Grisu-Exact.pdf#page=5, section 3.4.
+inline int floor_log10_pow2(int e) FMT_NOEXCEPT {
+  FMT_ASSERT(e <= 1700 && e >= -1700, "too large exponent");
+  const int shift = 22;
+  return (e * static_cast<int>(data::log10_2_significand >> (64 - shift))) >>
+         shift;
+}
+
+// Various fast log computations.
+inline int floor_log2_pow10(int e) FMT_NOEXCEPT {
+  FMT_ASSERT(e <= 1233 && e >= -1233, "too large exponent");
+  const uint64_t log2_10_integer_part = 3;
+  const uint64_t log2_10_fractional_digits = 0x5269e12f346e2bf9;
+  const int shift_amount = 19;
+  return (e * static_cast<int>(
+                  (log2_10_integer_part << shift_amount) |
+                  (log2_10_fractional_digits >> (64 - shift_amount)))) >>
+         shift_amount;
+}
+inline int floor_log10_pow2_minus_log10_4_over_3(int e) FMT_NOEXCEPT {
+  FMT_ASSERT(e <= 1700 && e >= -1700, "too large exponent");
+  const uint64_t log10_4_over_3_fractional_digits = 0x1ffbfc2bbc780375;
+  const int shift_amount = 22;
+  return (e * static_cast<int>(data::log10_2_significand >>
+                               (64 - shift_amount)) -
+          static_cast<int>(log10_4_over_3_fractional_digits >>
+                           (64 - shift_amount))) >>
+         shift_amount;
+}
+
+// Returns true iff x is divisible by pow(2, exp).
+inline bool divisible_by_power_of_2(uint32_t x, int exp) FMT_NOEXCEPT {
+  FMT_ASSERT(exp >= 1, "");
+  FMT_ASSERT(x != 0, "");
+#ifdef FMT_BUILTIN_CTZ
+  return FMT_BUILTIN_CTZ(x) >= exp;
+#else
+  return exp < num_bits<uint32_t>() && x == ((x >> exp) << exp);
+#endif
+}
+inline bool divisible_by_power_of_2(uint64_t x, int exp) FMT_NOEXCEPT {
+  FMT_ASSERT(exp >= 1, "");
+  FMT_ASSERT(x != 0, "");
+#ifdef FMT_BUILTIN_CTZLL
+  return FMT_BUILTIN_CTZLL(x) >= exp;
+#else
+  return exp < num_bits<uint64_t>() && x == ((x >> exp) << exp);
+#endif
+}
+
+// Returns true iff x is divisible by pow(5, exp).
+inline bool divisible_by_power_of_5(uint32_t x, int exp) FMT_NOEXCEPT {
+  FMT_ASSERT(exp <= 10, "too large exponent");
+  return x * data::divtest_table_for_pow5_32[exp].mod_inv <=
+         data::divtest_table_for_pow5_32[exp].max_quotient;
+}
+inline bool divisible_by_power_of_5(uint64_t x, int exp) FMT_NOEXCEPT {
+  FMT_ASSERT(exp <= 23, "too large exponent");
+  return x * data::divtest_table_for_pow5_64[exp].mod_inv <=
+         data::divtest_table_for_pow5_64[exp].max_quotient;
+}
+
+// Replaces n by floor(n / pow(5, N)) returning true if and only if n is
+// divisible by pow(5, N).
+// Precondition: n <= 2 * pow(5, N + 1).
+template <int N>
+bool check_divisibility_and_divide_by_pow5(uint32_t& n) FMT_NOEXCEPT {
+  static constexpr struct {
+    uint32_t magic_number;
+    int bits_for_comparison;
+    uint32_t threshold;
+    int shift_amount;
+  } infos[] = {{0xcccd, 16, 0x3333, 18}, {0xa429, 8, 0x0a, 20}};
+  constexpr auto info = infos[N - 1];
+  n *= info.magic_number;
+  const uint32_t comparison_mask = (1u << info.bits_for_comparison) - 1;
+  bool result = (n & comparison_mask) <= info.threshold;
+  n >>= info.shift_amount;
+  return result;
+}
+
+// Computes floor(n / pow(10, N)) for small n and N.
+// Precondition: n <= pow(10, N + 1).
+template <int N> uint32_t small_division_by_pow10(uint32_t n) FMT_NOEXCEPT {
+  static constexpr struct {
+    uint32_t magic_number;
+    int shift_amount;
+    uint32_t divisor_times_10;
+  } infos[] = {{0xcccd, 19, 100}, {0xa3d8, 22, 1000}};
+  constexpr auto info = infos[N - 1];
+  FMT_ASSERT(n <= info.divisor_times_10, "n is too large");
+  return n * info.magic_number >> info.shift_amount;
+}
+
+// Computes floor(n / 10^(kappa + 1)) (float)
+inline uint32_t divide_by_10_to_kappa_plus_1(uint32_t n) FMT_NOEXCEPT {
+  return n / float_info<float>::big_divisor;
+}
+// Computes floor(n / 10^(kappa + 1)) (double)
+inline uint64_t divide_by_10_to_kappa_plus_1(uint64_t n) FMT_NOEXCEPT {
+  return umul128_upper64(n, 0x83126e978d4fdf3c) >> 9;
+}
+
+// Various subroutines using pow10 cache
+template <class T> struct cache_accessor;
+
+template <> struct cache_accessor<float> {
+  using carrier_uint = float_info<float>::carrier_uint;
+  using cache_entry_type = uint64_t;
+
+  static uint64_t get_cached_power(int k) FMT_NOEXCEPT {
+    FMT_ASSERT(k >= float_info<float>::min_k && k <= float_info<float>::max_k,
+               "k is out of range");
+    return data::dragonbox_pow10_significands_64[k - float_info<float>::min_k];
   }
 
-  // Decrement the generated number approaching value from above.
-  void round(uint64_t d, uint64_t divisor, uint64_t& remainder,
-             uint64_t error) {
-    while (
-        remainder < d && error - remainder >= divisor &&
-        (remainder + divisor < d || d - remainder >= remainder + divisor - d)) {
-      --buf[size - 1];
-      remainder += divisor;
-    }
+  static carrier_uint compute_mul(carrier_uint u,
+                                  const cache_entry_type& cache) FMT_NOEXCEPT {
+    return umul96_upper32(u, cache);
   }
 
-  // Implements Grisu's round_weed.
-  digits::result on_digit(char digit, uint64_t divisor, uint64_t remainder,
-                          uint64_t error, int exp, bool integral) {
-    buf[size++] = digit;
-    if (remainder >= error) return digits::more;
-    uint64_t unit = integral ? 1 : data::powers_of_10_64[-exp];
-    uint64_t up = (diff - 1) * unit;  // wp_Wup
-    round(up, divisor, remainder, error);
-    uint64_t down = (diff + 1) * unit;  // wp_Wdown
-    if (remainder < down && error - remainder >= divisor &&
-        (remainder + divisor < down ||
-         down - remainder > remainder + divisor - down)) {
-      return digits::error;
-    }
-    return 2 * unit <= remainder && remainder <= error - 4 * unit
-               ? digits::done
-               : digits::error;
+  static uint32_t compute_delta(const cache_entry_type& cache,
+                                int beta_minus_1) FMT_NOEXCEPT {
+    return static_cast<uint32_t>(cache >> (64 - 1 - beta_minus_1));
+  }
+
+  static bool compute_mul_parity(carrier_uint two_f,
+                                 const cache_entry_type& cache,
+                                 int beta_minus_1) FMT_NOEXCEPT {
+    FMT_ASSERT(beta_minus_1 >= 1, "");
+    FMT_ASSERT(beta_minus_1 < 64, "");
+
+    return ((umul96_lower64(two_f, cache) >> (64 - beta_minus_1)) & 1) != 0;
+  }
+
+  static carrier_uint compute_left_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta_minus_1) FMT_NOEXCEPT {
+    return static_cast<carrier_uint>(
+        (cache - (cache >> (float_info<float>::significand_bits + 2))) >>
+        (64 - float_info<float>::significand_bits - 1 - beta_minus_1));
+  }
+
+  static carrier_uint compute_right_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta_minus_1) FMT_NOEXCEPT {
+    return static_cast<carrier_uint>(
+        (cache + (cache >> (float_info<float>::significand_bits + 1))) >>
+        (64 - float_info<float>::significand_bits - 1 - beta_minus_1));
+  }
+
+  static carrier_uint compute_round_up_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta_minus_1) FMT_NOEXCEPT {
+    return (static_cast<carrier_uint>(
+                cache >>
+                (64 - float_info<float>::significand_bits - 2 - beta_minus_1)) +
+            1) /
+           2;
   }
 };
 
+template <> struct cache_accessor<double> {
+  using carrier_uint = float_info<double>::carrier_uint;
+  using cache_entry_type = uint128_wrapper;
+
+  static uint128_wrapper get_cached_power(int k) FMT_NOEXCEPT {
+    FMT_ASSERT(k >= float_info<double>::min_k && k <= float_info<double>::max_k,
+               "k is out of range");
+
+#if FMT_USE_FULL_CACHE_DRAGONBOX
+    return data::dragonbox_pow10_significands_128[k -
+                                                  float_info<double>::min_k];
+#else
+    static const int compression_ratio = 27;
+
+    // Compute base index.
+    int cache_index = (k - float_info<double>::min_k) / compression_ratio;
+    int kb = cache_index * compression_ratio + float_info<double>::min_k;
+    int offset = k - kb;
+
+    // Get base cache.
+    uint128_wrapper base_cache =
+        data::dragonbox_pow10_significands_128[cache_index];
+    if (offset == 0) return base_cache;
+
+    // Compute the required amount of bit-shift.
+    int alpha = floor_log2_pow10(kb + offset) - floor_log2_pow10(kb) - offset;
+    FMT_ASSERT(alpha > 0 && alpha < 64, "shifting error detected");
+
+    // Try to recover the real cache.
+    uint64_t pow5 = data::powers_of_5_64[offset];
+    uint128_wrapper recovered_cache = umul128(base_cache.high(), pow5);
+    uint128_wrapper middle_low =
+        umul128(base_cache.low() - (kb < 0 ? 1u : 0u), pow5);
+
+    recovered_cache += middle_low.high();
+
+    uint64_t high_to_middle = recovered_cache.high() << (64 - alpha);
+    uint64_t middle_to_low = recovered_cache.low() << (64 - alpha);
+
+    recovered_cache =
+        uint128_wrapper{(recovered_cache.low() >> alpha) | high_to_middle,
+                        ((middle_low.low() >> alpha) | middle_to_low)};
+
+    if (kb < 0) recovered_cache += 1;
+
+    // Get error.
+    int error_idx = (k - float_info<double>::min_k) / 16;
+    uint32_t error = (data::dragonbox_pow10_recovery_errors[error_idx] >>
+                      ((k - float_info<double>::min_k) % 16) * 2) &
+                     0x3;
+
+    // Add the error back.
+    FMT_ASSERT(recovered_cache.low() + error >= recovered_cache.low(), "");
+    return {recovered_cache.high(), recovered_cache.low() + error};
+#endif
+  }
+
+  static carrier_uint compute_mul(carrier_uint u,
+                                  const cache_entry_type& cache) FMT_NOEXCEPT {
+    return umul192_upper64(u, cache);
+  }
+
+  static uint32_t compute_delta(cache_entry_type const& cache,
+                                int beta_minus_1) FMT_NOEXCEPT {
+    return static_cast<uint32_t>(cache.high() >> (64 - 1 - beta_minus_1));
+  }
+
+  static bool compute_mul_parity(carrier_uint two_f,
+                                 const cache_entry_type& cache,
+                                 int beta_minus_1) FMT_NOEXCEPT {
+    FMT_ASSERT(beta_minus_1 >= 1, "");
+    FMT_ASSERT(beta_minus_1 < 64, "");
+
+    return ((umul192_middle64(two_f, cache) >> (64 - beta_minus_1)) & 1) != 0;
+  }
+
+  static carrier_uint compute_left_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta_minus_1) FMT_NOEXCEPT {
+    return (cache.high() -
+            (cache.high() >> (float_info<double>::significand_bits + 2))) >>
+           (64 - float_info<double>::significand_bits - 1 - beta_minus_1);
+  }
+
+  static carrier_uint compute_right_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta_minus_1) FMT_NOEXCEPT {
+    return (cache.high() +
+            (cache.high() >> (float_info<double>::significand_bits + 1))) >>
+           (64 - float_info<double>::significand_bits - 1 - beta_minus_1);
+  }
+
+  static carrier_uint compute_round_up_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta_minus_1) FMT_NOEXCEPT {
+    return ((cache.high() >>
+             (64 - float_info<double>::significand_bits - 2 - beta_minus_1)) +
+            1) /
+           2;
+  }
+};
+
+// Various integer checks
+template <class T>
+bool is_left_endpoint_integer_shorter_interval(int exponent) FMT_NOEXCEPT {
+  return exponent >=
+             float_info<
+                 T>::case_shorter_interval_left_endpoint_lower_threshold &&
+         exponent <=
+             float_info<T>::case_shorter_interval_left_endpoint_upper_threshold;
+}
+template <class T>
+bool is_endpoint_integer(typename float_info<T>::carrier_uint two_f,
+                         int exponent, int minus_k) FMT_NOEXCEPT {
+  if (exponent < float_info<T>::case_fc_pm_half_lower_threshold) return false;
+  // For k >= 0.
+  if (exponent <= float_info<T>::case_fc_pm_half_upper_threshold) return true;
+  // For k < 0.
+  if (exponent > float_info<T>::divisibility_check_by_5_threshold) return false;
+  return divisible_by_power_of_5(two_f, minus_k);
+}
+
+template <class T>
+bool is_center_integer(typename float_info<T>::carrier_uint two_f, int exponent,
+                       int minus_k) FMT_NOEXCEPT {
+  // Exponent for 5 is negative.
+  if (exponent > float_info<T>::divisibility_check_by_5_threshold) return false;
+  if (exponent > float_info<T>::case_fc_upper_threshold)
+    return divisible_by_power_of_5(two_f, minus_k);
+  // Both exponents are nonnegative.
+  if (exponent >= float_info<T>::case_fc_lower_threshold) return true;
+  // Exponent for 2 is negative.
+  return divisible_by_power_of_2(two_f, minus_k - exponent + 1);
+}
+
+// Remove trailing zeros from n and return the number of zeros removed (float)
+FMT_ALWAYS_INLINE int remove_trailing_zeros(uint32_t& n) FMT_NOEXCEPT {
+#ifdef FMT_BUILTIN_CTZ
+  int t = FMT_BUILTIN_CTZ(n);
+#else
+  int t = ctz(n);
+#endif
+  if (t > float_info<float>::max_trailing_zeros)
+    t = float_info<float>::max_trailing_zeros;
+
+  const uint32_t mod_inv1 = 0xcccccccd;
+  const uint32_t max_quotient1 = 0x33333333;
+  const uint32_t mod_inv2 = 0xc28f5c29;
+  const uint32_t max_quotient2 = 0x0a3d70a3;
+
+  int s = 0;
+  for (; s < t - 1; s += 2) {
+    if (n * mod_inv2 > max_quotient2) break;
+    n *= mod_inv2;
+  }
+  if (s < t && n * mod_inv1 <= max_quotient1) {
+    n *= mod_inv1;
+    ++s;
+  }
+  n >>= s;
+  return s;
+}
+
+// Removes trailing zeros and returns the number of zeros removed (double)
+FMT_ALWAYS_INLINE int remove_trailing_zeros(uint64_t& n) FMT_NOEXCEPT {
+#ifdef FMT_BUILTIN_CTZLL
+  int t = FMT_BUILTIN_CTZLL(n);
+#else
+  int t = ctzll(n);
+#endif
+  if (t > float_info<double>::max_trailing_zeros)
+    t = float_info<double>::max_trailing_zeros;
+  // Divide by 10^8 and reduce to 32-bits
+  // Since ret_value.significand <= (2^64 - 1) / 1000 < 10^17,
+  // both of the quotient and the r should fit in 32-bits
+
+  const uint32_t mod_inv1 = 0xcccccccd;
+  const uint32_t max_quotient1 = 0x33333333;
+  const uint64_t mod_inv8 = 0xc767074b22e90e21;
+  const uint64_t max_quotient8 = 0x00002af31dc46118;
+
+  // If the number is divisible by 1'0000'0000, work with the quotient
+  if (t >= 8) {
+    auto quotient_candidate = n * mod_inv8;
+
+    if (quotient_candidate <= max_quotient8) {
+      auto quotient = static_cast<uint32_t>(quotient_candidate >> 8);
+
+      int s = 8;
+      for (; s < t; ++s) {
+        if (quotient * mod_inv1 > max_quotient1) break;
+        quotient *= mod_inv1;
+      }
+      quotient >>= (s - 8);
+      n = quotient;
+      return s;
+    }
+  }
+
+  // Otherwise, work with the remainder
+  auto quotient = static_cast<uint32_t>(n / 100000000);
+  auto remainder = static_cast<uint32_t>(n - 100000000 * quotient);
+
+  if (t == 0 || remainder * mod_inv1 > max_quotient1) {
+    return 0;
+  }
+  remainder *= mod_inv1;
+
+  if (t == 1 || remainder * mod_inv1 > max_quotient1) {
+    n = (remainder >> 1) + quotient * 10000000ull;
+    return 1;
+  }
+  remainder *= mod_inv1;
+
+  if (t == 2 || remainder * mod_inv1 > max_quotient1) {
+    n = (remainder >> 2) + quotient * 1000000ull;
+    return 2;
+  }
+  remainder *= mod_inv1;
+
+  if (t == 3 || remainder * mod_inv1 > max_quotient1) {
+    n = (remainder >> 3) + quotient * 100000ull;
+    return 3;
+  }
+  remainder *= mod_inv1;
+
+  if (t == 4 || remainder * mod_inv1 > max_quotient1) {
+    n = (remainder >> 4) + quotient * 10000ull;
+    return 4;
+  }
+  remainder *= mod_inv1;
+
+  if (t == 5 || remainder * mod_inv1 > max_quotient1) {
+    n = (remainder >> 5) + quotient * 1000ull;
+    return 5;
+  }
+  remainder *= mod_inv1;
+
+  if (t == 6 || remainder * mod_inv1 > max_quotient1) {
+    n = (remainder >> 6) + quotient * 100ull;
+    return 6;
+  }
+  remainder *= mod_inv1;
+
+  n = (remainder >> 7) + quotient * 10ull;
+  return 7;
+}
+
+// The main algorithm for shorter interval case
+template <class T>
+FMT_ALWAYS_INLINE FMT_SAFEBUFFERS decimal_fp<T> shorter_interval_case(
+    int exponent) FMT_NOEXCEPT {
+  decimal_fp<T> ret_value;
+  // Compute k and beta
+  const int minus_k = floor_log10_pow2_minus_log10_4_over_3(exponent);
+  const int beta_minus_1 = exponent + floor_log2_pow10(-minus_k);
+
+  // Compute xi and zi
+  using cache_entry_type = typename cache_accessor<T>::cache_entry_type;
+  const cache_entry_type cache = cache_accessor<T>::get_cached_power(-minus_k);
+
+  auto xi = cache_accessor<T>::compute_left_endpoint_for_shorter_interval_case(
+      cache, beta_minus_1);
+  auto zi = cache_accessor<T>::compute_right_endpoint_for_shorter_interval_case(
+      cache, beta_minus_1);
+
+  // If the left endpoint is not an integer, increase it
+  if (!is_left_endpoint_integer_shorter_interval<T>(exponent)) ++xi;
+
+  // Try bigger divisor
+  ret_value.significand = zi / 10;
+
+  // If succeed, remove trailing zeros if necessary and return
+  if (ret_value.significand * 10 >= xi) {
+    ret_value.exponent = minus_k + 1;
+    ret_value.exponent += remove_trailing_zeros(ret_value.significand);
+    return ret_value;
+  }
+
+  // Otherwise, compute the round-up of y
+  ret_value.significand =
+      cache_accessor<T>::compute_round_up_for_shorter_interval_case(
+          cache, beta_minus_1);
+  ret_value.exponent = minus_k;
+
+  // When tie occurs, choose one of them according to the rule
+  if (exponent >= float_info<T>::shorter_interval_tie_lower_threshold &&
+      exponent <= float_info<T>::shorter_interval_tie_upper_threshold) {
+    ret_value.significand = ret_value.significand % 2 == 0
+                                ? ret_value.significand
+                                : ret_value.significand - 1;
+  } else if (ret_value.significand < xi) {
+    ++ret_value.significand;
+  }
+  return ret_value;
+}
+
+template <typename T>
+FMT_SAFEBUFFERS decimal_fp<T> to_decimal(T x) FMT_NOEXCEPT {
+  // Step 1: integer promotion & Schubfach multiplier calculation.
+
+  using carrier_uint = typename float_info<T>::carrier_uint;
+  using cache_entry_type = typename cache_accessor<T>::cache_entry_type;
+  auto br = bit_cast<carrier_uint>(x);
+
+  // Extract significand bits and exponent bits.
+  const carrier_uint significand_mask =
+      (static_cast<carrier_uint>(1) << float_info<T>::significand_bits) - 1;
+  carrier_uint significand = (br & significand_mask);
+  int exponent = static_cast<int>((br & exponent_mask<T>()) >>
+                                  float_info<T>::significand_bits);
+
+  if (exponent != 0) {  // Check if normal.
+    exponent += float_info<T>::exponent_bias - float_info<T>::significand_bits;
+
+    // Shorter interval case; proceed like Schubfach.
+    if (significand == 0) return shorter_interval_case<T>(exponent);
+
+    significand |=
+        (static_cast<carrier_uint>(1) << float_info<T>::significand_bits);
+  } else {
+    // Subnormal case; the interval is always regular.
+    if (significand == 0) return {0, 0};
+    exponent = float_info<T>::min_exponent - float_info<T>::significand_bits;
+  }
+
+  const bool include_left_endpoint = (significand % 2 == 0);
+  const bool include_right_endpoint = include_left_endpoint;
+
+  // Compute k and beta.
+  const int minus_k = floor_log10_pow2(exponent) - float_info<T>::kappa;
+  const cache_entry_type cache = cache_accessor<T>::get_cached_power(-minus_k);
+  const int beta_minus_1 = exponent + floor_log2_pow10(-minus_k);
+
+  // Compute zi and deltai
+  // 10^kappa <= deltai < 10^(kappa + 1)
+  const uint32_t deltai = cache_accessor<T>::compute_delta(cache, beta_minus_1);
+  const carrier_uint two_fc = significand << 1;
+  const carrier_uint two_fr = two_fc | 1;
+  const carrier_uint zi =
+      cache_accessor<T>::compute_mul(two_fr << beta_minus_1, cache);
+
+  // Step 2: Try larger divisor; remove trailing zeros if necessary
+
+  // Using an upper bound on zi, we might be able to optimize the division
+  // better than the compiler; we are computing zi / big_divisor here
+  decimal_fp<T> ret_value;
+  ret_value.significand = divide_by_10_to_kappa_plus_1(zi);
+  uint32_t r = static_cast<uint32_t>(zi - float_info<T>::big_divisor *
+                                              ret_value.significand);
+
+  if (r > deltai) {
+    goto small_divisor_case_label;
+  } else if (r < deltai) {
+    // Exclude the right endpoint if necessary
+    if (r == 0 && !include_right_endpoint &&
+        is_endpoint_integer<T>(two_fr, exponent, minus_k)) {
+      --ret_value.significand;
+      r = float_info<T>::big_divisor;
+      goto small_divisor_case_label;
+    }
+  } else {
+    // r == deltai; compare fractional parts
+    // Check conditions in the order different from the paper
+    // to take advantage of short-circuiting
+    const carrier_uint two_fl = two_fc - 1;
+    if ((!include_left_endpoint ||
+         !is_endpoint_integer<T>(two_fl, exponent, minus_k)) &&
+        !cache_accessor<T>::compute_mul_parity(two_fl, cache, beta_minus_1)) {
+      goto small_divisor_case_label;
+    }
+  }
+  ret_value.exponent = minus_k + float_info<T>::kappa + 1;
+
+  // We may need to remove trailing zeros
+  ret_value.exponent += remove_trailing_zeros(ret_value.significand);
+  return ret_value;
+
+  // Step 3: Find the significand with the smaller divisor
+
+small_divisor_case_label:
+  ret_value.significand *= 10;
+  ret_value.exponent = minus_k + float_info<T>::kappa;
+
+  const uint32_t mask = (1u << float_info<T>::kappa) - 1;
+  auto dist = r - (deltai / 2) + (float_info<T>::small_divisor / 2);
+
+  // Is dist divisible by 2^kappa?
+  if ((dist & mask) == 0) {
+    const bool approx_y_parity =
+        ((dist ^ (float_info<T>::small_divisor / 2)) & 1) != 0;
+    dist >>= float_info<T>::kappa;
+
+    // Is dist divisible by 5^kappa?
+    if (check_divisibility_and_divide_by_pow5<float_info<T>::kappa>(dist)) {
+      ret_value.significand += dist;
+
+      // Check z^(f) >= epsilon^(f)
+      // We have either yi == zi - epsiloni or yi == (zi - epsiloni) - 1,
+      // where yi == zi - epsiloni if and only if z^(f) >= epsilon^(f)
+      // Since there are only 2 possibilities, we only need to care about the
+      // parity. Also, zi and r should have the same parity since the divisor
+      // is an even number
+      if (cache_accessor<T>::compute_mul_parity(two_fc, cache, beta_minus_1) !=
+          approx_y_parity) {
+        --ret_value.significand;
+      } else {
+        // If z^(f) >= epsilon^(f), we might have a tie
+        // when z^(f) == epsilon^(f), or equivalently, when y is an integer
+        if (is_center_integer<T>(two_fc, exponent, minus_k)) {
+          ret_value.significand = ret_value.significand % 2 == 0
+                                      ? ret_value.significand
+                                      : ret_value.significand - 1;
+        }
+      }
+    }
+    // Is dist not divisible by 5^kappa?
+    else {
+      ret_value.significand += dist;
+    }
+  }
+  // Is dist not divisible by 2^kappa?
+  else {
+    // Since we know dist is small, we might be able to optimize the division
+    // better than the compiler; we are computing dist / small_divisor here
+    ret_value.significand +=
+        small_division_by_pow10<float_info<T>::kappa>(dist);
+  }
+  return ret_value;
+}
+}  // namespace dragonbox
+
 // Formats value using a variation of the Fixed-Precision Positive
 // Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
 // https://fmt.dev/p372-steele.pdf.
 template <typename Double>
-void fallback_format(Double d, buffer<char>& buf, int& exp10) {
+void fallback_format(Double d, int num_digits, bool binary32, buffer<char>& buf,
+                     int& exp10) {
   bigint numerator;    // 2 * R in (FPP)^2.
   bigint denominator;  // 2 * S in (FPP)^2.
   // lower and upper are differences between value and corresponding boundaries.
@@ -972,8 +2322,9 @@
   // Shift numerator and denominator by an extra bit or two (if lower boundary
   // is closer) to make lower and upper integers. This eliminates multiplication
   // by 2 during later computations.
-  // TODO: handle float
-  int shift = value.assign(d) ? 2 : 1;
+  const bool is_predecessor_closer =
+      binary32 ? value.assign(static_cast<float>(d)) : value.assign(d);
+  int shift = is_predecessor_closer ? 2 : 1;
   uint64_t significand = value.f << shift;
   if (value.e >= 0) {
     numerator.assign(significand);
@@ -986,7 +2337,7 @@
       upper = &upper_store;
     }
     denominator.assign_pow10(exp10);
-    denominator <<= 1;
+    denominator <<= shift;
   } else if (exp10 < 0) {
     numerator.assign_pow10(-exp10);
     lower.assign(numerator);
@@ -1008,42 +2359,76 @@
       upper = &upper_store;
     }
   }
-  if (!upper) upper = &lower;
   // Invariant: value == (numerator / denominator) * pow(10, exp10).
-  bool even = (value.f & 1) == 0;
-  int num_digits = 0;
-  char* data = buf.data();
-  for (;;) {
-    int digit = numerator.divmod_assign(denominator);
-    bool low = compare(numerator, lower) - even < 0;  // numerator <[=] lower.
-    // numerator + upper >[=] pow10:
-    bool high = add_compare(numerator, *upper, denominator) + even > 0;
-    data[num_digits++] = static_cast<char>('0' + digit);
-    if (low || high) {
-      if (!low) {
-        ++data[num_digits - 1];
-      } else if (high) {
-        int result = add_compare(numerator, numerator, denominator);
-        // Round half to even.
-        if (result > 0 || (result == 0 && (digit % 2) != 0))
+  if (num_digits < 0) {
+    // Generate the shortest representation.
+    if (!upper) upper = &lower;
+    bool even = (value.f & 1) == 0;
+    num_digits = 0;
+    char* data = buf.data();
+    for (;;) {
+      int digit = numerator.divmod_assign(denominator);
+      bool low = compare(numerator, lower) - even < 0;  // numerator <[=] lower.
+      // numerator + upper >[=] pow10:
+      bool high = add_compare(numerator, *upper, denominator) + even > 0;
+      data[num_digits++] = static_cast<char>('0' + digit);
+      if (low || high) {
+        if (!low) {
           ++data[num_digits - 1];
+        } else if (high) {
+          int result = add_compare(numerator, numerator, denominator);
+          // Round half to even.
+          if (result > 0 || (result == 0 && (digit % 2) != 0))
+            ++data[num_digits - 1];
+        }
+        buf.try_resize(to_unsigned(num_digits));
+        exp10 -= num_digits - 1;
+        return;
       }
-      buf.resize(num_digits);
-      exp10 -= num_digits - 1;
+      numerator *= 10;
+      lower *= 10;
+      if (upper != &lower) *upper *= 10;
+    }
+  }
+  // Generate the given number of digits.
+  exp10 -= num_digits - 1;
+  if (num_digits == 0) {
+    buf.try_resize(1);
+    denominator *= 10;
+    buf[0] = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
+    return;
+  }
+  buf.try_resize(to_unsigned(num_digits));
+  for (int i = 0; i < num_digits - 1; ++i) {
+    int digit = numerator.divmod_assign(denominator);
+    buf[i] = static_cast<char>('0' + digit);
+    numerator *= 10;
+  }
+  int digit = numerator.divmod_assign(denominator);
+  auto result = add_compare(numerator, numerator, denominator);
+  if (result > 0 || (result == 0 && (digit % 2) != 0)) {
+    if (digit == 9) {
+      const auto overflow = '0' + 10;
+      buf[num_digits - 1] = overflow;
+      // Propagate the carry.
+      for (int i = num_digits - 1; i > 0 && buf[i] == overflow; --i) {
+        buf[i] = '0';
+        ++buf[i - 1];
+      }
+      if (buf[0] == overflow) {
+        buf[0] = '1';
+        ++exp10;
+      }
       return;
     }
-    numerator *= 10;
-    lower *= 10;
-    if (upper != &lower) *upper *= 10;
+    ++digit;
   }
+  buf[num_digits - 1] = static_cast<char>('0' + digit);
 }
 
-// Formats value using the Grisu algorithm
-// (https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf)
-// if T is a IEEE754 binary32 or binary64 and snprintf otherwise.
 template <typename T>
 int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
-  static_assert(!std::is_same<T, float>(), "");
+  static_assert(!std::is_same<T, float>::value, "");
   FMT_ASSERT(value >= 0, "value is negative");
 
   const bool fixed = specs.format == float_format::fixed;
@@ -1052,73 +2437,64 @@
       buf.push_back('0');
       return 0;
     }
-    buf.resize(to_unsigned(precision));
+    buf.try_resize(to_unsigned(precision));
     std::uninitialized_fill_n(buf.data(), precision, '0');
     return -precision;
   }
 
   if (!specs.use_grisu) return snprintf_float(value, precision, specs, buf);
 
+  if (precision < 0) {
+    // Use Dragonbox for the shortest format.
+    if (specs.binary32) {
+      auto dec = dragonbox::to_decimal(static_cast<float>(value));
+      write<char>(buffer_appender<char>(buf), dec.significand);
+      return dec.exponent;
+    }
+    auto dec = dragonbox::to_decimal(static_cast<double>(value));
+    write<char>(buffer_appender<char>(buf), dec.significand);
+    return dec.exponent;
+  }
+
+  // Use Grisu + Dragon4 for the given precision:
+  // https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf.
   int exp = 0;
   const int min_exp = -60;  // alpha in Grisu.
   int cached_exp10 = 0;     // K in Grisu.
-  if (precision != -1) {
-    if (precision > 17) return snprintf_float(value, precision, specs, buf);
-    fp normalized = normalize(fp(value));
-    const auto cached_pow = get_cached_power(
-        min_exp - (normalized.e + fp::significand_size), cached_exp10);
-    normalized = normalized * cached_pow;
-    fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
-    if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error)
-      return snprintf_float(value, precision, specs, buf);
-    int num_digits = handler.size;
-    if (!fixed) {
-      // Remove trailing zeros.
-      while (num_digits > 0 && buf[num_digits - 1] == '0') {
-        --num_digits;
-        ++exp;
-      }
-    }
-    buf.resize(to_unsigned(num_digits));
+  fp normalized = normalize(fp(value));
+  const auto cached_pow = get_cached_power(
+      min_exp - (normalized.e + fp::significand_size), cached_exp10);
+  normalized = normalized * cached_pow;
+  // Limit precision to the maximum possible number of significant digits in an
+  // IEEE754 double because we don't need to generate zeros.
+  const int max_double_digits = 767;
+  if (precision > max_double_digits) precision = max_double_digits;
+  fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
+  if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error) {
+    exp += handler.size - cached_exp10 - 1;
+    fallback_format(value, handler.precision, specs.binary32, buf, exp);
   } else {
-    fp fp_value;
-    auto boundaries = specs.binary32
-                          ? fp_value.assign_float_with_boundaries(value)
-                          : fp_value.assign_with_boundaries(value);
-    fp_value = normalize(fp_value);
-    // Find a cached power of 10 such that multiplying value by it will bring
-    // the exponent in the range [min_exp, -32].
-    const fp cached_pow = get_cached_power(
-        min_exp - (fp_value.e + fp::significand_size), cached_exp10);
-    // Multiply value and boundaries by the cached power of 10.
-    fp_value = fp_value * cached_pow;
-    boundaries.lower = multiply(boundaries.lower, cached_pow.f);
-    boundaries.upper = multiply(boundaries.upper, cached_pow.f);
-    assert(min_exp <= fp_value.e && fp_value.e <= -32);
-    --boundaries.lower;  // \tilde{M}^- - 1 ulp -> M^-_{\downarrow}.
-    ++boundaries.upper;  // \tilde{M}^+ + 1 ulp -> M^+_{\uparrow}.
-    // Numbers outside of (lower, upper) definitely do not round to value.
-    grisu_shortest_handler handler{buf.data(), 0,
-                                   boundaries.upper - fp_value.f};
-    auto result =
-        grisu_gen_digits(fp(boundaries.upper, fp_value.e),
-                         boundaries.upper - boundaries.lower, exp, handler);
-    if (result == digits::error) {
-      exp += handler.size - cached_exp10 - 1;
-      fallback_format(value, buf, exp);
-      return exp;
-    }
-    buf.resize(to_unsigned(handler.size));
+    exp += handler.exp10;
+    buf.try_resize(to_unsigned(handler.size));
   }
-  return exp - cached_exp10;
-}
+  if (!fixed && !specs.showpoint) {
+    // Remove trailing zeros.
+    auto num_digits = buf.size();
+    while (num_digits > 0 && buf[num_digits - 1] == '0') {
+      --num_digits;
+      ++exp;
+    }
+    buf.try_resize(num_digits);
+  }
+  return exp;
+}  // namespace detail
 
 template <typename T>
 int snprintf_float(T value, int precision, float_specs specs,
                    buffer<char>& buf) {
   // Buffer capacity must be non-zero, otherwise MSVC's vsnprintf_s will fail.
   FMT_ASSERT(buf.capacity() > buf.size(), "empty buffer");
-  static_assert(!std::is_same<T, float>(), "");
+  static_assert(!std::is_same<T, float>::value, "");
 
   // Subtract 1 to account for the difference in precision since we use %e for
   // both general and exponent format.
@@ -1127,11 +2503,11 @@
     precision = (precision >= 0 ? precision : 6) - 1;
 
   // Build the format string.
-  enum { max_format_size = 7 };  // Ths longest format is "%#.*Le".
+  enum { max_format_size = 7 };  // The longest format is "%#.*Le".
   char format[max_format_size];
   char* format_ptr = format;
   *format_ptr++ = '%';
-  if (specs.trailing_zeros) *format_ptr++ = '#';
+  if (specs.showpoint && specs.format == float_format::hex) *format_ptr++ = '#';
   if (precision >= 0) {
     *format_ptr++ = '.';
     *format_ptr++ = '*';
@@ -1147,30 +2523,32 @@
   for (;;) {
     auto begin = buf.data() + offset;
     auto capacity = buf.capacity() - offset;
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#ifdef FMT_FUZZ
     if (precision > 100000)
       throw std::runtime_error(
           "fuzz mode - avoid large allocation inside snprintf");
 #endif
     // Suppress the warning about a nonliteral format string.
-    auto snprintf_ptr = FMT_SNPRINTF;
+    // Cannot use auto because of a bug in MinGW (#1532).
+    int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
     int result = precision >= 0
                      ? snprintf_ptr(begin, capacity, format, precision, value)
                      : snprintf_ptr(begin, capacity, format, value);
     if (result < 0) {
-      buf.reserve(buf.capacity() + 1);  // The buffer will grow exponentially.
+      // The buffer will grow exponentially.
+      buf.try_reserve(buf.capacity() + 1);
       continue;
     }
-    unsigned size = to_unsigned(result);
+    auto size = to_unsigned(result);
     // Size equal to capacity means that the last character was truncated.
     if (size >= capacity) {
-      buf.reserve(size + offset + 1);  // Add 1 for the terminating '\0'.
+      buf.try_reserve(size + offset + 1);  // Add 1 for the terminating '\0'.
       continue;
     }
     auto is_digit = [](char c) { return c >= '0' && c <= '9'; };
     if (specs.format == float_format::fixed) {
       if (precision == 0) {
-        buf.resize(size);
+        buf.try_resize(size);
         return 0;
       }
       // Find and remove the decimal point.
@@ -1179,12 +2557,12 @@
         --p;
       } while (is_digit(*p));
       int fraction_size = static_cast<int>(end - p - 1);
-      std::memmove(p, p + 1, fraction_size);
-      buf.resize(size - 1);
+      std::memmove(p, p + 1, to_unsigned(fraction_size));
+      buf.try_resize(size - 1);
       return -fraction_size;
     }
     if (specs.format == float_format::hex) {
-      buf.resize(size + offset);
+      buf.try_resize(size + offset);
       return 0;
     }
     // Find and parse the exponent.
@@ -1208,25 +2586,86 @@
       while (*fraction_end == '0') --fraction_end;
       // Move the fractional part left to get rid of the decimal point.
       fraction_size = static_cast<int>(fraction_end - begin - 1);
-      std::memmove(begin + 1, begin + 2, fraction_size);
+      std::memmove(begin + 1, begin + 2, to_unsigned(fraction_size));
     }
-    buf.resize(fraction_size + offset + 1);
+    buf.try_resize(to_unsigned(fraction_size) + offset + 1);
     return exp - fraction_size;
   }
 }
-}  // namespace internal
 
-template <> struct formatter<internal::bigint> {
+// A public domain branchless UTF-8 decoder by Christopher Wellons:
+// https://github.com/skeeto/branchless-utf8
+/* Decode the next character, c, from buf, reporting errors in e.
+ *
+ * Since this is a branchless decoder, four bytes will be read from the
+ * buffer regardless of the actual length of the next character. This
+ * means the buffer _must_ have at least three bytes of zero padding
+ * following the end of the data stream.
+ *
+ * Errors are reported in e, which will be non-zero if the parsed
+ * character was somehow invalid: invalid byte sequence, non-canonical
+ * encoding, or a surrogate half.
+ *
+ * The function returns a pointer to the next character. When an error
+ * occurs, this pointer will be a guess that depends on the particular
+ * error, but it will always advance at least one byte.
+ */
+inline const char* utf8_decode(const char* buf, uint32_t* c, int* e) {
+  static const int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
+  static const uint32_t mins[] = {4194304, 0, 128, 2048, 65536};
+  static const int shiftc[] = {0, 18, 12, 6, 0};
+  static const int shifte[] = {0, 6, 4, 2, 0};
+
+  int len = code_point_length(buf);
+  const char* next = buf + len;
+
+  // Assume a four-byte character and load four bytes. Unused bits are
+  // shifted out.
+  auto s = reinterpret_cast<const unsigned char*>(buf);
+  *c = uint32_t(s[0] & masks[len]) << 18;
+  *c |= uint32_t(s[1] & 0x3f) << 12;
+  *c |= uint32_t(s[2] & 0x3f) << 6;
+  *c |= uint32_t(s[3] & 0x3f) << 0;
+  *c >>= shiftc[len];
+
+  // Accumulate the various error conditions.
+  *e = (*c < mins[len]) << 6;       // non-canonical encoding
+  *e |= ((*c >> 11) == 0x1b) << 7;  // surrogate half?
+  *e |= (*c > 0x10FFFF) << 8;       // out of range?
+  *e |= (s[1] & 0xc0) >> 2;
+  *e |= (s[2] & 0xc0) >> 4;
+  *e |= (s[3]) >> 6;
+  *e ^= 0x2a;  // top two bits of each tail byte correct?
+  *e >>= shifte[len];
+
+  return next;
+}
+
+struct stringifier {
+  template <typename T> FMT_INLINE std::string operator()(T value) const {
+    return to_string(value);
+  }
+  std::string operator()(basic_format_arg<format_context>::handle h) const {
+    memory_buffer buf;
+    format_parse_context parse_ctx({});
+    format_context format_ctx(buffer_appender<char>(buf), {}, {});
+    h.format(parse_ctx, format_ctx);
+    return to_string(buf);
+  }
+};
+}  // namespace detail
+
+template <> struct formatter<detail::bigint> {
   format_parse_context::iterator parse(format_parse_context& ctx) {
     return ctx.begin();
   }
 
-  format_context::iterator format(const internal::bigint& n,
+  format_context::iterator format(const detail::bigint& n,
                                   format_context& ctx) {
     auto out = ctx.out();
     bool first = true;
     for (auto i = n.bigits_.size(); i > 0; --i) {
-      auto value = n.bigits_[i - 1];
+      auto value = n.bigits_[i - 1u];
       if (first) {
         out = format_to(out, "{:x}", value);
         first = false;
@@ -1235,107 +2674,43 @@
       out = format_to(out, "{:08x}", value);
     }
     if (n.exp_ > 0)
-      out = format_to(out, "p{}", n.exp_ * internal::bigint::bigit_bits);
+      out = format_to(out, "p{}", n.exp_ * detail::bigint::bigit_bits);
     return out;
   }
 };
 
-#if FMT_USE_WINDOWS_H
-
-FMT_FUNC internal::utf8_to_utf16::utf8_to_utf16(string_view s) {
-  static const char ERROR_MSG[] = "cannot convert string from UTF-8 to UTF-16";
-  if (s.size() > INT_MAX)
-    FMT_THROW(windows_error(ERROR_INVALID_PARAMETER, ERROR_MSG));
-  int s_size = static_cast<int>(s.size());
-  if (s_size == 0) {
-    // MultiByteToWideChar does not support zero length, handle separately.
-    buffer_.resize(1);
-    buffer_[0] = 0;
-    return;
-  }
-
-  int length = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, s.data(),
-                                   s_size, nullptr, 0);
-  if (length == 0) FMT_THROW(windows_error(GetLastError(), ERROR_MSG));
-  buffer_.resize(length + 1);
-  length = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, s.data(), s_size,
-                               &buffer_[0], length);
-  if (length == 0) FMT_THROW(windows_error(GetLastError(), ERROR_MSG));
-  buffer_[length] = 0;
-}
-
-FMT_FUNC internal::utf16_to_utf8::utf16_to_utf8(wstring_view s) {
-  if (int error_code = convert(s)) {
-    FMT_THROW(windows_error(error_code,
-                            "cannot convert string from UTF-16 to UTF-8"));
-  }
-}
-
-FMT_FUNC int internal::utf16_to_utf8::convert(wstring_view s) {
-  if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;
-  int s_size = static_cast<int>(s.size());
-  if (s_size == 0) {
-    // WideCharToMultiByte does not support zero length, handle separately.
-    buffer_.resize(1);
-    buffer_[0] = 0;
-    return 0;
-  }
-
-  int length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, nullptr, 0,
-                                   nullptr, nullptr);
-  if (length == 0) return GetLastError();
-  buffer_.resize(length + 1);
-  length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, &buffer_[0],
-                               length, nullptr, nullptr);
-  if (length == 0) return GetLastError();
-  buffer_[length] = 0;
-  return 0;
-}
-
-FMT_FUNC void windows_error::init(int err_code, string_view format_str,
-                                  format_args args) {
-  error_code_ = err_code;
-  memory_buffer buffer;
-  internal::format_windows_error(buffer, err_code, vformat(format_str, args));
-  std::runtime_error& base = *this;
-  base = std::runtime_error(to_string(buffer));
-}
-
-FMT_FUNC void internal::format_windows_error(internal::buffer<char>& out,
-                                             int error_code,
-                                             string_view message) FMT_NOEXCEPT {
-  FMT_TRY {
-    wmemory_buffer buf;
-    buf.resize(inline_buffer_size);
-    for (;;) {
-      wchar_t* system_message = &buf[0];
-      int result = FormatMessageW(
-          FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr,
-          error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), system_message,
-          static_cast<uint32_t>(buf.size()), nullptr);
-      if (result != 0) {
-        utf16_to_utf8 utf8_message;
-        if (utf8_message.convert(system_message) == ERROR_SUCCESS) {
-          internal::writer w(out);
-          w.write(message);
-          w.write(": ");
-          w.write(utf8_message);
-          return;
-        }
-        break;
-      }
-      if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
-        break;  // Can't get error message, report error code instead.
-      buf.resize(buf.size() * 2);
+FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
+  auto transcode = [this](const char* p) {
+    auto cp = uint32_t();
+    auto error = 0;
+    p = utf8_decode(p, &cp, &error);
+    if (error != 0) FMT_THROW(std::runtime_error("invalid utf8"));
+    if (cp <= 0xFFFF) {
+      buffer_.push_back(static_cast<wchar_t>(cp));
+    } else {
+      cp -= 0x10000;
+      buffer_.push_back(static_cast<wchar_t>(0xD800 + (cp >> 10)));
+      buffer_.push_back(static_cast<wchar_t>(0xDC00 + (cp & 0x3FF)));
     }
+    return p;
+  };
+  auto p = s.data();
+  const size_t block_size = 4;  // utf8_decode always reads blocks of 4 chars.
+  if (s.size() >= block_size) {
+    for (auto end = p + s.size() - block_size + 1; p < end;) p = transcode(p);
   }
-  FMT_CATCH(...) {}
-  format_error_code(out, error_code, message);
+  if (auto num_chars_left = s.data() + s.size() - p) {
+    char buf[2 * block_size - 1] = {};
+    memcpy(buf, p, to_unsigned(num_chars_left));
+    p = buf;
+    do {
+      p = transcode(p);
+    } while (p - buf < num_chars_left);
+  }
+  buffer_.push_back(0);
 }
 
-#endif  // FMT_USE_WINDOWS_H
-
-FMT_FUNC void format_system_error(internal::buffer<char>& out, int error_code,
+FMT_FUNC void format_system_error(detail::buffer<char>& out, int error_code,
                                   string_view message) FMT_NOEXCEPT {
   FMT_TRY {
     memory_buffer buf;
@@ -1343,12 +2718,10 @@
     for (;;) {
       char* system_message = &buf[0];
       int result =
-          internal::safe_strerror(error_code, system_message, buf.size());
+          detail::safe_strerror(error_code, system_message, buf.size());
       if (result == 0) {
-        internal::writer w(out);
-        w.write(message);
-        w.write(": ");
-        w.write(system_message);
+        format_to(detail::buffer_appender<char>(out), "{}: {}", message,
+                  system_message);
         return;
       }
       if (result != ERANGE)
@@ -1360,7 +2733,7 @@
   format_error_code(out, error_code, message);
 }
 
-FMT_FUNC void internal::error_handler::on_error(const char* message) {
+FMT_FUNC void detail::error_handler::on_error(const char* message) {
   FMT_THROW(format_error(message));
 }
 
@@ -1369,28 +2742,60 @@
   report_error(format_system_error, error_code, message);
 }
 
-#if FMT_USE_WINDOWS_H
-FMT_FUNC void report_windows_error(int error_code,
-                                   fmt::string_view message) FMT_NOEXCEPT {
-  report_error(internal::format_windows_error, error_code, message);
+FMT_FUNC std::string detail::vformat(string_view format_str, format_args args) {
+  if (format_str.size() == 2 && equal2(format_str.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) error_handler().on_error("argument not found");
+    return visit_format_arg(stringifier(), arg);
+  }
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str, args);
+  return to_string(buffer);
 }
+
+#ifdef _WIN32
+namespace detail {
+using dword = conditional_t<sizeof(long) == 4, unsigned long, unsigned>;
+extern "C" __declspec(dllimport) int __stdcall WriteConsoleW(  //
+    void*, const void*, dword, dword*, void*);
+}  // namespace detail
 #endif
 
 FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
   memory_buffer buffer;
-  internal::vformat_to(buffer, format_str,
-                       basic_format_args<buffer_context<char>>(args));
-  internal::fwrite_fully(buffer.data(), 1, buffer.size(), f);
+  detail::vformat_to(buffer, format_str,
+                     basic_format_args<buffer_context<char>>(args));
+#ifdef _WIN32
+  auto fd = _fileno(f);
+  if (_isatty(fd)) {
+    detail::utf8_to_utf16 u16(string_view(buffer.data(), buffer.size()));
+    auto written = detail::dword();
+    if (!detail::WriteConsoleW(reinterpret_cast<void*>(_get_osfhandle(fd)),
+                               u16.c_str(), static_cast<uint32_t>(u16.size()),
+                               &written, nullptr)) {
+      FMT_THROW(format_error("failed to write to console"));
+    }
+    return;
+  }
+#endif
+  detail::fwrite_fully(buffer.data(), 1, buffer.size(), f);
 }
 
+#ifdef _WIN32
+// Print assuming legacy (non-Unicode) encoding.
+FMT_FUNC void detail::vprint_mojibake(std::FILE* f, string_view format_str,
+                                      format_args args) {
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str,
+                     basic_format_args<buffer_context<char>>(args));
+  fwrite_fully(buffer.data(), 1, buffer.size(), f);
+}
+#endif
+
 FMT_FUNC void vprint(string_view format_str, format_args args) {
   vprint(stdout, format_str, args);
 }
 
 FMT_END_NAMESPACE
 
-#ifdef _MSC_VER
-#  pragma warning(pop)
-#endif
-
 #endif  // FMT_FORMAT_INL_H_
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 600b0eb..1a037b0 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -33,8 +33,6 @@
 #ifndef FMT_FORMAT_H_
 #define FMT_FORMAT_H_
 
-#include "core.h"
-
 #include <algorithm>
 #include <cerrno>
 #include <cmath>
@@ -43,11 +41,7 @@
 #include <memory>
 #include <stdexcept>
 
-#ifdef __clang__
-#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
-#else
-#  define FMT_CLANG_VERSION 0
-#endif
+#include "core.h"
 
 #ifdef __INTEL_COMPILER
 #  define FMT_ICC_VERSION __INTEL_COMPILER
@@ -69,26 +63,52 @@
 #  define FMT_HAS_BUILTIN(x) 0
 #endif
 
-#if FMT_HAS_CPP_ATTRIBUTE(fallthrough) >= 201603 && __cplusplus >= 201703
+#if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#  define FMT_NOINLINE __attribute__((noinline))
+#else
+#  define FMT_NOINLINE
+#endif
+
+#if __cplusplus == 201103L || __cplusplus == 201402L
+#  if defined(__INTEL_COMPILER) || defined(__PGI)
+#    define FMT_FALLTHROUGH
+#  elif defined(__clang__)
+#    define FMT_FALLTHROUGH [[clang::fallthrough]]
+#  elif FMT_GCC_VERSION >= 700 && \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 520)
+#    define FMT_FALLTHROUGH [[gnu::fallthrough]]
+#  else
+#    define FMT_FALLTHROUGH
+#  endif
+#elif FMT_HAS_CPP17_ATTRIBUTE(fallthrough) || \
+    (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
 #  define FMT_FALLTHROUGH [[fallthrough]]
 #else
 #  define FMT_FALLTHROUGH
 #endif
 
+#ifndef FMT_MAYBE_UNUSED
+#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
+#    define FMT_MAYBE_UNUSED [[maybe_unused]]
+#  else
+#    define FMT_MAYBE_UNUSED
+#  endif
+#endif
+
 #ifndef FMT_THROW
 #  if FMT_EXCEPTIONS
-#    if FMT_MSC_VER
+#    if FMT_MSC_VER || FMT_NVCC
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 template <typename Exception> inline void do_throw(const Exception& x) {
-  // Silence unreachable code warnings in MSVC because these are nearly
-  // impossible to fix in a generic code.
+  // Silence unreachable code warnings in MSVC and NVCC because these
+  // are nearly impossible to fix in a generic code.
   volatile bool b = true;
   if (b) throw x;
 }
-}  // namespace internal
+}  // namespace detail
 FMT_END_NAMESPACE
-#      define FMT_THROW(x) internal::do_throw(x)
+#      define FMT_THROW(x) detail::do_throw(x)
 #    else
 #      define FMT_THROW(x) throw x
 #    endif
@@ -101,12 +121,19 @@
 #  endif
 #endif
 
+#if FMT_EXCEPTIONS
+#  define FMT_TRY try
+#  define FMT_CATCH(x) catch (x)
+#else
+#  define FMT_TRY if (true)
+#  define FMT_CATCH(x) if (false)
+#endif
+
 #ifndef FMT_USE_USER_DEFINED_LITERALS
-// For Intel and NVIDIA compilers both they and the system gcc/msc support UDLs.
-#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 407 ||      \
-       FMT_MSC_VER >= 1900) &&                                              \
-      (!(FMT_ICC_VERSION || FMT_CUDA_VERSION) || FMT_ICC_VERSION >= 1500 || \
-       FMT_CUDA_VERSION >= 700)
+// EDG based compilers (Intel, NVIDIA, Elbrus, etc), GCC and MSVC support UDLs.
+#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 407 || \
+       FMT_MSC_VER >= 1900) &&                                         \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= /* UDL feature */ 480)
 #    define FMT_USE_USER_DEFINED_LITERALS 1
 #  else
 #    define FMT_USE_USER_DEFINED_LITERALS 0
@@ -114,19 +141,39 @@
 #endif
 
 #ifndef FMT_USE_UDL_TEMPLATE
-// EDG front end based compilers (icc, nvcc) do not support UDL templates yet
-// and GCC 9 warns about them.
-#  if FMT_USE_USER_DEFINED_LITERALS && FMT_ICC_VERSION == 0 && \
-      FMT_CUDA_VERSION == 0 &&                                 \
-      ((FMT_GCC_VERSION >= 600 && FMT_GCC_VERSION <= 900 &&    \
-        __cplusplus >= 201402L) ||                             \
-       FMT_CLANG_VERSION >= 304)
+// EDG frontend based compilers (icc, nvcc, PGI, etc) and GCC < 6.4 do not
+// properly support UDL templates and GCC >= 9 warns about them.
+#  if FMT_USE_USER_DEFINED_LITERALS &&                         \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 501) && \
+      ((FMT_GCC_VERSION >= 604 && __cplusplus >= 201402L) ||   \
+       FMT_CLANG_VERSION >= 304) &&                            \
+      !defined(__PGI) && !defined(__NVCC__)
 #    define FMT_USE_UDL_TEMPLATE 1
 #  else
 #    define FMT_USE_UDL_TEMPLATE 0
 #  endif
 #endif
 
+#ifndef FMT_USE_FLOAT
+#  define FMT_USE_FLOAT 1
+#endif
+
+#ifndef FMT_USE_DOUBLE
+#  define FMT_USE_DOUBLE 1
+#endif
+
+#ifndef FMT_USE_LONG_DOUBLE
+#  define FMT_USE_LONG_DOUBLE 1
+#endif
+
+// Defining FMT_REDUCE_INT_INSTANTIATIONS to 1, will reduce the number of
+// int_writer template instances to just one by only using the largest integer
+// type. This results in a reduction in binary size but will cause a decrease in
+// integer formatting performance.
+#if !defined(FMT_REDUCE_INT_INSTANTIATIONS)
+#  define FMT_REDUCE_INT_INSTANTIATIONS 0
+#endif
+
 // __builtin_clz is broken in clang with Microsoft CodeGen:
 // https://github.com/fmtlib/fmt/issues/519
 #if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clz)) && !FMT_MSC_VER
@@ -135,76 +182,98 @@
 #if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clzll)) && !FMT_MSC_VER
 #  define FMT_BUILTIN_CLZLL(n) __builtin_clzll(n)
 #endif
+#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_ctz))
+#  define FMT_BUILTIN_CTZ(n) __builtin_ctz(n)
+#endif
+#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_ctzll))
+#  define FMT_BUILTIN_CTZLL(n) __builtin_ctzll(n)
+#endif
+
+#if FMT_MSC_VER
+#  include <intrin.h>  // _BitScanReverse[64], _BitScanForward[64], _umul128
+#endif
 
 // Some compilers masquerade as both MSVC and GCC-likes or otherwise support
 // __builtin_clz and __builtin_clzll, so only define FMT_BUILTIN_CLZ using the
 // MSVC intrinsics if the clz and clzll builtins are not available.
-#if FMT_MSC_VER && !defined(FMT_BUILTIN_CLZLL) && !defined(_MANAGED)
-#  include <intrin.h>  // _BitScanReverse, _BitScanReverse64
-
+#if FMT_MSC_VER && !defined(FMT_BUILTIN_CLZLL) && \
+    !defined(FMT_BUILTIN_CTZLL) && !defined(_MANAGED)
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 // Avoid Clang with Microsoft CodeGen's -Wunknown-pragmas warning.
 #  ifndef __clang__
+#    pragma intrinsic(_BitScanForward)
 #    pragma intrinsic(_BitScanReverse)
 #  endif
-inline uint32_t clz(uint32_t x) {
+#  if defined(_WIN64) && !defined(__clang__)
+#    pragma intrinsic(_BitScanForward64)
+#    pragma intrinsic(_BitScanReverse64)
+#  endif
+
+inline int clz(uint32_t x) {
   unsigned long r = 0;
   _BitScanReverse(&r, x);
-
   FMT_ASSERT(x != 0, "");
   // Static analysis complains about using uninitialized data
   // "r", but the only way that can happen is if "x" is 0,
   // which the callers guarantee to not happen.
-#  pragma warning(suppress : 6102)
-  return 31 - r;
+  FMT_SUPPRESS_MSC_WARNING(6102)
+  return 31 ^ static_cast<int>(r);
 }
-#  define FMT_BUILTIN_CLZ(n) internal::clz(n)
+#  define FMT_BUILTIN_CLZ(n) detail::clz(n)
 
-#  if defined(_WIN64) && !defined(__clang__)
-#    pragma intrinsic(_BitScanReverse64)
-#  endif
-
-inline uint32_t clzll(uint64_t x) {
+inline int clzll(uint64_t x) {
   unsigned long r = 0;
 #  ifdef _WIN64
   _BitScanReverse64(&r, x);
 #  else
   // Scan the high 32 bits.
-  if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32))) return 63 - (r + 32);
-
+  if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32))) return 63 ^ (r + 32);
   // Scan the low 32 bits.
   _BitScanReverse(&r, static_cast<uint32_t>(x));
 #  endif
-
   FMT_ASSERT(x != 0, "");
-  // Static analysis complains about using uninitialized data
-  // "r", but the only way that can happen is if "x" is 0,
-  // which the callers guarantee to not happen.
-#  pragma warning(suppress : 6102)
-  return 63 - r;
+  FMT_SUPPRESS_MSC_WARNING(6102)  // Suppress a bogus static analysis warning.
+  return 63 ^ static_cast<int>(r);
 }
-#  define FMT_BUILTIN_CLZLL(n) internal::clzll(n)
-}  // namespace internal
+#  define FMT_BUILTIN_CLZLL(n) detail::clzll(n)
+
+inline int ctz(uint32_t x) {
+  unsigned long r = 0;
+  _BitScanForward(&r, x);
+  FMT_ASSERT(x != 0, "");
+  FMT_SUPPRESS_MSC_WARNING(6102)  // Suppress a bogus static analysis warning.
+  return static_cast<int>(r);
+}
+#  define FMT_BUILTIN_CTZ(n) detail::ctz(n)
+
+inline int ctzll(uint64_t x) {
+  unsigned long r = 0;
+  FMT_ASSERT(x != 0, "");
+  FMT_SUPPRESS_MSC_WARNING(6102)  // Suppress a bogus static analysis warning.
+#  ifdef _WIN64
+  _BitScanForward64(&r, x);
+#  else
+  // Scan the low 32 bits.
+  if (_BitScanForward(&r, static_cast<uint32_t>(x))) return static_cast<int>(r);
+  // Scan the high 32 bits.
+  _BitScanForward(&r, static_cast<uint32_t>(x >> 32));
+  r += 32;
+#  endif
+  return static_cast<int>(r);
+}
+#  define FMT_BUILTIN_CTZLL(n) detail::ctzll(n)
+}  // namespace detail
 FMT_END_NAMESPACE
 #endif
 
 // Enable the deprecated numeric alignment.
-#ifndef FMT_NUMERIC_ALIGN
-#  define FMT_NUMERIC_ALIGN 1
-#endif
-
-// Enable the deprecated percent specifier.
-#ifndef FMT_DEPRECATED_PERCENT
-#  define FMT_DEPRECATED_PERCENT 0
+#ifndef FMT_DEPRECATED_NUMERIC_ALIGN
+#  define FMT_DEPRECATED_NUMERIC_ALIGN 0
 #endif
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
-
-// A helper function to suppress bogus "conditional expression is constant"
-// warnings.
-template <typename T> inline T const_check(T value) { return value; }
+namespace detail {
 
 // An equivalent of `*reinterpret_cast<Dest*>(&source)` that doesn't have
 // undefined behavior (e.g. due to type aliasing).
@@ -218,7 +287,7 @@
 }
 
 inline bool is_big_endian() {
-  auto u = 1u;
+  const auto u = 1u;
   struct bytes {
     char data[sizeof(u)];
   };
@@ -256,47 +325,25 @@
 template <typename T> constexpr int num_bits() {
   return std::numeric_limits<T>::digits;
 }
+// std::numeric_limits<T>::digits may return 0 for 128-bit ints.
+template <> constexpr int num_bits<int128_t>() { return 128; }
+template <> constexpr int num_bits<uint128_t>() { return 128; }
 template <> constexpr int num_bits<fallback_uintptr>() {
   return static_cast<int>(sizeof(void*) *
                           std::numeric_limits<unsigned char>::digits);
 }
 
+FMT_INLINE void assume(bool condition) {
+  (void)condition;
+#if FMT_HAS_BUILTIN(__builtin_assume)
+  __builtin_assume(condition);
+#endif
+}
+
 // An approximation of iterator_t for pre-C++20 systems.
 template <typename T>
 using iterator_t = decltype(std::begin(std::declval<T&>()));
-
-// Detect the iterator category of *any* given type in a SFINAE-friendly way.
-// Unfortunately, older implementations of std::iterator_traits are not safe
-// for use in a SFINAE-context.
-template <typename It, typename Enable = void>
-struct iterator_category : std::false_type {};
-
-template <typename T> struct iterator_category<T*> {
-  using type = std::random_access_iterator_tag;
-};
-
-template <typename It>
-struct iterator_category<It, void_t<typename It::iterator_category>> {
-  using type = typename It::iterator_category;
-};
-
-// Detect if *any* given type models the OutputIterator concept.
-template <typename It> class is_output_iterator {
-  // Check for mutability because all iterator categories derived from
-  // std::input_iterator_tag *may* also meet the requirements of an
-  // OutputIterator, thereby falling into the category of 'mutable iterators'
-  // [iterator.requirements.general] clause 4. The compiler reveals this
-  // property only at the point of *actually dereferencing* the iterator!
-  template <typename U>
-  static decltype(*(std::declval<U>())) test(std::input_iterator_tag);
-  template <typename U> static char& test(std::output_iterator_tag);
-  template <typename U> static const char& test(...);
-
-  using type = decltype(test<It>(typename iterator_category<It>::type{}));
-
- public:
-  static const bool value = !std::is_const<remove_reference_t<type>>::value;
-};
+template <typename T> using sentinel_t = decltype(std::end(std::declval<T&>()));
 
 // A workaround for std::string not having mutable data() until C++17.
 template <typename Char> inline Char* get_data(std::basic_string<Char>& s) {
@@ -307,28 +354,61 @@
   return c.data();
 }
 
-#ifdef _SECURE_SCL
+#if defined(_SECURE_SCL) && _SECURE_SCL
 // Make a checked iterator to avoid MSVC warnings.
 template <typename T> using checked_ptr = stdext::checked_array_iterator<T*>;
-template <typename T> checked_ptr<T> make_checked(T* p, std::size_t size) {
+template <typename T> checked_ptr<T> make_checked(T* p, size_t size) {
   return {p, size};
 }
 #else
 template <typename T> using checked_ptr = T*;
-template <typename T> inline T* make_checked(T* p, std::size_t) { return p; }
+template <typename T> inline T* make_checked(T* p, size_t) { return p; }
 #endif
 
 template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
-inline checked_ptr<typename Container::value_type> reserve(
-    std::back_insert_iterator<Container>& it, std::size_t n) {
+#if FMT_CLANG_VERSION
+__attribute__((no_sanitize("undefined")))
+#endif
+inline checked_ptr<typename Container::value_type>
+reserve(std::back_insert_iterator<Container> it, size_t n) {
   Container& c = get_container(it);
-  std::size_t size = c.size();
+  size_t size = c.size();
   c.resize(size + n);
   return make_checked(get_data(c) + size, n);
 }
 
+template <typename T>
+inline buffer_appender<T> reserve(buffer_appender<T> it, size_t n) {
+  buffer<T>& buf = get_container(it);
+  buf.try_reserve(buf.size() + n);
+  return it;
+}
+
+template <typename Iterator> inline Iterator& reserve(Iterator& it, size_t) {
+  return it;
+}
+
+template <typename T, typename OutputIt>
+constexpr T* to_pointer(OutputIt, size_t) {
+  return nullptr;
+}
+template <typename T> T* to_pointer(buffer_appender<T> it, size_t n) {
+  buffer<T>& buf = get_container(it);
+  auto size = buf.size();
+  if (buf.capacity() < size + n) return nullptr;
+  buf.try_resize(size + n);
+  return buf.data() + size;
+}
+
+template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
+inline std::back_insert_iterator<Container> base_iterator(
+    std::back_insert_iterator<Container>& it,
+    checked_ptr<typename Container::value_type>) {
+  return it;
+}
+
 template <typename Iterator>
-inline Iterator& reserve(Iterator& it, std::size_t) {
+inline Iterator base_iterator(Iterator, Iterator it) {
   return it;
 }
 
@@ -336,7 +416,7 @@
 // discards them.
 class counting_iterator {
  private:
-  std::size_t count_;
+  size_t count_;
 
  public:
   using iterator_category = std::output_iterator_tag;
@@ -351,33 +431,38 @@
 
   counting_iterator() : count_(0) {}
 
-  std::size_t count() const { return count_; }
+  size_t count() const { return count_; }
 
   counting_iterator& operator++() {
     ++count_;
     return *this;
   }
-
   counting_iterator operator++(int) {
     auto it = *this;
     ++*this;
     return it;
   }
 
+  friend counting_iterator operator+(counting_iterator it, difference_type n) {
+    it.count_ += static_cast<size_t>(n);
+    return it;
+  }
+
   value_type operator*() const { return {}; }
 };
 
 template <typename OutputIt> class truncating_iterator_base {
  protected:
   OutputIt out_;
-  std::size_t limit_;
-  std::size_t count_;
+  size_t limit_;
+  size_t count_;
 
-  truncating_iterator_base(OutputIt out, std::size_t limit)
+  truncating_iterator_base(OutputIt out, size_t limit)
       : out_(out), limit_(limit), count_(0) {}
 
  public:
   using iterator_category = std::output_iterator_tag;
+  using value_type = typename std::iterator_traits<OutputIt>::value_type;
   using difference_type = void;
   using pointer = void;
   using reference = void;
@@ -385,7 +470,7 @@
       truncating_iterator_base;  // Mark iterator as checked.
 
   OutputIt base() const { return out_; }
-  std::size_t count() const { return count_; }
+  size_t count() const { return count_; }
 };
 
 // An output iterator that truncates the output and counts the number of objects
@@ -398,14 +483,12 @@
 template <typename OutputIt>
 class truncating_iterator<OutputIt, std::false_type>
     : public truncating_iterator_base<OutputIt> {
-  using traits = std::iterator_traits<OutputIt>;
-
-  mutable typename traits::value_type blackhole_;
+  mutable typename truncating_iterator_base<OutputIt>::value_type blackhole_;
 
  public:
-  using value_type = typename traits::value_type;
+  using value_type = typename truncating_iterator_base<OutputIt>::value_type;
 
-  truncating_iterator(OutputIt out, std::size_t limit)
+  truncating_iterator(OutputIt out, size_t limit)
       : truncating_iterator_base<OutputIt>(out, limit) {}
 
   truncating_iterator& operator++() {
@@ -428,13 +511,11 @@
 class truncating_iterator<OutputIt, std::true_type>
     : public truncating_iterator_base<OutputIt> {
  public:
-  using value_type = typename OutputIt::container_type::value_type;
-
-  truncating_iterator(OutputIt out, std::size_t limit)
+  truncating_iterator(OutputIt out, size_t limit)
       : truncating_iterator_base<OutputIt>(out, limit) {}
 
-  truncating_iterator& operator=(value_type val) {
-    if (this->count_++ < this->limit_) this->out_ = val;
+  template <typename T> truncating_iterator& operator=(T val) {
+    if (this->count_++ < this->limit_) *this->out_++ = val;
     return *this;
   }
 
@@ -443,30 +524,14 @@
   truncating_iterator& operator*() { return *this; }
 };
 
-// A range with the specified output iterator and value type.
-template <typename OutputIt, typename T = typename OutputIt::value_type>
-class output_range {
- private:
-  OutputIt it_;
-
- public:
-  using value_type = T;
-  using iterator = OutputIt;
-  struct sentinel {};
-
-  explicit output_range(OutputIt it) : it_(it) {}
-  OutputIt begin() const { return it_; }
-  sentinel end() const { return {}; }  // Sentinel is not used yet.
-};
-
 template <typename Char>
 inline size_t count_code_points(basic_string_view<Char> s) {
   return s.size();
 }
 
 // Counts the number of code points in a UTF-8 string.
-inline size_t count_code_points(basic_string_view<char8_t> s) {
-  const char8_t* data = s.data();
+inline size_t count_code_points(basic_string_view<char> s) {
+  const char* data = s.data();
   size_t num_code_points = 0;
   for (size_t i = 0, size = s.size(); i != size; ++i) {
     if ((data[i] & 0xc0) != 0x80) ++num_code_points;
@@ -474,6 +539,11 @@
   return num_code_points;
 }
 
+inline size_t count_code_points(basic_string_view<char8_type> s) {
+  return count_code_points(basic_string_view<char>(
+      reinterpret_cast<const char*>(s.data()), s.size()));
+}
+
 template <typename Char>
 inline size_t code_point_index(basic_string_view<Char> s, size_t n) {
   size_t size = s.size();
@@ -481,8 +551,8 @@
 }
 
 // Calculates the index of the nth code point in a UTF-8 string.
-inline size_t code_point_index(basic_string_view<char8_t> s, size_t n) {
-  const char8_t* data = s.data();
+inline size_t code_point_index(basic_string_view<char8_type> s, size_t n) {
+  const char8_type* data = s.data();
   size_t num_code_points = 0;
   for (size_t i = 0, size = s.size(); i != size; ++i) {
     if ((data[i] & 0xc0) != 0x80 && ++num_code_points > n) {
@@ -492,13 +562,11 @@
   return s.size();
 }
 
-inline char8_t to_char8_t(char c) { return static_cast<char8_t>(c); }
-
 template <typename InputIt, typename OutChar>
 using needs_conversion = bool_constant<
     std::is_same<typename std::iterator_traits<InputIt>::value_type,
                  char>::value &&
-    std::is_same<OutChar, char8_t>::value>;
+    std::is_same<OutChar, char8_type>::value>;
 
 template <typename OutChar, typename InputIt, typename OutputIt,
           FMT_ENABLE_IF(!needs_conversion<InputIt, OutChar>::value)>
@@ -509,56 +577,44 @@
 template <typename OutChar, typename InputIt, typename OutputIt,
           FMT_ENABLE_IF(needs_conversion<InputIt, OutChar>::value)>
 OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
-  return std::transform(begin, end, it, to_char8_t);
+  return std::transform(begin, end, it,
+                        [](char c) { return static_cast<char8_type>(c); });
 }
 
-#ifndef FMT_USE_GRISU
-#  define FMT_USE_GRISU 1
+template <typename Char, typename InputIt>
+inline counting_iterator copy_str(InputIt begin, InputIt end,
+                                  counting_iterator it) {
+  return it + (end - begin);
+}
+
+template <typename T>
+using is_fast_float = bool_constant<std::numeric_limits<T>::is_iec559 &&
+                                    sizeof(T) <= sizeof(double)>;
+
+#ifndef FMT_USE_FULL_CACHE_DRAGONBOX
+#  define FMT_USE_FULL_CACHE_DRAGONBOX 0
 #endif
 
-template <typename T> constexpr bool use_grisu() {
-  return FMT_USE_GRISU && std::numeric_limits<double>::is_iec559 &&
-         sizeof(T) <= sizeof(double);
-}
-
 template <typename T>
 template <typename U>
 void buffer<T>::append(const U* begin, const U* end) {
-  std::size_t new_size = size_ + to_unsigned(end - begin);
-  reserve(new_size);
-  std::uninitialized_copy(begin, end, make_checked(ptr_, capacity_) + size_);
-  size_ = new_size;
+  do {
+    auto count = to_unsigned(end - begin);
+    try_reserve(size_ + count);
+    auto free_cap = capacity_ - size_;
+    if (free_cap < count) count = free_cap;
+    std::uninitialized_copy_n(begin, count, make_checked(ptr_ + size_, count));
+    size_ += count;
+    begin += count;
+  } while (begin != end);
 }
-}  // namespace internal
 
-// A range with an iterator appending to a buffer.
-template <typename T>
-class buffer_range : public internal::output_range<
-                         std::back_insert_iterator<internal::buffer<T>>, T> {
- public:
-  using iterator = std::back_insert_iterator<internal::buffer<T>>;
-  using internal::output_range<iterator, T>::output_range;
-  buffer_range(internal::buffer<T>& buf)
-      : internal::output_range<iterator, T>(std::back_inserter(buf)) {}
-};
-
-// A UTF-8 string view.
-class u8string_view : public basic_string_view<char8_t> {
- public:
-  u8string_view(const char* s)
-      : basic_string_view<char8_t>(reinterpret_cast<const char8_t*>(s)) {}
-  u8string_view(const char* s, size_t count) FMT_NOEXCEPT
-      : basic_string_view<char8_t>(reinterpret_cast<const char8_t*>(s), count) {
-  }
-};
-
-#if FMT_USE_USER_DEFINED_LITERALS
-inline namespace literals {
-inline u8string_view operator"" _u(const char* s, std::size_t n) {
-  return {s, n};
+template <typename OutputIt, typename T, typename Traits>
+void iterator_buffer<OutputIt, T, Traits>::flush() {
+  out_ = std::copy_n(data_, this->limit(this->size()), out_);
+  this->clear();
 }
-}  // namespace literals
-#endif
+}  // namespace detail
 
 // The number of characters to store in the basic_memory_buffer object itself
 // to avoid dynamic memory allocation.
@@ -593,42 +649,44 @@
   The output can be converted to an ``std::string`` with ``to_string(out)``.
   \endrst
  */
-template <typename T, std::size_t SIZE = inline_buffer_size,
+template <typename T, size_t SIZE = inline_buffer_size,
           typename Allocator = std::allocator<T>>
-class basic_memory_buffer : private Allocator, public internal::buffer<T> {
+class basic_memory_buffer final : public detail::buffer<T> {
  private:
   T store_[SIZE];
 
+  // Don't inherit from Allocator avoid generating type_info for it.
+  Allocator alloc_;
+
   // Deallocate memory allocated by the buffer.
   void deallocate() {
     T* data = this->data();
-    if (data != store_) Allocator::deallocate(data, this->capacity());
+    if (data != store_) alloc_.deallocate(data, this->capacity());
   }
 
  protected:
-  void grow(std::size_t size) FMT_OVERRIDE;
+  void grow(size_t size) final FMT_OVERRIDE;
 
  public:
   using value_type = T;
   using const_reference = const T&;
 
   explicit basic_memory_buffer(const Allocator& alloc = Allocator())
-      : Allocator(alloc) {
+      : alloc_(alloc) {
     this->set(store_, SIZE);
   }
-  ~basic_memory_buffer() FMT_OVERRIDE { deallocate(); }
+  ~basic_memory_buffer() { deallocate(); }
 
  private:
   // Move data from other to this buffer.
   void move(basic_memory_buffer& other) {
-    Allocator &this_alloc = *this, &other_alloc = other;
-    this_alloc = std::move(other_alloc);
+    alloc_ = std::move(other.alloc_);
     T* data = other.data();
-    std::size_t size = other.size(), capacity = other.capacity();
+    size_t size = other.size(), capacity = other.capacity();
     if (data == other.store_) {
       this->set(store_, capacity);
       std::uninitialized_copy(other.store_, other.store_ + size,
-                              internal::make_checked(store_, capacity));
+                              detail::make_checked(store_, capacity));
     } else {
       this->set(data, capacity);
       // Set pointer to the inline array so that delete is not called
@@ -660,33 +718,55 @@
   }
 
   // Returns a copy of the allocator associated with this buffer.
-  Allocator get_allocator() const { return *this; }
+  Allocator get_allocator() const { return alloc_; }
+
+  /**
+    Resizes the buffer to contain *count* elements. If T is a POD type new
+    elements may not be initialized.
+   */
+  void resize(size_t count) { this->try_resize(count); }
+
+  /** Increases the buffer capacity to *new_capacity*. */
+  void reserve(size_t new_capacity) { this->try_reserve(new_capacity); }
+
+  // Directly append data into the buffer
+  using detail::buffer<T>::append;
+  template <typename ContiguousRange>
+  void append(const ContiguousRange& range) {
+    append(range.data(), range.data() + range.size());
+  }
 };
 
-template <typename T, std::size_t SIZE, typename Allocator>
-void basic_memory_buffer<T, SIZE, Allocator>::grow(std::size_t size) {
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-  if (size > 1000) throw std::runtime_error("fuzz mode - won't grow that much");
+template <typename T, size_t SIZE, typename Allocator>
+void basic_memory_buffer<T, SIZE, Allocator>::grow(size_t size) {
+#ifdef FMT_FUZZ
+  if (size > 5000) throw std::runtime_error("fuzz mode - won't grow that much");
 #endif
-  std::size_t old_capacity = this->capacity();
-  std::size_t new_capacity = old_capacity + old_capacity / 2;
+  size_t old_capacity = this->capacity();
+  size_t new_capacity = old_capacity + old_capacity / 2;
   if (size > new_capacity) new_capacity = size;
   T* old_data = this->data();
-  T* new_data = std::allocator_traits<Allocator>::allocate(*this, new_capacity);
+  T* new_data =
+      std::allocator_traits<Allocator>::allocate(alloc_, new_capacity);
   // The following code doesn't throw, so the raw pointer above doesn't leak.
   std::uninitialized_copy(old_data, old_data + this->size(),
-                          internal::make_checked(new_data, new_capacity));
+                          detail::make_checked(new_data, new_capacity));
   this->set(new_data, new_capacity);
   // deallocate must not throw according to the standard, but even if it does,
   // the buffer already uses the new storage and will deallocate it in
   // destructor.
-  if (old_data != store_) Allocator::deallocate(old_data, old_capacity);
+  if (old_data != store_) alloc_.deallocate(old_data, old_capacity);
 }
 
 using memory_buffer = basic_memory_buffer<char>;
 using wmemory_buffer = basic_memory_buffer<wchar_t>;
 
+template <typename T, size_t SIZE, typename Allocator>
+struct is_contiguous<basic_memory_buffer<T, SIZE, Allocator>> : std::true_type {
+};
+
 /** A formatting error such as invalid format string. */
+FMT_CLASS_API
 class FMT_API format_error : public std::runtime_error {
  public:
   explicit format_error(const char* message) : std::runtime_error(message) {}
@@ -699,43 +779,138 @@
   ~format_error() FMT_NOEXCEPT FMT_OVERRIDE;
 };
 
-namespace internal {
+namespace detail {
+
+template <typename T>
+using is_signed =
+    std::integral_constant<bool, std::numeric_limits<T>::is_signed ||
+                                     std::is_same<T, int128_t>::value>;
 
 // Returns true if value is negative, false otherwise.
 // Same as `value < 0` but doesn't produce warnings if T is an unsigned type.
-template <typename T, FMT_ENABLE_IF(std::numeric_limits<T>::is_signed)>
+template <typename T, FMT_ENABLE_IF(is_signed<T>::value)>
 FMT_CONSTEXPR bool is_negative(T value) {
   return value < 0;
 }
-template <typename T, FMT_ENABLE_IF(!std::numeric_limits<T>::is_signed)>
+template <typename T, FMT_ENABLE_IF(!is_signed<T>::value)>
 FMT_CONSTEXPR bool is_negative(T) {
   return false;
 }
 
+template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+FMT_CONSTEXPR bool is_supported_floating_point(T) {
+  return (std::is_same<T, float>::value && FMT_USE_FLOAT) ||
+         (std::is_same<T, double>::value && FMT_USE_DOUBLE) ||
+         (std::is_same<T, long double>::value && FMT_USE_LONG_DOUBLE);
+}
+
 // Smallest of uint32_t, uint64_t, uint128_t that is large enough to
-// represent all values of T.
+// represent all values of an integral type T.
 template <typename T>
-using uint32_or_64_or_128_t = conditional_t<
-    std::numeric_limits<T>::digits <= 32, uint32_t,
-    conditional_t<std::numeric_limits<T>::digits <= 64, uint64_t, uint128_t>>;
+using uint32_or_64_or_128_t =
+    conditional_t<num_bits<T>() <= 32 && !FMT_REDUCE_INT_INSTANTIATIONS,
+                  uint32_t,
+                  conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
+
+// 128-bit integer type used internally
+struct FMT_EXTERN_TEMPLATE_API uint128_wrapper {
+  uint128_wrapper() = default;
+
+#if FMT_USE_INT128
+  uint128_t internal_;
+
+  uint128_wrapper(uint64_t high, uint64_t low) FMT_NOEXCEPT
+      : internal_{static_cast<uint128_t>(low) |
+                  (static_cast<uint128_t>(high) << 64)} {}
+
+  uint128_wrapper(uint128_t u) : internal_{u} {}
+
+  uint64_t high() const FMT_NOEXCEPT { return uint64_t(internal_ >> 64); }
+  uint64_t low() const FMT_NOEXCEPT { return uint64_t(internal_); }
+
+  uint128_wrapper& operator+=(uint64_t n) FMT_NOEXCEPT {
+    internal_ += n;
+    return *this;
+  }
+#else
+  uint64_t high_;
+  uint64_t low_;
+
+  uint128_wrapper(uint64_t high, uint64_t low) FMT_NOEXCEPT : high_{high},
+                                                              low_{low} {}
+
+  uint64_t high() const FMT_NOEXCEPT { return high_; }
+  uint64_t low() const FMT_NOEXCEPT { return low_; }
+
+  uint128_wrapper& operator+=(uint64_t n) FMT_NOEXCEPT {
+#  if defined(_MSC_VER) && defined(_M_X64)
+    unsigned char carry = _addcarry_u64(0, low_, n, &low_);
+    _addcarry_u64(carry, high_, 0, &high_);
+    return *this;
+#  else
+    uint64_t sum = low_ + n;
+    high_ += (sum < low_ ? 1 : 0);
+    low_ = sum;
+    return *this;
+#  endif
+  }
+#endif
+};
+
+// Table entry type for divisibility test used internally
+template <typename T> struct FMT_EXTERN_TEMPLATE_API divtest_table_entry {
+  T mod_inv;
+  T max_quotient;
+};
 
 // Static data is placed in this class template for the header-only config.
 template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
   static const uint64_t powers_of_10_64[];
-  static const uint32_t zero_or_powers_of_10_32[];
-  static const uint64_t zero_or_powers_of_10_64[];
-  static const uint64_t pow10_significands[];
-  static const int16_t pow10_exponents[];
-  static const char digits[];
+  static const uint32_t zero_or_powers_of_10_32_new[];
+  static const uint64_t zero_or_powers_of_10_64_new[];
+  static const uint64_t grisu_pow10_significands[];
+  static const int16_t grisu_pow10_exponents[];
+  static const divtest_table_entry<uint32_t> divtest_table_for_pow5_32[];
+  static const divtest_table_entry<uint64_t> divtest_table_for_pow5_64[];
+  static const uint64_t dragonbox_pow10_significands_64[];
+  static const uint128_wrapper dragonbox_pow10_significands_128[];
+  // log10(2) = 0x0.4d104d427de7fbcc...
+  static const uint64_t log10_2_significand = 0x4d104d427de7fbcc;
+#if !FMT_USE_FULL_CACHE_DRAGONBOX
+  static const uint64_t powers_of_5_64[];
+  static const uint32_t dragonbox_pow10_recovery_errors[];
+#endif
+  // GCC generates slightly better code for pairs than chars.
+  using digit_pair = char[2];
+  static const digit_pair digits[];
   static const char hex_digits[];
   static const char foreground_color[];
   static const char background_color[];
   static const char reset_color[5];
   static const wchar_t wreset_color[5];
   static const char signs[];
+  static const char left_padding_shifts[5];
+  static const char right_padding_shifts[5];
+
+  // DEPRECATED! These are for ABI compatibility.
+  static const uint32_t zero_or_powers_of_10_32[];
+  static const uint64_t zero_or_powers_of_10_64[];
 };
 
+// Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
+// This is a function instead of an array to workaround a bug in GCC10 (#1810).
+FMT_INLINE uint16_t bsr2log10(int bsr) {
+  static constexpr uint16_t data[] = {
+      1,  1,  1,  2,  2,  2,  3,  3,  3,  4,  4,  4,  4,  5,  5,  5,
+      6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9,  10, 10, 10,
+      10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
+      15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
+  return data[bsr];
+}
+
+#ifndef FMT_EXPORTED
 FMT_EXTERN template struct basic_data<void>;
+#endif
 
 // This is a struct rather than an alias to avoid shadowing warnings in gcc.
 struct data : basic_data<> {};
@@ -744,10 +919,9 @@
 // Returns the number of decimal digits in n. Leading zeros are not counted
 // except for n == 0 in which case count_digits returns 1.
 inline int count_digits(uint64_t n) {
-  // Based on http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
-  // and the benchmark https://github.com/localvoid/cxx-benchmark-count-digits.
-  int t = (64 - FMT_BUILTIN_CLZLL(n | 1)) * 1233 >> 12;
-  return t - (n < data::zero_or_powers_of_10_64[t]) + 1;
+  // https://github.com/fmtlib/format-benchmark/blob/master/digits10
+  auto t = bsr2log10(FMT_BUILTIN_CLZLL(n | 1) ^ 63);
+  return t - (n < data::zero_or_powers_of_10_64_new[t]);
 }
 #else
 // Fallback version of count_digits used when __builtin_clz is not available.
@@ -793,76 +967,37 @@
   return num_digits;
 }
 
-template <> int count_digits<4>(internal::fallback_uintptr n);
+template <> int count_digits<4>(detail::fallback_uintptr n);
 
 #if FMT_GCC_VERSION || FMT_CLANG_VERSION
 #  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
+#elif FMT_MSC_VER
+#  define FMT_ALWAYS_INLINE __forceinline
 #else
-#  define FMT_ALWAYS_INLINE
+#  define FMT_ALWAYS_INLINE inline
 #endif
 
-// Computes g = floor(log10(n)) and calls h.on<g>(n);
-template <typename Handler> FMT_ALWAYS_INLINE char* lg(uint32_t n, Handler h) {
-  return n < 100 ? n < 10 ? h.template on<0>(n) : h.template on<1>(n)
-                 : n < 1000000
-                       ? n < 10000 ? n < 1000 ? h.template on<2>(n)
-                                              : h.template on<3>(n)
-                                   : n < 100000 ? h.template on<4>(n)
-                                                : h.template on<5>(n)
-                       : n < 100000000 ? n < 10000000 ? h.template on<6>(n)
-                                                      : h.template on<7>(n)
-                                       : n < 1000000000 ? h.template on<8>(n)
-                                                        : h.template on<9>(n);
-}
-
-// An lg handler that formats a decimal number.
-// Usage: lg(n, decimal_formatter(buffer));
-class decimal_formatter {
- private:
-  char* buffer_;
-
-  void write_pair(unsigned N, uint32_t index) {
-    std::memcpy(buffer_ + N, data::digits + index * 2, 2);
-  }
-
- public:
-  explicit decimal_formatter(char* buf) : buffer_(buf) {}
-
-  template <unsigned N> char* on(uint32_t u) {
-    if (N == 0) {
-      *buffer_ = static_cast<char>(u) + '0';
-    } else if (N == 1) {
-      write_pair(0, u);
-    } else {
-      // The idea of using 4.32 fixed-point numbers is based on
-      // https://github.com/jeaiii/itoa
-      unsigned n = N - 1;
-      unsigned a = n / 5 * n * 53 / 16;
-      uint64_t t =
-          ((1ULL << (32 + a)) / data::zero_or_powers_of_10_32[n] + 1 - n / 9);
-      t = ((t * u) >> a) + n / 5 * 4;
-      write_pair(0, t >> 32);
-      for (unsigned i = 2; i < N; i += 2) {
-        t = 100ULL * static_cast<uint32_t>(t);
-        write_pair(i, t >> 32);
-      }
-      if (N % 2 == 0) {
-        buffer_[N] =
-            static_cast<char>((10ULL * static_cast<uint32_t>(t)) >> 32) + '0';
-      }
-    }
-    return buffer_ += N + 1;
-  }
-};
+// To suppress unnecessary security cookie checks
+#if FMT_MSC_VER && !FMT_CLANG_VERSION
+#  define FMT_SAFEBUFFERS __declspec(safebuffers)
+#else
+#  define FMT_SAFEBUFFERS
+#endif
 
 #ifdef FMT_BUILTIN_CLZ
 // Optional version of count_digits for better performance on 32-bit platforms.
 inline int count_digits(uint32_t n) {
-  int t = (32 - FMT_BUILTIN_CLZ(n | 1)) * 1233 >> 12;
-  return t - (n < data::zero_or_powers_of_10_32[t]) + 1;
+  auto t = bsr2log10(FMT_BUILTIN_CLZ(n | 1) ^ 31);
+  return t - (n < data::zero_or_powers_of_10_32_new[t]);
 }
 #endif
 
+template <typename Int> constexpr int digits10() FMT_NOEXCEPT {
+  return std::numeric_limits<Int>::digits10;
+}
+template <> constexpr int digits10<int128_t>() FMT_NOEXCEPT { return 38; }
+template <> constexpr int digits10<uint128_t>() FMT_NOEXCEPT { return 38; }
+
 template <typename Char> FMT_API std::string grouping_impl(locale_ref loc);
 template <typename Char> inline std::string grouping(locale_ref loc) {
   return grouping_impl<char>(loc);
@@ -887,57 +1022,60 @@
   return decimal_point_impl<wchar_t>(loc);
 }
 
-// Formats a decimal unsigned integer value writing into buffer.
-// add_thousands_sep is called after writing each char to add a thousands
-// separator if necessary.
-template <typename UInt, typename Char, typename F>
-inline Char* format_decimal(Char* buffer, UInt value, int num_digits,
-                            F add_thousands_sep) {
-  FMT_ASSERT(num_digits >= 0, "invalid digit count");
-  buffer += num_digits;
-  Char* end = buffer;
+// Compares two characters for equality.
+template <typename Char> bool equal2(const Char* lhs, const char* rhs) {
+  return lhs[0] == rhs[0] && lhs[1] == rhs[1];
+}
+inline bool equal2(const char* lhs, const char* rhs) {
+  return memcmp(lhs, rhs, 2) == 0;
+}
+
+// Copies two characters from src to dst.
+template <typename Char> void copy2(Char* dst, const char* src) {
+  *dst++ = static_cast<Char>(*src++);
+  *dst = static_cast<Char>(*src);
+}
+FMT_INLINE void copy2(char* dst, const char* src) { memcpy(dst, src, 2); }
+
+template <typename Iterator> struct format_decimal_result {
+  Iterator begin;
+  Iterator end;
+};
+
+// Formats a decimal unsigned integer value writing into out pointing to a
+// buffer of specified size. The caller must ensure that the buffer is large
+// enough.
+template <typename Char, typename UInt>
+inline format_decimal_result<Char*> format_decimal(Char* out, UInt value,
+                                                   int size) {
+  FMT_ASSERT(size >= count_digits(value), "invalid digit count");
+  out += size;
+  Char* end = out;
   while (value >= 100) {
     // Integer division is slow so do it for a group of two digits instead
     // of for every digit. The idea comes from the talk by Alexandrescu
     // "Three Optimization Tips for C++". See speed-test for a comparison.
-    auto index = static_cast<unsigned>((value % 100) * 2);
+    out -= 2;
+    copy2(out, data::digits[value % 100]);
     value /= 100;
-    *--buffer = static_cast<Char>(data::digits[index + 1]);
-    add_thousands_sep(buffer);
-    *--buffer = static_cast<Char>(data::digits[index]);
-    add_thousands_sep(buffer);
   }
   if (value < 10) {
-    *--buffer = static_cast<Char>('0' + value);
-    return end;
+    *--out = static_cast<Char>('0' + value);
+    return {out, end};
   }
-  auto index = static_cast<unsigned>(value * 2);
-  *--buffer = static_cast<Char>(data::digits[index + 1]);
-  add_thousands_sep(buffer);
-  *--buffer = static_cast<Char>(data::digits[index]);
-  return end;
+  out -= 2;
+  copy2(out, data::digits[value]);
+  return {out, end};
 }
 
-template <typename Int> constexpr int digits10() noexcept {
-  return std::numeric_limits<Int>::digits10;
-}
-template <> constexpr int digits10<int128_t>() noexcept { return 38; }
-template <> constexpr int digits10<uint128_t>() noexcept { return 38; }
-
-template <typename Char, typename UInt, typename Iterator, typename F>
-inline Iterator format_decimal(Iterator out, UInt value, int num_digits,
-                               F add_thousands_sep) {
-  FMT_ASSERT(num_digits >= 0, "invalid digit count");
-  // Buffer should be large enough to hold all digits (<= digits10 + 1).
-  enum { max_size = digits10<UInt>() + 1 };
-  Char buffer[2 * max_size];
-  auto end = format_decimal(buffer, value, num_digits, add_thousands_sep);
-  return internal::copy_str<Char>(buffer, end, out);
-}
-
-template <typename Char, typename It, typename UInt>
-inline It format_decimal(It out, UInt value, int num_digits) {
-  return format_decimal<Char>(out, value, num_digits, [](Char*) {});
+template <typename Char, typename UInt, typename Iterator,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<Iterator>>::value)>
+inline format_decimal_result<Iterator> format_decimal(Iterator out, UInt value,
+                                                      int size) {
+  // Buffer is large enough to hold all digits (digits10 + 1).
+  Char buffer[digits10<UInt>() + 1];
+  auto end = format_decimal(buffer, value, size).end;
+  return {out, detail::copy_str<Char>(buffer, end, out)};
 }
 
 template <unsigned BASE_BITS, typename Char, typename UInt>
@@ -955,7 +1093,7 @@
 }
 
 template <unsigned BASE_BITS, typename Char>
-Char* format_uint(Char* buffer, internal::fallback_uintptr n, int num_digits,
+Char* format_uint(Char* buffer, detail::fallback_uintptr n, int num_digits,
                   bool = false) {
   auto char_digits = std::numeric_limits<unsigned char>::digits / 4;
   int start = (num_digits + char_digits - 1) / char_digits - 1;
@@ -978,79 +1116,58 @@
 
 template <unsigned BASE_BITS, typename Char, typename It, typename UInt>
 inline It format_uint(It out, UInt value, int num_digits, bool upper = false) {
+  if (auto ptr = to_pointer<Char>(out, to_unsigned(num_digits))) {
+    format_uint<BASE_BITS>(ptr, value, num_digits, upper);
+    return out;
+  }
   // Buffer should be large enough to hold all digits (digits / BASE_BITS + 1).
   char buffer[num_bits<UInt>() / BASE_BITS + 1];
   format_uint<BASE_BITS>(buffer, value, num_digits, upper);
-  return internal::copy_str<Char>(buffer, buffer + num_digits, out);
+  return detail::copy_str<Char>(buffer, buffer + num_digits, out);
 }
 
-#ifndef _WIN32
-#  define FMT_USE_WINDOWS_H 0
-#elif !defined(FMT_USE_WINDOWS_H)
-#  define FMT_USE_WINDOWS_H 1
-#endif
-
-// Define FMT_USE_WINDOWS_H to 0 to disable use of windows.h.
-// All the functionality that relies on it will be disabled too.
-#if FMT_USE_WINDOWS_H
 // A converter from UTF-8 to UTF-16.
-// It is only provided for Windows since other systems support UTF-8 natively.
 class utf8_to_utf16 {
  private:
   wmemory_buffer buffer_;
 
  public:
   FMT_API explicit utf8_to_utf16(string_view s);
-  operator wstring_view() const { return wstring_view(&buffer_[0], size()); }
+  operator wstring_view() const { return {&buffer_[0], size()}; }
   size_t size() const { return buffer_.size() - 1; }
   const wchar_t* c_str() const { return &buffer_[0]; }
-  std::wstring str() const { return std::wstring(&buffer_[0], size()); }
+  std::wstring str() const { return {&buffer_[0], size()}; }
 };
 
-// A converter from UTF-16 to UTF-8.
-// It is only provided for Windows since other systems support UTF-8 natively.
-class utf16_to_utf8 {
- private:
-  memory_buffer buffer_;
-
- public:
-  utf16_to_utf8() {}
-  FMT_API explicit utf16_to_utf8(wstring_view s);
-  operator string_view() const { return string_view(&buffer_[0], size()); }
-  size_t size() const { return buffer_.size() - 1; }
-  const char* c_str() const { return &buffer_[0]; }
-  std::string str() const { return std::string(&buffer_[0], size()); }
-
-  // Performs conversion returning a system error code instead of
-  // throwing exception on conversion error. This method may still throw
-  // in case of memory allocation error.
-  FMT_API int convert(wstring_view s);
-};
-
-FMT_API void format_windows_error(internal::buffer<char>& out, int error_code,
-                                  string_view message) FMT_NOEXCEPT;
-#endif
-
 template <typename T = void> struct null {};
 
 // Workaround an array initialization issue in gcc 4.8.
 template <typename Char> struct fill_t {
  private:
-  Char data_[6];
+  enum { max_size = 4 };
+  Char data_[max_size] = {Char(' '), Char(0), Char(0), Char(0)};
+  unsigned char size_ = 1;
 
  public:
+  FMT_CONSTEXPR void operator=(basic_string_view<Char> s) {
+    auto size = s.size();
+    if (size > max_size) {
+      FMT_THROW(format_error("invalid fill"));
+      return;
+    }
+    for (size_t i = 0; i < size; ++i) data_[i] = s[i];
+    size_ = static_cast<unsigned char>(size);
+  }
+
+  size_t size() const { return size_; }
+  const Char* data() const { return data_; }
+
   FMT_CONSTEXPR Char& operator[](size_t index) { return data_[index]; }
   FMT_CONSTEXPR const Char& operator[](size_t index) const {
     return data_[index];
   }
-
-  static FMT_CONSTEXPR fill_t<Char> make() {
-    auto fill = fill_t<Char>();
-    fill[0] = Char(' ');
-    return fill;
-  }
 };
-}  // namespace internal
+}  // namespace detail
 
 // We cannot use enum classes as bit fields because of a gcc bug
 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414.
@@ -1072,7 +1189,7 @@
   align_t align : 4;
   sign_t sign : 3;
   bool alt : 1;  // Alternate form ('#').
-  internal::fill_t<Char> fill;
+  detail::fill_t<Char> fill;
 
   constexpr basic_format_specs()
       : width(0),
@@ -1080,13 +1197,84 @@
         type(0),
         align(align::none),
         sign(sign::none),
-        alt(false),
-        fill(internal::fill_t<Char>::make()) {}
+        alt(false) {}
 };
 
 using format_specs = basic_format_specs<char>;
 
-namespace internal {
+namespace detail {
+namespace dragonbox {
+
+// Type-specific information that Dragonbox uses.
+template <class T> struct float_info;
+
+template <> struct float_info<float> {
+  using carrier_uint = uint32_t;
+  static const int significand_bits = 23;
+  static const int exponent_bits = 8;
+  static const int min_exponent = -126;
+  static const int max_exponent = 127;
+  static const int exponent_bias = -127;
+  static const int decimal_digits = 9;
+  static const int kappa = 1;
+  static const int big_divisor = 100;
+  static const int small_divisor = 10;
+  static const int min_k = -31;
+  static const int max_k = 46;
+  static const int cache_bits = 64;
+  static const int divisibility_check_by_5_threshold = 39;
+  static const int case_fc_pm_half_lower_threshold = -1;
+  static const int case_fc_pm_half_upper_threshold = 6;
+  static const int case_fc_lower_threshold = -2;
+  static const int case_fc_upper_threshold = 6;
+  static const int case_shorter_interval_left_endpoint_lower_threshold = 2;
+  static const int case_shorter_interval_left_endpoint_upper_threshold = 3;
+  static const int shorter_interval_tie_lower_threshold = -35;
+  static const int shorter_interval_tie_upper_threshold = -35;
+  static const int max_trailing_zeros = 7;
+};
+
+template <> struct float_info<double> {
+  using carrier_uint = uint64_t;
+  static const int significand_bits = 52;
+  static const int exponent_bits = 11;
+  static const int min_exponent = -1022;
+  static const int max_exponent = 1023;
+  static const int exponent_bias = -1023;
+  static const int decimal_digits = 17;
+  static const int kappa = 2;
+  static const int big_divisor = 1000;
+  static const int small_divisor = 100;
+  static const int min_k = -292;
+  static const int max_k = 326;
+  static const int cache_bits = 128;
+  static const int divisibility_check_by_5_threshold = 86;
+  static const int case_fc_pm_half_lower_threshold = -2;
+  static const int case_fc_pm_half_upper_threshold = 9;
+  static const int case_fc_lower_threshold = -4;
+  static const int case_fc_upper_threshold = 9;
+  static const int case_shorter_interval_left_endpoint_lower_threshold = 2;
+  static const int case_shorter_interval_left_endpoint_upper_threshold = 3;
+  static const int shorter_interval_tie_lower_threshold = -77;
+  static const int shorter_interval_tie_upper_threshold = -77;
+  static const int max_trailing_zeros = 16;
+};
+
+template <typename T> struct decimal_fp {
+  using significand_type = typename float_info<T>::carrier_uint;
+  significand_type significand;
+  int exponent;
+};
+
+template <typename T> FMT_API decimal_fp<T> to_decimal(T x) FMT_NOEXCEPT;
+}  // namespace dragonbox
+
+template <typename T>
+constexpr typename dragonbox::float_info<T>::carrier_uint exponent_mask() {
+  using uint = typename dragonbox::float_info<T>::carrier_uint;
+  return ((uint(1) << dragonbox::float_info<T>::exponent_bits) - 1)
+         << dragonbox::float_info<T>::significand_bits;
+}
 
 // A floating-point presentation format.
 enum class float_format : unsigned char {
@@ -1102,10 +1290,9 @@
   sign_t sign : 8;
   bool upper : 1;
   bool locale : 1;
-  bool percent : 1;
   bool binary32 : 1;
   bool use_grisu : 1;
-  bool trailing_zeros : 1;
+  bool showpoint : 1;
 };
 
 // Writes the exponent exp in the form "[+-]d{2,3}" to buffer.
@@ -1118,123 +1305,17 @@
     *it++ = static_cast<Char>('+');
   }
   if (exp >= 100) {
-    const char* top = data::digits + (exp / 100) * 2;
+    const char* top = data::digits[exp / 100];
     if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
     *it++ = static_cast<Char>(top[1]);
     exp %= 100;
   }
-  const char* d = data::digits + exp * 2;
+  const char* d = data::digits[exp];
   *it++ = static_cast<Char>(d[0]);
   *it++ = static_cast<Char>(d[1]);
   return it;
 }
 
-template <typename Char> class float_writer {
- private:
-  // The number is given as v = digits_ * pow(10, exp_).
-  const char* digits_;
-  int num_digits_;
-  int exp_;
-  size_t size_;
-  float_specs specs_;
-  Char decimal_point_;
-
-  template <typename It> It prettify(It it) const {
-    // pow(10, full_exp - 1) <= v <= pow(10, full_exp).
-    int full_exp = num_digits_ + exp_;
-    if (specs_.format == float_format::exp) {
-      // Insert a decimal point after the first digit and add an exponent.
-      *it++ = static_cast<Char>(*digits_);
-      int num_zeros = specs_.precision - num_digits_;
-      bool trailing_zeros = num_zeros > 0 && specs_.trailing_zeros;
-      if (num_digits_ > 1 || trailing_zeros) *it++ = decimal_point_;
-      it = copy_str<Char>(digits_ + 1, digits_ + num_digits_, it);
-      if (trailing_zeros)
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-      *it++ = static_cast<Char>(specs_.upper ? 'E' : 'e');
-      return write_exponent<Char>(full_exp - 1, it);
-    }
-    if (num_digits_ <= full_exp) {
-      // 1234e7 -> 12340000000[.0+]
-      it = copy_str<Char>(digits_, digits_ + num_digits_, it);
-      it = std::fill_n(it, full_exp - num_digits_, static_cast<Char>('0'));
-      if (specs_.trailing_zeros) {
-        *it++ = decimal_point_;
-        int num_zeros = specs_.precision - full_exp;
-        if (num_zeros <= 0) {
-          if (specs_.format != float_format::fixed)
-            *it++ = static_cast<Char>('0');
-          return it;
-        }
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-        if (num_zeros > 1000)
-          throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
-#endif
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-      }
-    } else if (full_exp > 0) {
-      // 1234e-2 -> 12.34[0+]
-      it = copy_str<Char>(digits_, digits_ + full_exp, it);
-      if (!specs_.trailing_zeros) {
-        // Remove trailing zeros.
-        int num_digits = num_digits_;
-        while (num_digits > full_exp && digits_[num_digits - 1] == '0')
-          --num_digits;
-        if (num_digits != full_exp) *it++ = decimal_point_;
-        return copy_str<Char>(digits_ + full_exp, digits_ + num_digits, it);
-      }
-      *it++ = decimal_point_;
-      it = copy_str<Char>(digits_ + full_exp, digits_ + num_digits_, it);
-      if (specs_.precision > num_digits_) {
-        // Add trailing zeros.
-        int num_zeros = specs_.precision - num_digits_;
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-      }
-    } else {
-      // 1234e-6 -> 0.001234
-      *it++ = static_cast<Char>('0');
-      int num_zeros = -full_exp;
-      if (specs_.precision >= 0 && specs_.precision < num_zeros)
-        num_zeros = specs_.precision;
-      int num_digits = num_digits_;
-      if (!specs_.trailing_zeros)
-        while (num_digits > 0 && digits_[num_digits - 1] == '0') --num_digits;
-      if (num_zeros != 0 || num_digits != 0) {
-        *it++ = decimal_point_;
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-        it = copy_str<Char>(digits_, digits_ + num_digits, it);
-      }
-    }
-    return it;
-  }
-
- public:
-  float_writer(const char* digits, int num_digits, int exp, float_specs specs,
-               Char decimal_point)
-      : digits_(digits),
-        num_digits_(num_digits),
-        exp_(exp),
-        specs_(specs),
-        decimal_point_(decimal_point) {
-    int full_exp = num_digits + exp - 1;
-    int precision = specs.precision > 0 ? specs.precision : 16;
-    if (specs_.format == float_format::general &&
-        !(full_exp >= -4 && full_exp < precision)) {
-      specs_.format = float_format::exp;
-    }
-    size_ = prettify(counting_iterator()).count();
-    size_ += specs.sign ? 1 : 0;
-  }
-
-  size_t size() const { return size_; }
-  size_t width() const { return size(); }
-
-  template <typename It> void operator()(It&& it) {
-    if (specs_.sign) *it++ = static_cast<Char>(data::signs[specs_.sign]);
-    it = prettify(it);
-  }
-};
-
 template <typename T>
 int format_float(T value, int precision, float_specs specs, buffer<char>& buf);
 
@@ -1244,7 +1325,7 @@
                    buffer<char>& buf);
 
 template <typename T> T promote_float(T value) { return value; }
-inline double promote_float(float value) { return value; }
+inline double promote_float(float value) { return static_cast<double>(value); }
 
 template <typename Handler>
 FMT_CONSTEXPR void handle_int_type_spec(char spec, Handler&& handler) {
@@ -1264,9 +1345,15 @@
   case 'o':
     handler.on_oct();
     break;
+#ifdef FMT_DEPRECATED_N_SPECIFIER
   case 'n':
+#endif
+  case 'L':
     handler.on_num();
     break;
+  case 'c':
+    handler.on_chr();
+    break;
   default:
     handler.on_error();
   }
@@ -1276,11 +1363,11 @@
 FMT_CONSTEXPR float_specs parse_float_type_spec(
     const basic_format_specs<Char>& specs, ErrorHandler&& eh = {}) {
   auto result = float_specs();
-  result.trailing_zeros = specs.alt;
+  result.showpoint = specs.alt;
   switch (specs.type) {
   case 0:
     result.format = float_format::general;
-    result.trailing_zeros |= specs.precision != 0;
+    result.showpoint |= specs.precision > 0;
     break;
   case 'G':
     result.upper = true;
@@ -1293,28 +1380,25 @@
     FMT_FALLTHROUGH;
   case 'e':
     result.format = float_format::exp;
-    result.trailing_zeros |= specs.precision != 0;
+    result.showpoint |= specs.precision != 0;
     break;
   case 'F':
     result.upper = true;
     FMT_FALLTHROUGH;
   case 'f':
     result.format = float_format::fixed;
-    result.trailing_zeros |= specs.precision != 0;
+    result.showpoint |= specs.precision != 0;
     break;
-#if FMT_DEPRECATED_PERCENT
-  case '%':
-    result.format = float_format::fixed;
-    result.percent = true;
-    break;
-#endif
   case 'A':
     result.upper = true;
     FMT_FALLTHROUGH;
   case 'a':
     result.format = float_format::hex;
     break;
+#ifdef FMT_DEPRECATED_N_SPECIFIER
   case 'n':
+#endif
+  case 'L':
     result.locale = true;
     break;
   default:
@@ -1363,6 +1447,7 @@
   FMT_CONSTEXPR void on_bin() {}
   FMT_CONSTEXPR void on_oct() {}
   FMT_CONSTEXPR void on_num() {}
+  FMT_CONSTEXPR void on_chr() {}
 
   FMT_CONSTEXPR void on_error() {
     ErrorHandler::on_error("invalid type specifier");
@@ -1394,386 +1479,669 @@
   FMT_CONSTEXPR void on_pointer() {}
 };
 
-template <typename Context>
-void arg_map<Context>::init(const basic_format_args<Context>& args) {
-  if (map_) return;
-  map_ = new entry[internal::to_unsigned(args.max_size())];
-  if (args.is_packed()) {
-    for (int i = 0;; ++i) {
-      internal::type arg_type = args.type(i);
-      if (arg_type == internal::none_type) return;
-      if (arg_type == internal::named_arg_type) push_back(args.values_[i]);
-    }
-  }
-  for (int i = 0, n = args.max_size(); i < n; ++i) {
-    auto type = args.args_[i].type_;
-    if (type == internal::named_arg_type) push_back(args.args_[i].value_);
-  }
+template <typename OutputIt, typename Char>
+FMT_NOINLINE OutputIt fill(OutputIt it, size_t n, const fill_t<Char>& fill) {
+  auto fill_size = fill.size();
+  if (fill_size == 1) return std::fill_n(it, n, fill[0]);
+  for (size_t i = 0; i < n; ++i) it = std::copy_n(fill.data(), fill_size, it);
+  return it;
 }
 
-template <typename Char> struct nonfinite_writer {
-  sign_t sign;
-  const char* str;
-  static constexpr size_t str_size = 3;
+// Writes the output of f, padded according to format specifications in specs.
+// size: output size in code units.
+// width: output display width in (terminal) column positions.
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+inline OutputIt write_padded(OutputIt out,
+                             const basic_format_specs<Char>& specs, size_t size,
+                             size_t width, F&& f) {
+  static_assert(align == align::left || align == align::right, "");
+  unsigned spec_width = to_unsigned(specs.width);
+  size_t padding = spec_width > width ? spec_width - width : 0;
+  auto* shifts = align == align::left ? data::left_padding_shifts
+                                      : data::right_padding_shifts;
+  size_t left_padding = padding >> shifts[specs.align];
+  auto it = reserve(out, size + padding * specs.fill.size());
+  it = fill(it, left_padding, specs.fill);
+  it = f(it);
+  it = fill(it, padding - left_padding, specs.fill);
+  return base_iterator(out, it);
+}
 
-  size_t size() const { return str_size + (sign ? 1 : 0); }
-  size_t width() const { return size(); }
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+inline OutputIt write_padded(OutputIt out,
+                             const basic_format_specs<Char>& specs, size_t size,
+                             F&& f) {
+  return write_padded<align>(out, specs, size, size, f);
+}
 
-  template <typename It> void operator()(It&& it) const {
-    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
-    it = copy_str<Char>(str, str + str_size, it);
-  }
-};
+template <typename Char, typename OutputIt>
+OutputIt write_bytes(OutputIt out, string_view bytes,
+                     const basic_format_specs<Char>& specs) {
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, bytes.size(), [bytes](iterator it) {
+    const char* data = bytes.data();
+    return copy_str<Char>(data, data + bytes.size(), it);
+  });
+}
 
-// This template provides operations for formatting and writing data into a
-// character range.
-template <typename Range> class basic_writer {
- public:
-  using char_type = typename Range::value_type;
-  using iterator = typename Range::iterator;
-  using format_specs = basic_format_specs<char_type>;
+// Data for write_int that doesn't depend on output iterator type. It is used to
+// avoid template code bloat.
+template <typename Char> struct write_int_data {
+  size_t size;
+  size_t padding;
 
- private:
-  iterator out_;  // Output iterator.
-  locale_ref locale_;
-
-  // Attempts to reserve space for n extra characters in the output range.
-  // Returns a pointer to the reserved range or a reference to out_.
-  auto reserve(std::size_t n) -> decltype(internal::reserve(out_, n)) {
-    return internal::reserve(out_, n);
-  }
-
-  template <typename F> struct padded_int_writer {
-    size_t size_;
-    string_view prefix;
-    char_type fill;
-    std::size_t padding;
-    F f;
-
-    size_t size() const { return size_; }
-    size_t width() const { return size_; }
-
-    template <typename It> void operator()(It&& it) const {
-      if (prefix.size() != 0)
-        it = copy_str<char_type>(prefix.begin(), prefix.end(), it);
-      it = std::fill_n(it, padding, fill);
-      f(it);
-    }
-  };
-
-  // Writes an integer in the format
-  //   <left-padding><prefix><numeric-padding><digits><right-padding>
-  // where <digits> are written by f(it).
-  template <typename F>
-  void write_int(int num_digits, string_view prefix, format_specs specs, F f) {
-    std::size_t size = prefix.size() + to_unsigned(num_digits);
-    char_type fill = specs.fill[0];
-    std::size_t padding = 0;
+  write_int_data(int num_digits, string_view prefix,
+                 const basic_format_specs<Char>& specs)
+      : size(prefix.size() + to_unsigned(num_digits)), padding(0) {
     if (specs.align == align::numeric) {
-      auto unsiged_width = to_unsigned(specs.width);
-      if (unsiged_width > size) {
-        padding = unsiged_width - size;
-        size = unsiged_width;
+      auto width = to_unsigned(specs.width);
+      if (width > size) {
+        padding = width - size;
+        size = width;
       }
     } else if (specs.precision > num_digits) {
       size = prefix.size() + to_unsigned(specs.precision);
       padding = to_unsigned(specs.precision - num_digits);
-      fill = static_cast<char_type>('0');
     }
-    if (specs.align == align::none) specs.align = align::right;
-    write_padded(specs, padded_int_writer<F>{size, prefix, fill, padding, f});
+  }
+};
+
+// Writes an integer in the format
+//   <left-padding><prefix><numeric-padding><digits><right-padding>
+// where <digits> are written by f(it).
+template <typename OutputIt, typename Char, typename F>
+OutputIt write_int(OutputIt out, int num_digits, string_view prefix,
+                   const basic_format_specs<Char>& specs, F f) {
+  auto data = write_int_data<Char>(num_digits, prefix, specs);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded<align::right>(out, specs, data.size, [=](iterator it) {
+    if (prefix.size() != 0)
+      it = copy_str<Char>(prefix.begin(), prefix.end(), it);
+    it = std::fill_n(it, data.padding, static_cast<Char>('0'));
+    return f(it);
+  });
+}
+
+template <typename StrChar, typename Char, typename OutputIt>
+OutputIt write(OutputIt out, basic_string_view<StrChar> s,
+               const basic_format_specs<Char>& specs) {
+  auto data = s.data();
+  auto size = s.size();
+  if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
+    size = code_point_index(s, to_unsigned(specs.precision));
+  auto width = specs.width != 0
+                   ? count_code_points(basic_string_view<StrChar>(data, size))
+                   : 0;
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, size, width, [=](iterator it) {
+    return copy_str<Char>(data, data + size, it);
+  });
+}
+
+// The handle_int_type_spec handler that writes an integer.
+template <typename OutputIt, typename Char, typename UInt> struct int_writer {
+  OutputIt out;
+  locale_ref locale;
+  const basic_format_specs<Char>& specs;
+  UInt abs_value;
+  char prefix[4];
+  unsigned prefix_size;
+
+  using iterator =
+      remove_reference_t<decltype(reserve(std::declval<OutputIt&>(), 0))>;
+
+  string_view get_prefix() const { return string_view(prefix, prefix_size); }
+
+  template <typename Int>
+  int_writer(OutputIt output, locale_ref loc, Int value,
+             const basic_format_specs<Char>& s)
+      : out(output),
+        locale(loc),
+        specs(s),
+        abs_value(static_cast<UInt>(value)),
+        prefix_size(0) {
+    static_assert(std::is_same<uint32_or_64_or_128_t<Int>, UInt>::value, "");
+    if (is_negative(value)) {
+      prefix[0] = '-';
+      ++prefix_size;
+      abs_value = 0 - abs_value;
+    } else if (specs.sign != sign::none && specs.sign != sign::minus) {
+      prefix[0] = specs.sign == sign::plus ? '+' : ' ';
+      ++prefix_size;
+    }
   }
 
-  // Writes a decimal integer.
-  template <typename Int> void write_decimal(Int value) {
-    auto abs_value = static_cast<uint32_or_64_or_128_t<Int>>(value);
-    bool negative = is_negative(value);
-    // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
-    if (negative) abs_value = ~abs_value + 1;
+  void on_dec() {
+    auto num_digits = count_digits(abs_value);
+    out = write_int(
+        out, num_digits, get_prefix(), specs, [this, num_digits](iterator it) {
+          return format_decimal<Char>(it, abs_value, num_digits).end;
+        });
+  }
+
+  void on_hex() {
+    if (specs.alt) {
+      prefix[prefix_size++] = '0';
+      prefix[prefix_size++] = specs.type;
+    }
+    int num_digits = count_digits<4>(abs_value);
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<4, Char>(it, abs_value, num_digits,
+                                                  specs.type != 'x');
+                    });
+  }
+
+  void on_bin() {
+    if (specs.alt) {
+      prefix[prefix_size++] = '0';
+      prefix[prefix_size++] = static_cast<char>(specs.type);
+    }
+    int num_digits = count_digits<1>(abs_value);
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<1, Char>(it, abs_value, num_digits);
+                    });
+  }
+
+  void on_oct() {
+    int num_digits = count_digits<3>(abs_value);
+    if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
+      // Octal prefix '0' is counted as a digit, so only add it if precision
+      // is not greater than the number of digits.
+      prefix[prefix_size++] = '0';
+    }
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<3, Char>(it, abs_value, num_digits);
+                    });
+  }
+
+  enum { sep_size = 1 };
+
+  void on_num() {
+    std::string groups = grouping<Char>(locale);
+    if (groups.empty()) return on_dec();
+    auto sep = thousands_sep<Char>(locale);
+    if (!sep) return on_dec();
     int num_digits = count_digits(abs_value);
-    auto&& it = reserve((negative ? 1 : 0) + static_cast<size_t>(num_digits));
-    if (negative) *it++ = static_cast<char_type>('-');
-    it = format_decimal<char_type>(it, abs_value, num_digits);
-  }
-
-  // The handle_int_type_spec handler that writes an integer.
-  template <typename Int, typename Specs> struct int_writer {
-    using unsigned_type = uint32_or_64_or_128_t<Int>;
-
-    basic_writer<Range>& writer;
-    const Specs& specs;
-    unsigned_type abs_value;
-    char prefix[4];
-    unsigned prefix_size;
-
-    string_view get_prefix() const { return string_view(prefix, prefix_size); }
-
-    int_writer(basic_writer<Range>& w, Int value, const Specs& s)
-        : writer(w),
-          specs(s),
-          abs_value(static_cast<unsigned_type>(value)),
-          prefix_size(0) {
-      if (is_negative(value)) {
-        prefix[0] = '-';
-        ++prefix_size;
-        abs_value = 0 - abs_value;
-      } else if (specs.sign != sign::none && specs.sign != sign::minus) {
-        prefix[0] = specs.sign == sign::plus ? '+' : ' ';
-        ++prefix_size;
-      }
+    int size = num_digits, n = num_digits;
+    std::string::const_iterator group = groups.cbegin();
+    while (group != groups.cend() && n > *group && *group > 0 &&
+           *group != max_value<char>()) {
+      size += sep_size;
+      n -= *group;
+      ++group;
     }
-
-    struct dec_writer {
-      unsigned_type abs_value;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = internal::format_decimal<char_type>(it, abs_value, num_digits);
-      }
-    };
-
-    void on_dec() {
-      int num_digits = count_digits(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       dec_writer{abs_value, num_digits});
-    }
-
-    struct hex_writer {
-      int_writer& self;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = format_uint<4, char_type>(it, self.abs_value, num_digits,
-                                       self.specs.type != 'x');
-      }
-    };
-
-    void on_hex() {
-      if (specs.alt) {
-        prefix[prefix_size++] = '0';
-        prefix[prefix_size++] = specs.type;
-      }
-      int num_digits = count_digits<4>(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       hex_writer{*this, num_digits});
-    }
-
-    template <int BITS> struct bin_writer {
-      unsigned_type abs_value;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = format_uint<BITS, char_type>(it, abs_value, num_digits);
-      }
-    };
-
-    void on_bin() {
-      if (specs.alt) {
-        prefix[prefix_size++] = '0';
-        prefix[prefix_size++] = static_cast<char>(specs.type);
-      }
-      int num_digits = count_digits<1>(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       bin_writer<1>{abs_value, num_digits});
-    }
-
-    void on_oct() {
-      int num_digits = count_digits<3>(abs_value);
-      if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
-        // Octal prefix '0' is counted as a digit, so only add it if precision
-        // is not greater than the number of digits.
-        prefix[prefix_size++] = '0';
-      }
-      writer.write_int(num_digits, get_prefix(), specs,
-                       bin_writer<3>{abs_value, num_digits});
-    }
-
-    enum { sep_size = 1 };
-
-    struct num_writer {
-      unsigned_type abs_value;
-      int size;
-      const std::string& groups;
-      char_type sep;
-
-      template <typename It> void operator()(It&& it) const {
-        basic_string_view<char_type> s(&sep, sep_size);
-        // Index of a decimal digit with the least significant digit having
-        // index 0.
-        int digit_index = 0;
-        std::string::const_iterator group = groups.cbegin();
-        it = format_decimal<char_type>(
-            it, abs_value, size,
-            [this, s, &group, &digit_index](char_type*& buffer) {
-              if (*group <= 0 || ++digit_index % *group != 0 ||
-                  *group == max_value<char>())
-                return;
-              if (group + 1 != groups.cend()) {
-                digit_index = 0;
-                ++group;
-              }
-              buffer -= s.size();
-              std::uninitialized_copy(s.data(), s.data() + s.size(),
-                                      make_checked(buffer, s.size()));
-            });
-      }
-    };
-
-    void on_num() {
-      std::string groups = grouping<char_type>(writer.locale_);
-      if (groups.empty()) return on_dec();
-      auto sep = thousands_sep<char_type>(writer.locale_);
-      if (!sep) return on_dec();
-      int num_digits = count_digits(abs_value);
-      int size = num_digits;
-      std::string::const_iterator group = groups.cbegin();
-      while (group != groups.cend() && num_digits > *group && *group > 0 &&
-             *group != max_value<char>()) {
-        size += sep_size;
-        num_digits -= *group;
+    if (group == groups.cend()) size += sep_size * ((n - 1) / groups.back());
+    char digits[40];
+    format_decimal(digits, abs_value, num_digits);
+    basic_memory_buffer<Char> buffer;
+    size += static_cast<int>(prefix_size);
+    const auto usize = to_unsigned(size);
+    buffer.resize(usize);
+    basic_string_view<Char> s(&sep, sep_size);
+    // Index of a decimal digit with the least significant digit having index 0.
+    int digit_index = 0;
+    group = groups.cbegin();
+    auto p = buffer.data() + size - 1;
+    for (int i = num_digits - 1; i > 0; --i) {
+      *p-- = static_cast<Char>(digits[i]);
+      if (*group <= 0 || ++digit_index % *group != 0 ||
+          *group == max_value<char>())
+        continue;
+      if (group + 1 != groups.cend()) {
+        digit_index = 0;
         ++group;
       }
-      if (group == groups.cend())
-        size += sep_size * ((num_digits - 1) / groups.back());
-      writer.write_int(size, get_prefix(), specs,
-                       num_writer{abs_value, size, groups, sep});
+      std::uninitialized_copy(s.data(), s.data() + s.size(),
+                              make_checked(p, s.size()));
+      p -= s.size();
     }
-
-    FMT_NORETURN void on_error() {
-      FMT_THROW(format_error("invalid type specifier"));
-    }
-  };
-
-  template <typename Char> struct str_writer {
-    const Char* s;
-    size_t size_;
-
-    size_t size() const { return size_; }
-    size_t width() const {
-      return count_code_points(basic_string_view<Char>(s, size_));
-    }
-
-    template <typename It> void operator()(It&& it) const {
-      it = copy_str<char_type>(s, s + size_, it);
-    }
-  };
-
-  template <typename UIntPtr> struct pointer_writer {
-    UIntPtr value;
-    int num_digits;
-
-    size_t size() const { return to_unsigned(num_digits) + 2; }
-    size_t width() const { return size(); }
-
-    template <typename It> void operator()(It&& it) const {
-      *it++ = static_cast<char_type>('0');
-      *it++ = static_cast<char_type>('x');
-      it = format_uint<4, char_type>(it, value, num_digits);
-    }
-  };
-
- public:
-  explicit basic_writer(Range out, locale_ref loc = locale_ref())
-      : out_(out.begin()), locale_(loc) {}
-
-  iterator out() const { return out_; }
-
-  // Writes a value in the format
-  //   <left-padding><value><right-padding>
-  // where <value> is written by f(it).
-  template <typename F> void write_padded(const format_specs& specs, F&& f) {
-    // User-perceived width (in code points).
-    unsigned width = to_unsigned(specs.width);
-    size_t size = f.size();  // The number of code units.
-    size_t num_code_points = width != 0 ? f.width() : size;
-    if (width <= num_code_points) return f(reserve(size));
-    auto&& it = reserve(width + (size - num_code_points));
-    char_type fill = specs.fill[0];
-    std::size_t padding = width - num_code_points;
-    if (specs.align == align::right) {
-      it = std::fill_n(it, padding, fill);
-      f(it);
-    } else if (specs.align == align::center) {
-      std::size_t left_padding = padding / 2;
-      it = std::fill_n(it, left_padding, fill);
-      f(it);
-      it = std::fill_n(it, padding - left_padding, fill);
-    } else {
-      f(it);
-      it = std::fill_n(it, padding, fill);
-    }
+    *p-- = static_cast<Char>(*digits);
+    if (prefix_size != 0) *p = static_cast<Char>('-');
+    auto data = buffer.data();
+    out = write_padded<align::right>(
+        out, specs, usize, usize,
+        [=](iterator it) { return copy_str<Char>(data, data + size, it); });
   }
 
-  void write(int value) { write_decimal(value); }
-  void write(long value) { write_decimal(value); }
-  void write(long long value) { write_decimal(value); }
+  void on_chr() { *out++ = static_cast<Char>(abs_value); }
 
-  void write(unsigned value) { write_decimal(value); }
-  void write(unsigned long value) { write_decimal(value); }
-  void write(unsigned long long value) { write_decimal(value); }
+  FMT_NORETURN void on_error() {
+    FMT_THROW(format_error("invalid type specifier"));
+  }
+};
 
-#if FMT_USE_INT128
-  void write(int128_t value) { write_decimal(value); }
-  void write(uint128_t value) { write_decimal(value); }
+template <typename Char, typename OutputIt>
+OutputIt write_nonfinite(OutputIt out, bool isinf,
+                         const basic_format_specs<Char>& specs,
+                         const float_specs& fspecs) {
+  auto str =
+      isinf ? (fspecs.upper ? "INF" : "inf") : (fspecs.upper ? "NAN" : "nan");
+  constexpr size_t str_size = 3;
+  auto sign = fspecs.sign;
+  auto size = str_size + (sign ? 1 : 0);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, size, [=](iterator it) {
+    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+    return copy_str<Char>(str, str + str_size, it);
+  });
+}
+
+// A decimal floating-point number significand * pow(10, exp).
+struct big_decimal_fp {
+  const char* significand;
+  int significand_size;
+  int exponent;
+};
+
+inline int get_significand_size(const big_decimal_fp& fp) {
+  return fp.significand_size;
+}
+template <typename T>
+inline int get_significand_size(const dragonbox::decimal_fp<T>& fp) {
+  return count_digits(fp.significand);
+}
+
+template <typename Char, typename OutputIt>
+inline OutputIt write_significand(OutputIt out, const char* significand,
+                                  int& significand_size) {
+  return copy_str<Char>(significand, significand + significand_size, out);
+}
+template <typename Char, typename OutputIt, typename UInt>
+inline OutputIt write_significand(OutputIt out, UInt significand,
+                                  int significand_size) {
+  return format_decimal<Char>(out, significand, significand_size).end;
+}
+
+template <typename Char, typename UInt,
+          FMT_ENABLE_IF(std::is_integral<UInt>::value)>
+inline Char* write_significand(Char* out, UInt significand,
+                               int significand_size, int integral_size,
+                               Char decimal_point) {
+  if (!decimal_point)
+    return format_decimal(out, significand, significand_size).end;
+  auto end = format_decimal(out + 1, significand, significand_size).end;
+  if (integral_size == 1)
+    out[0] = out[1];
+  else
+    std::copy_n(out + 1, integral_size, out);
+  out[integral_size] = decimal_point;
+  return end;
+}
+
+template <typename OutputIt, typename UInt, typename Char,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<OutputIt>>::value)>
+inline OutputIt write_significand(OutputIt out, UInt significand,
+                                  int significand_size, int integral_size,
+                                  Char decimal_point) {
+  // Buffer is large enough to hold digits (digits10 + 1) and a decimal point.
+  Char buffer[digits10<UInt>() + 2];
+  auto end = write_significand(buffer, significand, significand_size,
+                               integral_size, decimal_point);
+  return detail::copy_str<Char>(buffer, end, out);
+}
+
+template <typename OutputIt, typename Char>
+inline OutputIt write_significand(OutputIt out, const char* significand,
+                                  int significand_size, int integral_size,
+                                  Char decimal_point) {
+  out = detail::copy_str<Char>(significand, significand + integral_size, out);
+  if (!decimal_point) return out;
+  *out++ = decimal_point;
+  return detail::copy_str<Char>(significand + integral_size,
+                                significand + significand_size, out);
+}
+
+template <typename OutputIt, typename DecimalFP, typename Char>
+OutputIt write_float(OutputIt out, const DecimalFP& fp,
+                     const basic_format_specs<Char>& specs, float_specs fspecs,
+                     Char decimal_point) {
+  auto significand = fp.significand;
+  int significand_size = get_significand_size(fp);
+  static const Char zero = static_cast<Char>('0');
+  auto sign = fspecs.sign;
+  size_t size = to_unsigned(significand_size) + (sign ? 1 : 0);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+
+  int output_exp = fp.exponent + significand_size - 1;
+  auto use_exp_format = [=]() {
+    if (fspecs.format == float_format::exp) return true;
+    if (fspecs.format != float_format::general) return false;
+    // Use the fixed notation if the exponent is in [exp_lower, exp_upper),
+    // e.g. 0.0001 instead of 1e-04. Otherwise use the exponent notation.
+    const int exp_lower = -4, exp_upper = 16;
+    return output_exp < exp_lower ||
+           output_exp >= (fspecs.precision > 0 ? fspecs.precision : exp_upper);
+  };
+  if (use_exp_format()) {
+    int num_zeros = 0;
+    if (fspecs.showpoint) {
+      num_zeros = (std::max)(fspecs.precision - significand_size, 0);
+      size += to_unsigned(num_zeros);
+    } else if (significand_size == 1) {
+      decimal_point = Char();
+    }
+    auto abs_output_exp = output_exp >= 0 ? output_exp : -output_exp;
+    int exp_digits = 2;
+    if (abs_output_exp >= 100) exp_digits = abs_output_exp >= 1000 ? 4 : 3;
+
+    size += to_unsigned((decimal_point ? 1 : 0) + 2 + exp_digits);
+    char exp_char = fspecs.upper ? 'E' : 'e';
+    auto write = [=](iterator it) {
+      if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+      // Insert a decimal point after the first digit and add an exponent.
+      it = write_significand(it, significand, significand_size, 1,
+                             decimal_point);
+      if (num_zeros > 0) it = std::fill_n(it, num_zeros, zero);
+      *it++ = static_cast<Char>(exp_char);
+      return write_exponent<Char>(output_exp, it);
+    };
+    return specs.width > 0 ? write_padded<align::right>(out, specs, size, write)
+                           : base_iterator(out, write(reserve(out, size)));
+  }
+
+  int exp = fp.exponent + significand_size;
+  if (fp.exponent >= 0) {
+    // 1234e5 -> 123400000[.0+]
+    size += to_unsigned(fp.exponent);
+    int num_zeros = fspecs.precision - exp;
+#ifdef FMT_FUZZ
+    if (num_zeros > 5000)
+      throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
 #endif
+    if (fspecs.showpoint) {
+      if (num_zeros <= 0 && fspecs.format != float_format::fixed) num_zeros = 1;
+      if (num_zeros > 0) size += to_unsigned(num_zeros);
+    }
+    return write_padded<align::right>(out, specs, size, [&](iterator it) {
+      if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+      it = write_significand<Char>(it, significand, significand_size);
+      it = std::fill_n(it, fp.exponent, zero);
+      if (!fspecs.showpoint) return it;
+      *it++ = decimal_point;
+      return num_zeros > 0 ? std::fill_n(it, num_zeros, zero) : it;
+    });
+  } else if (exp > 0) {
+    // 1234e-2 -> 12.34[0+]
+    int num_zeros = fspecs.showpoint ? fspecs.precision - significand_size : 0;
+    size += 1 + to_unsigned(num_zeros > 0 ? num_zeros : 0);
+    return write_padded<align::right>(out, specs, size, [&](iterator it) {
+      if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+      it = write_significand(it, significand, significand_size, exp,
+                             decimal_point);
+      return num_zeros > 0 ? std::fill_n(it, num_zeros, zero) : it;
+    });
+  }
+  // 1234e-6 -> 0.001234
+  int num_zeros = -exp;
+  if (significand_size == 0 && fspecs.precision >= 0 &&
+      fspecs.precision < num_zeros) {
+    num_zeros = fspecs.precision;
+  }
+  size += 2 + to_unsigned(num_zeros);
+  return write_padded<align::right>(out, specs, size, [&](iterator it) {
+    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+    *it++ = zero;
+    if (num_zeros == 0 && significand_size == 0 && !fspecs.showpoint) return it;
+    *it++ = decimal_point;
+    it = std::fill_n(it, num_zeros, zero);
+    return write_significand<Char>(it, significand, significand_size);
+  });
+}
 
-  template <typename T, typename Spec>
-  void write_int(T value, const Spec& spec) {
-    handle_int_type_spec(spec.type, int_writer<T, Spec>(*this, value, spec));
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+OutputIt write(OutputIt out, T value, basic_format_specs<Char> specs,
+               locale_ref loc = {}) {
+  if (const_check(!is_supported_floating_point(value))) return out;
+  float_specs fspecs = parse_float_type_spec(specs);
+  fspecs.sign = specs.sign;
+  if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
+    fspecs.sign = sign::minus;
+    value = -value;
+  } else if (fspecs.sign == sign::minus) {
+    fspecs.sign = sign::none;
   }
 
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  void write(T value, format_specs specs = {}) {
-    float_specs fspecs = parse_float_type_spec(specs);
-    fspecs.sign = specs.sign;
-    if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
-      fspecs.sign = sign::minus;
-      value = -value;
-    } else if (fspecs.sign == sign::minus) {
-      fspecs.sign = sign::none;
-    }
+  if (!std::isfinite(value))
+    return write_nonfinite(out, std::isinf(value), specs, fspecs);
 
-    if (!std::isfinite(value)) {
-      auto str = std::isinf(value) ? (fspecs.upper ? "INF" : "inf")
-                                   : (fspecs.upper ? "NAN" : "nan");
-      return write_padded(specs, nonfinite_writer<char_type>{fspecs.sign, str});
-    }
+  if (specs.align == align::numeric && fspecs.sign) {
+    auto it = reserve(out, 1);
+    *it++ = static_cast<Char>(data::signs[fspecs.sign]);
+    out = base_iterator(out, it);
+    fspecs.sign = sign::none;
+    if (specs.width != 0) --specs.width;
+  }
 
-    if (specs.align == align::none) {
-      specs.align = align::right;
-    } else if (specs.align == align::numeric) {
-      if (fspecs.sign) {
-        auto&& it = reserve(1);
-        *it++ = static_cast<char_type>(data::signs[fspecs.sign]);
-        fspecs.sign = sign::none;
-        if (specs.width != 0) --specs.width;
-      }
-      specs.align = align::right;
-    }
+  memory_buffer buffer;
+  if (fspecs.format == float_format::hex) {
+    if (fspecs.sign) buffer.push_back(data::signs[fspecs.sign]);
+    snprintf_float(promote_float(value), specs.precision, fspecs, buffer);
+    return write_bytes(out, {buffer.data(), buffer.size()}, specs);
+  }
+  int precision = specs.precision >= 0 || !specs.type ? specs.precision : 6;
+  if (fspecs.format == float_format::exp) {
+    if (precision == max_value<int>())
+      FMT_THROW(format_error("number is too big"));
+    else
+      ++precision;
+  }
+  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
+  fspecs.use_grisu = is_fast_float<T>();
+  int exp = format_float(promote_float(value), precision, fspecs, buffer);
+  fspecs.precision = precision;
+  Char point =
+      fspecs.locale ? decimal_point<Char>(loc) : static_cast<Char>('.');
+  auto fp = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp};
+  return write_float(out, fp, specs, fspecs, point);
+}
 
-    memory_buffer buffer;
-    if (fspecs.format == float_format::hex) {
-      if (fspecs.sign) buffer.push_back(data::signs[fspecs.sign]);
-      snprintf_float(promote_float(value), specs.precision, fspecs, buffer);
-      write_padded(specs, str_writer<char>{buffer.data(), buffer.size()});
-      return;
-    }
-    int precision = specs.precision >= 0 || !specs.type ? specs.precision : 6;
-    if (fspecs.format == float_format::exp) ++precision;
-    if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
-    fspecs.use_grisu = use_grisu<T>();
-    if (const_check(FMT_DEPRECATED_PERCENT) && fspecs.percent) value *= 100;
-    int exp = format_float(promote_float(value), precision, fspecs, buffer);
-    if (const_check(FMT_DEPRECATED_PERCENT) && fspecs.percent) {
-      buffer.push_back('%');
-      --exp;  // Adjust decimal place position.
-    }
-    fspecs.precision = precision;
-    char_type point = fspecs.locale ? decimal_point<char_type>(locale_)
-                                    : static_cast<char_type>('.');
-    write_padded(specs, float_writer<char_type>(buffer.data(),
-                                                static_cast<int>(buffer.size()),
-                                                exp, fspecs, point));
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_fast_float<T>::value)>
+OutputIt write(OutputIt out, T value) {
+  if (const_check(!is_supported_floating_point(value))) return out;
+
+  using floaty = conditional_t<std::is_same<T, long double>::value, double, T>;
+  using uint = typename dragonbox::float_info<floaty>::carrier_uint;
+  auto bits = bit_cast<uint>(value);
+
+  auto fspecs = float_specs();
+  auto sign_bit = bits & (uint(1) << (num_bits<uint>() - 1));
+  if (sign_bit != 0) {
+    fspecs.sign = sign::minus;
+    value = -value;
+  }
+
+  static const auto specs = basic_format_specs<Char>();
+  uint mask = exponent_mask<floaty>();
+  if ((bits & mask) == mask)
+    return write_nonfinite(out, std::isinf(value), specs, fspecs);
+
+  auto dec = dragonbox::to_decimal(static_cast<floaty>(value));
+  return write_float(out, dec, specs, fspecs, static_cast<Char>('.'));
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_floating_point<T>::value &&
+                        !is_fast_float<T>::value)>
+inline OutputIt write(OutputIt out, T value) {
+  return write(out, value, basic_format_specs<Char>());
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write_char(OutputIt out, Char value,
+                    const basic_format_specs<Char>& specs) {
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, 1, [=](iterator it) {
+    *it++ = value;
+    return it;
+  });
+}
+
+template <typename Char, typename OutputIt, typename UIntPtr>
+OutputIt write_ptr(OutputIt out, UIntPtr value,
+                   const basic_format_specs<Char>* specs) {
+  int num_digits = count_digits<4>(value);
+  auto size = to_unsigned(num_digits) + size_t(2);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  auto write = [=](iterator it) {
+    *it++ = static_cast<Char>('0');
+    *it++ = static_cast<Char>('x');
+    return format_uint<4, Char>(it, value, num_digits);
+  };
+  return specs ? write_padded<align::right>(out, *specs, size, write)
+               : base_iterator(out, write(reserve(out, size)));
+}
+
+template <typename T> struct is_integral : std::is_integral<T> {};
+template <> struct is_integral<int128_t> : std::true_type {};
+template <> struct is_integral<uint128_t> : std::true_type {};
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, monostate) {
+  FMT_ASSERT(false, "");
+  return out;
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+OutputIt write(OutputIt out, string_view value) {
+  auto it = reserve(out, value.size());
+  it = copy_str<Char>(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, basic_string_view<Char> value) {
+  auto it = reserve(out, value.size());
+  it = std::copy(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
+
+template <typename Char>
+buffer_appender<Char> write(buffer_appender<Char> out,
+                            basic_string_view<Char> value) {
+  get_container(out).append(value.begin(), value.end());
+  return out;
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        !std::is_same<T, Char>::value)>
+OutputIt write(OutputIt out, T value) {
+  auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
+  bool negative = is_negative(value);
+  // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
+  if (negative) abs_value = ~abs_value + 1;
+  int num_digits = count_digits(abs_value);
+  auto size = (negative ? 1 : 0) + static_cast<size_t>(num_digits);
+  auto it = reserve(out, size);
+  if (auto ptr = to_pointer<Char>(it, size)) {
+    if (negative) *ptr++ = static_cast<Char>('-');
+    format_decimal<Char>(ptr, abs_value, num_digits);
+    return out;
+  }
+  if (negative) *it++ = static_cast<Char>('-');
+  it = format_decimal<Char>(it, abs_value, num_digits).end;
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, bool value) {
+  return write<Char>(out, string_view(value ? "true" : "false"));
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, Char value) {
+  auto it = reserve(out, 1);
+  *it++ = value;
+  return base_iterator(out, it);
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, const Char* value) {
+  if (!value) {
+    FMT_THROW(format_error("string pointer is null"));
+  } else {
+    auto length = std::char_traits<Char>::length(value);
+    out = write(out, basic_string_view<Char>(value, length));
+  }
+  return out;
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, const void* value) {
+  return write_ptr<Char>(out, to_uintptr(value), nullptr);
+}
+
+template <typename Char, typename OutputIt, typename T>
+auto write(OutputIt out, const T& value) -> typename std::enable_if<
+    mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value ==
+        type::custom_type,
+    OutputIt>::type {
+  using context_type = basic_format_context<OutputIt, Char>;
+  using formatter_type =
+      conditional_t<has_formatter<T, context_type>::value,
+                    typename context_type::template formatter_type<T>,
+                    fallback_formatter<T, Char>>;
+  context_type ctx(out, {}, {});
+  return formatter_type().format(value, ctx);
+}
+
+// An argument visitor that formats the argument and writes it via the output
+// iterator. It's a class and not a generic lambda for compatibility with C++11.
+template <typename OutputIt, typename Char> struct default_arg_formatter {
+  using context = basic_format_context<OutputIt, Char>;
+
+  OutputIt out;
+  basic_format_args<context> args;
+  locale_ref loc;
+
+  template <typename T> OutputIt operator()(T value) {
+    return write<Char>(out, value);
+  }
+
+  OutputIt operator()(typename basic_format_arg<context>::handle handle) {
+    basic_format_parse_context<Char> parse_ctx({});
+    basic_format_context<OutputIt, Char> format_ctx(out, args, loc);
+    handle.format(parse_ctx, format_ctx);
+    return format_ctx.out();
+  }
+};
+
+template <typename OutputIt, typename Char,
+          typename ErrorHandler = error_handler>
+class arg_formatter_base {
+ public:
+  using iterator = OutputIt;
+  using char_type = Char;
+  using format_specs = basic_format_specs<Char>;
+
+ private:
+  iterator out_;
+  locale_ref locale_;
+  format_specs* specs_;
+
+  // Attempts to reserve space for n extra characters in the output range.
+  // Returns a pointer to the reserved range or a reference to out_.
+  auto reserve(size_t n) -> decltype(detail::reserve(out_, n)) {
+    return detail::reserve(out_, n);
+  }
+
+  using reserve_iterator = remove_reference_t<decltype(
+      detail::reserve(std::declval<iterator&>(), 0))>;
+
+  template <typename T> void write_int(T value, const format_specs& spec) {
+    using uint_type = uint32_or_64_or_128_t<T>;
+    int_writer<iterator, Char, uint_type> w(out_, locale_, value, spec);
+    handle_int_type_spec(spec.type, w);
+    out_ = w.out;
   }
 
   void write(char value) {
@@ -1781,191 +2149,193 @@
     *it++ = value;
   }
 
-  template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char_type>::value)>
-  void write(Char value) {
-    auto&& it = reserve(1);
-    *it++ = value;
+  template <typename Ch, FMT_ENABLE_IF(std::is_same<Ch, Char>::value)>
+  void write(Ch value) {
+    out_ = detail::write<Char>(out_, value);
   }
 
   void write(string_view value) {
     auto&& it = reserve(value.size());
-    it = copy_str<char_type>(value.begin(), value.end(), it);
+    it = copy_str<Char>(value.begin(), value.end(), it);
   }
   void write(wstring_view value) {
-    static_assert(std::is_same<char_type, wchar_t>::value, "");
+    static_assert(std::is_same<Char, wchar_t>::value, "");
     auto&& it = reserve(value.size());
     it = std::copy(value.begin(), value.end(), it);
   }
 
-  template <typename Char>
-  void write(const Char* s, std::size_t size, const format_specs& specs) {
-    write_padded(specs, str_writer<Char>{s, size});
+  template <typename Ch>
+  void write(const Ch* s, size_t size, const format_specs& specs) {
+    auto width = specs.width != 0
+                     ? count_code_points(basic_string_view<Ch>(s, size))
+                     : 0;
+    out_ = write_padded(out_, specs, size, width, [=](reserve_iterator it) {
+      return copy_str<Char>(s, s + size, it);
+    });
   }
 
-  template <typename Char>
-  void write(basic_string_view<Char> s, const format_specs& specs = {}) {
-    const Char* data = s.data();
-    std::size_t size = s.size();
-    if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
-      size = code_point_index(s, to_unsigned(specs.precision));
-    write(data, size, specs);
-  }
-
-  template <typename UIntPtr>
-  void write_pointer(UIntPtr value, const format_specs* specs) {
-    int num_digits = count_digits<4>(value);
-    auto pw = pointer_writer<UIntPtr>{value, num_digits};
-    if (!specs) return pw(reserve(to_unsigned(num_digits) + 2));
-    format_specs specs_copy = *specs;
-    if (specs_copy.align == align::none) specs_copy.align = align::right;
-    write_padded(specs_copy, pw);
-  }
-};
-
-using writer = basic_writer<buffer_range<char>>;
-
-template <typename T> struct is_integral : std::is_integral<T> {};
-template <> struct is_integral<int128_t> : std::true_type {};
-template <> struct is_integral<uint128_t> : std::true_type {};
-
-template <typename Range, typename ErrorHandler = internal::error_handler>
-class arg_formatter_base {
- public:
-  using char_type = typename Range::value_type;
-  using iterator = typename Range::iterator;
-  using format_specs = basic_format_specs<char_type>;
-
- private:
-  using writer_type = basic_writer<Range>;
-  writer_type writer_;
-  format_specs* specs_;
-
-  struct char_writer {
-    char_type value;
-
-    size_t size() const { return 1; }
-    size_t width() const { return 1; }
-
-    template <typename It> void operator()(It&& it) const { *it++ = value; }
-  };
-
-  void write_char(char_type value) {
-    if (specs_)
-      writer_.write_padded(*specs_, char_writer{value});
-    else
-      writer_.write(value);
+  template <typename Ch>
+  void write(basic_string_view<Ch> s, const format_specs& specs = {}) {
+    out_ = detail::write(out_, s, specs);
   }
 
   void write_pointer(const void* p) {
-    writer_.write_pointer(internal::to_uintptr(p), specs_);
-  }
-
- protected:
-  writer_type& writer() { return writer_; }
-  FMT_DEPRECATED format_specs* spec() { return specs_; }
-  format_specs* specs() { return specs_; }
-  iterator out() { return writer_.out(); }
-
-  void write(bool value) {
-    string_view sv(value ? "true" : "false");
-    specs_ ? writer_.write(sv, *specs_) : writer_.write(sv);
-  }
-
-  void write(const char_type* value) {
-    if (!value) {
-      FMT_THROW(format_error("string pointer is null"));
-    } else {
-      auto length = std::char_traits<char_type>::length(value);
-      basic_string_view<char_type> sv(value, length);
-      specs_ ? writer_.write(sv, *specs_) : writer_.write(sv);
-    }
-  }
-
- public:
-  arg_formatter_base(Range r, format_specs* s, locale_ref loc)
-      : writer_(r, loc), specs_(s) {}
-
-  iterator operator()(monostate) {
-    FMT_ASSERT(false, "invalid argument type");
-    return out();
-  }
-
-  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)>
-  iterator operator()(T value) {
-    if (specs_)
-      writer_.write_int(value, *specs_);
-    else
-      writer_.write(value);
-    return out();
-  }
-
-  iterator operator()(char_type value) {
-    internal::handle_char_specs(
-        specs_, char_spec_handler(*this, static_cast<char_type>(value)));
-    return out();
-  }
-
-  iterator operator()(bool value) {
-    if (specs_ && specs_->type) return (*this)(value ? 1 : 0);
-    write(value != 0);
-    return out();
-  }
-
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  iterator operator()(T value) {
-    writer_.write(value, specs_ ? *specs_ : format_specs());
-    return out();
+    out_ = write_ptr<char_type>(out_, to_uintptr(p), specs_);
   }
 
   struct char_spec_handler : ErrorHandler {
     arg_formatter_base& formatter;
-    char_type value;
+    Char value;
 
-    char_spec_handler(arg_formatter_base& f, char_type val)
+    char_spec_handler(arg_formatter_base& f, Char val)
         : formatter(f), value(val) {}
 
     void on_int() {
-      if (formatter.specs_)
-        formatter.writer_.write_int(value, *formatter.specs_);
-      else
-        formatter.writer_.write(value);
+      // char is only formatted as int if there are specs.
+      formatter.write_int(static_cast<int>(value), *formatter.specs_);
     }
-    void on_char() { formatter.write_char(value); }
+    void on_char() {
+      if (formatter.specs_)
+        formatter.out_ = write_char(formatter.out_, value, *formatter.specs_);
+      else
+        formatter.write(value);
+    }
   };
 
-  struct cstring_spec_handler : internal::error_handler {
+  struct cstring_spec_handler : error_handler {
     arg_formatter_base& formatter;
-    const char_type* value;
+    const Char* value;
 
-    cstring_spec_handler(arg_formatter_base& f, const char_type* val)
+    cstring_spec_handler(arg_formatter_base& f, const Char* val)
         : formatter(f), value(val) {}
 
     void on_string() { formatter.write(value); }
     void on_pointer() { formatter.write_pointer(value); }
   };
 
-  iterator operator()(const char_type* value) {
-    if (!specs_) return write(value), out();
-    internal::handle_cstring_type_spec(specs_->type,
-                                       cstring_spec_handler(*this, value));
-    return out();
+ protected:
+  iterator out() { return out_; }
+  format_specs* specs() { return specs_; }
+
+  void write(bool value) {
+    if (specs_)
+      write(string_view(value ? "true" : "false"), *specs_);
+    else
+      out_ = detail::write<Char>(out_, value);
   }
 
-  iterator operator()(basic_string_view<char_type> value) {
-    if (specs_) {
-      internal::check_string_type_spec(specs_->type, internal::error_handler());
-      writer_.write(value, *specs_);
+  void write(const Char* value) {
+    if (!value) {
+      FMT_THROW(format_error("string pointer is null"));
     } else {
-      writer_.write(value);
+      auto length = std::char_traits<char_type>::length(value);
+      basic_string_view<char_type> sv(value, length);
+      specs_ ? write(sv, *specs_) : write(sv);
     }
-    return out();
+  }
+
+ public:
+  arg_formatter_base(OutputIt out, format_specs* s, locale_ref loc)
+      : out_(out), locale_(loc), specs_(s) {}
+
+  iterator operator()(monostate) {
+    FMT_ASSERT(false, "invalid argument type");
+    return out_;
+  }
+
+  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)>
+  FMT_INLINE iterator operator()(T value) {
+    if (specs_)
+      write_int(value, *specs_);
+    else
+      out_ = detail::write<Char>(out_, value);
+    return out_;
+  }
+
+  iterator operator()(Char value) {
+    handle_char_specs(specs_,
+                      char_spec_handler(*this, static_cast<Char>(value)));
+    return out_;
+  }
+
+  iterator operator()(bool value) {
+    if (specs_ && specs_->type) return (*this)(value ? 1 : 0);
+    write(value != 0);
+    return out_;
+  }
+
+  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+  iterator operator()(T value) {
+    auto specs = specs_ ? *specs_ : format_specs();
+    if (const_check(is_supported_floating_point(value)))
+      out_ = detail::write(out_, value, specs, locale_);
+    else
+      FMT_ASSERT(false, "unsupported float argument type");
+    return out_;
+  }
+
+  iterator operator()(const Char* value) {
+    if (!specs_) return write(value), out_;
+    handle_cstring_type_spec(specs_->type, cstring_spec_handler(*this, value));
+    return out_;
+  }
+
+  iterator operator()(basic_string_view<Char> value) {
+    if (specs_) {
+      check_string_type_spec(specs_->type, error_handler());
+      write(value, *specs_);
+    } else {
+      write(value);
+    }
+    return out_;
   }
 
   iterator operator()(const void* value) {
-    if (specs_)
-      check_pointer_type_spec(specs_->type, internal::error_handler());
+    if (specs_) check_pointer_type_spec(specs_->type, error_handler());
     write_pointer(value);
-    return out();
+    return out_;
+  }
+};
+
+/** The default argument formatter. */
+template <typename OutputIt, typename Char>
+class arg_formatter : public arg_formatter_base<OutputIt, Char> {
+ private:
+  using char_type = Char;
+  using base = arg_formatter_base<OutputIt, Char>;
+  using context_type = basic_format_context<OutputIt, Char>;
+
+  context_type& ctx_;
+  basic_format_parse_context<char_type>* parse_ctx_;
+  const Char* ptr_;
+
+ public:
+  using iterator = typename base::iterator;
+  using format_specs = typename base::format_specs;
+
+  /**
+    \rst
+    Constructs an argument formatter object.
+    *ctx* is a reference to the formatting context,
+    *specs* contains format specifier information for standard argument types.
+    \endrst
+   */
+  explicit arg_formatter(
+      context_type& ctx,
+      basic_format_parse_context<char_type>* parse_ctx = nullptr,
+      format_specs* specs = nullptr, const Char* ptr = nullptr)
+      : base(ctx.out(), specs, ctx.locale()),
+        ctx_(ctx),
+        parse_ctx_(parse_ctx),
+        ptr_(ptr) {}
+
+  using base::operator();
+
+  /** Formats an argument of a user-defined type. */
+  iterator operator()(typename basic_format_arg<context_type>::handle handle) {
+    if (ptr_) advance_to(*parse_ctx_, ptr_);
+    handle.format(*parse_ctx_, ctx_);
+    return ctx_.out();
   }
 };
 
@@ -1979,10 +2349,6 @@
 FMT_CONSTEXPR int parse_nonnegative_int(const Char*& begin, const Char* end,
                                         ErrorHandler&& eh) {
   FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
-  if (*begin == '0') {
-    ++begin;
-    return 0;
-  }
   unsigned value = 0;
   // Convert to unsigned to prevent a warning.
   constexpr unsigned max_int = max_value<int>();
@@ -2012,12 +2378,11 @@
                             Context& ctx)
       : parse_ctx_(parse_ctx), ctx_(ctx) {}
 
-  bool operator()(typename basic_format_arg<Context>::handle h) const {
+  void operator()(typename basic_format_arg<Context>::handle h) const {
     h.format(parse_ctx_, ctx_);
-    return true;
   }
 
-  template <typename T> bool operator()(T) const { return false; }
+  template <typename T> void operator()(T) const {}
 };
 
 template <typename T>
@@ -2076,7 +2441,9 @@
       : specs_(other.specs_) {}
 
   FMT_CONSTEXPR void on_align(align_t align) { specs_.align = align; }
-  FMT_CONSTEXPR void on_fill(Char fill) { specs_.fill[0] = fill; }
+  FMT_CONSTEXPR void on_fill(basic_string_view<Char> fill) {
+    specs_.fill = fill;
+  }
   FMT_CONSTEXPR void on_plus() { specs_.sign = sign::plus; }
   FMT_CONSTEXPR void on_minus() { specs_.sign = sign::minus; }
   FMT_CONSTEXPR void on_space() { specs_.sign = sign::space; }
@@ -2103,7 +2470,7 @@
 
 template <typename ErrorHandler> class numeric_specs_checker {
  public:
-  FMT_CONSTEXPR numeric_specs_checker(ErrorHandler& eh, internal::type arg_type)
+  FMT_CONSTEXPR numeric_specs_checker(ErrorHandler& eh, detail::type arg_type)
       : error_handler_(eh), arg_type_(arg_type) {}
 
   FMT_CONSTEXPR void require_numeric_argument() {
@@ -2113,31 +2480,37 @@
 
   FMT_CONSTEXPR void check_sign() {
     require_numeric_argument();
-    if (is_integral_type(arg_type_) && arg_type_ != int_type &&
-        arg_type_ != long_long_type && arg_type_ != internal::char_type) {
+    if (is_integral_type(arg_type_) && arg_type_ != type::int_type &&
+        arg_type_ != type::long_long_type && arg_type_ != type::char_type) {
       error_handler_.on_error("format specifier requires signed argument");
     }
   }
 
   FMT_CONSTEXPR void check_precision() {
-    if (is_integral_type(arg_type_) || arg_type_ == internal::pointer_type)
+    if (is_integral_type(arg_type_) || arg_type_ == type::pointer_type)
       error_handler_.on_error("precision not allowed for this argument type");
   }
 
  private:
   ErrorHandler& error_handler_;
-  internal::type arg_type_;
+  detail::type arg_type_;
 };
 
 // A format specifier handler that checks if specifiers are consistent with the
 // argument type.
 template <typename Handler> class specs_checker : public Handler {
+ private:
+  numeric_specs_checker<Handler> checker_;
+
+  // Suppress an MSVC warning about using this in initializer list.
+  FMT_CONSTEXPR Handler& error_handler() { return *this; }
+
  public:
-  FMT_CONSTEXPR specs_checker(const Handler& handler, internal::type arg_type)
-      : Handler(handler), checker_(*this, arg_type) {}
+  FMT_CONSTEXPR specs_checker(const Handler& handler, detail::type arg_type)
+      : Handler(handler), checker_(error_handler(), arg_type) {}
 
   FMT_CONSTEXPR specs_checker(const specs_checker& other)
-      : Handler(other), checker_(*this, other.arg_type_) {}
+      : Handler(other), checker_(error_handler(), other.arg_type_) {}
 
   FMT_CONSTEXPR void on_align(align_t align) {
     if (align == align::numeric) checker_.require_numeric_argument();
@@ -2170,9 +2543,6 @@
   }
 
   FMT_CONSTEXPR void end_precision() { checker_.check_precision(); }
-
- private:
-  numeric_specs_checker<Handler> checker_;
 };
 
 template <template <typename> class Handler, typename FormatArg,
@@ -2185,10 +2555,10 @@
 
 struct auto_id {};
 
-template <typename Context>
-FMT_CONSTEXPR typename Context::format_arg get_arg(Context& ctx, int id) {
+template <typename Context, typename ID>
+FMT_CONSTEXPR typename Context::format_arg get_arg(Context& ctx, ID id) {
   auto arg = ctx.arg(id);
-  if (!arg) ctx.on_error("argument index out of range");
+  if (!arg) ctx.on_error("argument not found");
   return arg;
 }
 
@@ -2221,17 +2591,17 @@
   using format_arg = typename Context::format_arg;
 
   FMT_CONSTEXPR format_arg get_arg(auto_id) {
-    return internal::get_arg(context_, parse_context_.next_arg_id());
+    return detail::get_arg(context_, parse_context_.next_arg_id());
   }
 
   FMT_CONSTEXPR format_arg get_arg(int arg_id) {
     parse_context_.check_arg_id(arg_id);
-    return internal::get_arg(context_, arg_id);
+    return detail::get_arg(context_, arg_id);
   }
 
   FMT_CONSTEXPR format_arg get_arg(basic_string_view<char_type> arg_id) {
     parse_context_.check_arg_id(arg_id);
-    return context_.arg(arg_id);
+    return detail::get_arg(context_, arg_id);
   }
 
   ParseContext& parse_context_;
@@ -2243,6 +2613,7 @@
 // An argument reference.
 template <typename Char> struct arg_ref {
   FMT_CONSTEXPR arg_ref() : kind(arg_id_kind::none), val() {}
+
   FMT_CONSTEXPR explicit arg_ref(int index)
       : kind(arg_id_kind::index), val(index) {}
   FMT_CONSTEXPR explicit arg_ref(basic_string_view<Char> name)
@@ -2335,7 +2706,11 @@
     return begin;
   }
   if (c >= '0' && c <= '9') {
-    int index = parse_nonnegative_int(begin, end, handler);
+    int index = 0;
+    if (c != '0')
+      index = parse_nonnegative_int(begin, end, handler);
+    else
+      ++begin;
     if (begin == end || (*begin != '}' && *begin != ':'))
       handler.on_error("invalid format string");
     else
@@ -2388,23 +2763,50 @@
   SpecHandler& handler;
 };
 
+template <typename Char>
+FMT_CONSTEXPR int code_point_length(const Char* begin) {
+  if (const_check(sizeof(Char) != 1)) return 1;
+  constexpr char lengths[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+                              0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 3, 3, 4, 0};
+  int len = lengths[static_cast<unsigned char>(*begin) >> 3];
+
+  // Compute the pointer to the next character early so that the next
+  // iteration can start working on the next character. Neither Clang
+  // nor GCC figure out this reordering on their own.
+  return len + !len;
+}
+
+template <typename Char> constexpr bool is_ascii_letter(Char c) {
+  return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
+}
+
+// Converts a character to ASCII. Returns a number > 127 on conversion failure.
+template <typename Char, FMT_ENABLE_IF(std::is_integral<Char>::value)>
+constexpr Char to_ascii(Char value) {
+  return value;
+}
+template <typename Char, FMT_ENABLE_IF(std::is_enum<Char>::value)>
+constexpr typename std::underlying_type<Char>::type to_ascii(Char value) {
+  return value;
+}
+
 // Parses fill and alignment.
 template <typename Char, typename Handler>
 FMT_CONSTEXPR const Char* parse_align(const Char* begin, const Char* end,
                                       Handler&& handler) {
   FMT_ASSERT(begin != end, "");
   auto align = align::none;
-  int i = 0;
-  if (begin + 1 != end) ++i;
-  do {
-    switch (static_cast<char>(begin[i])) {
+  auto p = begin + code_point_length(begin);
+  if (p >= end) p = begin;
+  for (;;) {
+    switch (to_ascii(*p)) {
     case '<':
       align = align::left;
       break;
     case '>':
       align = align::right;
       break;
-#if FMT_NUMERIC_ALIGN
+#if FMT_DEPRECATED_NUMERIC_ALIGN
     case '=':
       align = align::numeric;
       break;
@@ -2414,18 +2816,21 @@
       break;
     }
     if (align != align::none) {
-      if (i > 0) {
+      if (p != begin) {
         auto c = *begin;
         if (c == '{')
           return handler.on_error("invalid fill character '{'"), begin;
-        begin += 2;
-        handler.on_fill(c);
+        handler.on_fill(basic_string_view<Char>(begin, to_unsigned(p - begin)));
+        begin = p + 1;
       } else
         ++begin;
       handler.on_align(align);
       break;
+    } else if (p == begin) {
+      break;
     }
-  } while (i-- > 0);
+    p = begin;
+  }
   return begin;
 }
 
@@ -2473,13 +2878,13 @@
 template <typename Char, typename SpecHandler>
 FMT_CONSTEXPR const Char* parse_format_specs(const Char* begin, const Char* end,
                                              SpecHandler&& handler) {
-  if (begin == end || *begin == '}') return begin;
+  if (begin == end) return begin;
 
   begin = parse_align(begin, end, handler);
   if (begin == end) return begin;
 
   // Parse sign.
-  switch (static_cast<char>(*begin)) {
+  switch (to_ascii(*begin)) {
   case '+':
     handler.on_plus();
     ++begin;
@@ -2532,71 +2937,98 @@
 inline bool find<false, char>(const char* first, const char* last, char value,
                               const char*& out) {
   out = static_cast<const char*>(
-      std::memchr(first, value, internal::to_unsigned(last - first)));
+      std::memchr(first, value, detail::to_unsigned(last - first)));
   return out != nullptr;
 }
 
 template <typename Handler, typename Char> struct id_adapter {
-  FMT_CONSTEXPR void operator()() { handler.on_arg_id(); }
-  FMT_CONSTEXPR void operator()(int id) { handler.on_arg_id(id); }
+  Handler& handler;
+  int arg_id;
+
+  FMT_CONSTEXPR void operator()() { arg_id = handler.on_arg_id(); }
+  FMT_CONSTEXPR void operator()(int id) { arg_id = handler.on_arg_id(id); }
   FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
-    handler.on_arg_id(id);
+    arg_id = handler.on_arg_id(id);
   }
   FMT_CONSTEXPR void on_error(const char* message) {
     handler.on_error(message);
   }
-  Handler& handler;
 };
 
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_replacement_field(const Char* begin,
+                                                  const Char* end,
+                                                  Handler&& handler) {
+  ++begin;
+  if (begin == end) return handler.on_error("invalid format string"), end;
+  if (*begin == '}') {
+    handler.on_replacement_field(handler.on_arg_id(), begin);
+  } else if (*begin == '{') {
+    handler.on_text(begin, begin + 1);
+  } else {
+    auto adapter = id_adapter<Handler, Char>{handler, 0};
+    begin = parse_arg_id(begin, end, adapter);
+    Char c = begin != end ? *begin : Char();
+    if (c == '}') {
+      handler.on_replacement_field(adapter.arg_id, begin);
+    } else if (c == ':') {
+      begin = handler.on_format_specs(adapter.arg_id, begin + 1, end);
+      if (begin == end || *begin != '}')
+        return handler.on_error("unknown format specifier"), end;
+    } else {
+      return handler.on_error("missing '}' in format string"), end;
+    }
+  }
+  return begin + 1;
+}
+
 template <bool IS_CONSTEXPR, typename Char, typename Handler>
-FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
-                                       Handler&& handler) {
-  struct pfs_writer {
-    FMT_CONSTEXPR void operator()(const Char* begin, const Char* end) {
-      if (begin == end) return;
+FMT_CONSTEXPR_DECL FMT_INLINE void parse_format_string(
+    basic_string_view<Char> format_str, Handler&& handler) {
+  auto begin = format_str.data();
+  auto end = begin + format_str.size();
+  if (end - begin < 32) {
+    // Use a simple loop instead of memchr for small strings.
+    const Char* p = begin;
+    while (p != end) {
+      auto c = *p++;
+      if (c == '{') {
+        handler.on_text(begin, p - 1);
+        begin = p = parse_replacement_field(p - 1, end, handler);
+      } else if (c == '}') {
+        if (p == end || *p != '}')
+          return handler.on_error("unmatched '}' in format string");
+        handler.on_text(begin, p);
+        begin = ++p;
+      }
+    }
+    handler.on_text(begin, end);
+    return;
+  }
+  struct writer {
+    FMT_CONSTEXPR void operator()(const Char* pbegin, const Char* pend) {
+      if (pbegin == pend) return;
       for (;;) {
         const Char* p = nullptr;
-        if (!find<IS_CONSTEXPR>(begin, end, '}', p))
-          return handler_.on_text(begin, end);
+        if (!find<IS_CONSTEXPR>(pbegin, pend, '}', p))
+          return handler_.on_text(pbegin, pend);
         ++p;
-        if (p == end || *p != '}')
+        if (p == pend || *p != '}')
           return handler_.on_error("unmatched '}' in format string");
-        handler_.on_text(begin, p);
-        begin = p + 1;
+        handler_.on_text(pbegin, p);
+        pbegin = p + 1;
       }
     }
     Handler& handler_;
   } write{handler};
-  auto begin = format_str.data();
-  auto end = begin + format_str.size();
   while (begin != end) {
     // Doing two passes with memchr (one for '{' and another for '}') is up to
     // 2.5x faster than the naive one-pass implementation on big format strings.
     const Char* p = begin;
-    if (*begin != '{' && !find<IS_CONSTEXPR>(begin, end, '{', p))
+    if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, '{', p))
       return write(begin, end);
     write(begin, p);
-    ++p;
-    if (p == end) return handler.on_error("invalid format string");
-    if (static_cast<char>(*p) == '}') {
-      handler.on_arg_id();
-      handler.on_replacement_field(p);
-    } else if (*p == '{') {
-      handler.on_text(p, p + 1);
-    } else {
-      p = parse_arg_id(p, end, id_adapter<Handler, Char>{handler});
-      Char c = p != end ? *p : Char();
-      if (c == '}') {
-        handler.on_replacement_field(p);
-      } else if (c == ':') {
-        p = handler.on_format_specs(p + 1, end);
-        if (p == end || *p != '}')
-          return handler.on_error("unknown format specifier");
-      } else {
-        return handler.on_error("missing '}' in format string");
-      }
-    }
-    begin = p + 1;
+    begin = parse_replacement_field(p, end, handler);
   }
 }
 
@@ -2606,44 +3038,127 @@
   using char_type = typename ParseContext::char_type;
   using context = buffer_context<char_type>;
   using mapped_type =
-      conditional_t<internal::mapped_type_constant<T, context>::value !=
-                        internal::custom_type,
+      conditional_t<detail::mapped_type_constant<T, context>::value !=
+                        type::custom_type,
                     decltype(arg_mapper<context>().map(std::declval<T>())), T>;
   auto f = conditional_t<has_formatter<mapped_type, context>::value,
                          formatter<mapped_type, char_type>,
-                         internal::fallback_formatter<T, char_type>>();
+                         detail::fallback_formatter<T, char_type>>();
   return f.parse(ctx);
 }
 
+template <typename OutputIt, typename Char, typename Context>
+struct format_handler : detail::error_handler {
+  basic_format_parse_context<Char> parse_context;
+  Context context;
+
+  format_handler(OutputIt out, basic_string_view<Char> str,
+                 basic_format_args<Context> format_args, detail::locale_ref loc)
+      : parse_context(str), context(out, format_args, loc) {}
+
+  void on_text(const Char* begin, const Char* end) {
+    auto size = to_unsigned(end - begin);
+    auto out = context.out();
+    auto&& it = reserve(out, size);
+    it = std::copy_n(begin, size, it);
+    context.advance_to(out);
+  }
+
+  int on_arg_id() { return parse_context.next_arg_id(); }
+  int on_arg_id(int id) { return parse_context.check_arg_id(id), id; }
+  int on_arg_id(basic_string_view<Char> id) {
+    int arg_id = context.arg_id(id);
+    if (arg_id < 0) on_error("argument not found");
+    return arg_id;
+  }
+
+  FMT_INLINE void on_replacement_field(int id, const Char*) {
+    auto arg = get_arg(context, id);
+    context.advance_to(visit_format_arg(
+        default_arg_formatter<OutputIt, Char>{context.out(), context.args(),
+                                              context.locale()},
+        arg));
+  }
+
+  const Char* on_format_specs(int id, const Char* begin, const Char* end) {
+    auto arg = get_arg(context, id);
+    if (arg.type() == type::custom_type) {
+      advance_to(parse_context, begin);
+      visit_format_arg(custom_formatter<Context>(parse_context, context), arg);
+      return parse_context.begin();
+    }
+    auto specs = basic_format_specs<Char>();
+    if (begin + 1 < end && begin[1] == '}' && is_ascii_letter(*begin)) {
+      specs.type = static_cast<char>(*begin++);
+    } else {
+      using parse_context_t = basic_format_parse_context<Char>;
+      specs_checker<specs_handler<parse_context_t, Context>> handler(
+          specs_handler<parse_context_t, Context>(specs, parse_context,
+                                                  context),
+          arg.type());
+      begin = parse_format_specs(begin, end, handler);
+      if (begin == end || *begin != '}')
+        on_error("missing '}' in format string");
+    }
+    context.advance_to(visit_format_arg(
+        arg_formatter<OutputIt, Char>(context, &parse_context, &specs), arg));
+    return begin;
+  }
+};
+
+// A parse context with extra argument id checks. It is only used at compile
+// time because adding checks at runtime would introduce substantial overhead
+// and would be redundant since argument ids are checked when arguments are
+// retrieved anyway.
+template <typename Char, typename ErrorHandler = error_handler>
+class compile_parse_context
+    : public basic_format_parse_context<Char, ErrorHandler> {
+ private:
+  int num_args_;
+  using base = basic_format_parse_context<Char, ErrorHandler>;
+
+ public:
+  explicit FMT_CONSTEXPR compile_parse_context(
+      basic_string_view<Char> format_str, int num_args = max_value<int>(),
+      ErrorHandler eh = {})
+      : base(format_str, eh), num_args_(num_args) {}
+
+  FMT_CONSTEXPR int next_arg_id() {
+    int id = base::next_arg_id();
+    if (id >= num_args_) this->on_error("argument not found");
+    return id;
+  }
+
+  FMT_CONSTEXPR void check_arg_id(int id) {
+    base::check_arg_id(id);
+    if (id >= num_args_) this->on_error("argument not found");
+  }
+  using base::check_arg_id;
+};
+
 template <typename Char, typename ErrorHandler, typename... Args>
 class format_string_checker {
  public:
   explicit FMT_CONSTEXPR format_string_checker(
       basic_string_view<Char> format_str, ErrorHandler eh)
-      : arg_id_(max_value<unsigned>()),
-        context_(format_str, eh),
+      : context_(format_str, num_args, eh),
         parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
 
   FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
 
-  FMT_CONSTEXPR void on_arg_id() {
-    arg_id_ = context_.next_arg_id();
-    check_arg_id();
-  }
-  FMT_CONSTEXPR void on_arg_id(int id) {
-    arg_id_ = id;
-    context_.check_arg_id(id);
-    check_arg_id();
-  }
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) {
+  FMT_CONSTEXPR int on_arg_id() { return context_.next_arg_id(); }
+  FMT_CONSTEXPR int on_arg_id(int id) { return context_.check_arg_id(id), id; }
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
     on_error("compile-time checks don't support named arguments");
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_replacement_field(const Char*) {}
+  FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin, const Char*) {
+  FMT_CONSTEXPR const Char* on_format_specs(int id, const Char* begin,
+                                            const Char*) {
     advance_to(context_, begin);
-    return arg_id_ < num_args ? parse_funcs_[arg_id_](context_) : begin;
+    return id < num_args ? parse_funcs_[id](context_) : begin;
   }
 
   FMT_CONSTEXPR void on_error(const char* message) {
@@ -2651,36 +3166,66 @@
   }
 
  private:
-  using parse_context_type = basic_format_parse_context<Char, ErrorHandler>;
+  using parse_context_type = compile_parse_context<Char, ErrorHandler>;
   enum { num_args = sizeof...(Args) };
 
-  FMT_CONSTEXPR void check_arg_id() {
-    if (arg_id_ >= num_args) context_.on_error("argument index out of range");
-  }
-
   // Format specifier parsing function.
   using parse_func = const Char* (*)(parse_context_type&);
 
-  unsigned arg_id_;
   parse_context_type context_;
   parse_func parse_funcs_[num_args > 0 ? num_args : 1];
 };
 
-template <typename Char, typename ErrorHandler, typename... Args>
-FMT_CONSTEXPR bool do_check_format_string(basic_string_view<Char> s,
-                                          ErrorHandler eh = ErrorHandler()) {
-  format_string_checker<Char, ErrorHandler, Args...> checker(s, eh);
-  parse_format_string<true>(s, checker);
-  return true;
+// Converts string literals to basic_string_view.
+template <typename Char, size_t N>
+FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
+    const Char (&s)[N]) {
+  // Remove trailing null character if needed. Won't be present if this is used
+  // with raw character array (i.e. not defined as a string).
+  return {s,
+          N - ((std::char_traits<Char>::to_int_type(s[N - 1]) == 0) ? 1 : 0)};
 }
 
+// Converts string_view to basic_string_view.
+template <typename Char>
+FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
+    const std_string_view<Char>& s) {
+  return {s.data(), s.size()};
+}
+
+#define FMT_STRING_IMPL(s, base)                                  \
+  [] {                                                            \
+    /* Use a macro-like name to avoid shadowing warnings. */      \
+    struct FMT_COMPILE_STRING : base {                            \
+      using char_type = fmt::remove_cvref_t<decltype(s[0])>;      \
+      FMT_MAYBE_UNUSED FMT_CONSTEXPR                              \
+      operator fmt::basic_string_view<char_type>() const {        \
+        return fmt::detail::compile_string_to_view<char_type>(s); \
+      }                                                           \
+    };                                                            \
+    return FMT_COMPILE_STRING();                                  \
+  }()
+
+/**
+  \rst
+  Constructs a compile-time format string from a string literal *s*.
+
+  **Example**::
+
+    // A compile-time error because 'd' is an invalid specifier for strings.
+    std::string s = fmt::format(FMT_STRING("{:d}"), "foo");
+  \endrst
+ */
+#define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::compile_string)
+
 template <typename... Args, typename S,
           enable_if_t<(is_compile_string<S>::value), int>>
 void check_format_string(S format_str) {
+  FMT_CONSTEXPR_DECL auto s = to_string_view(format_str);
+  using checker = format_string_checker<typename S::char_type, error_handler,
+                                        remove_cvref_t<Args>...>;
   FMT_CONSTEXPR_DECL bool invalid_format =
-      internal::do_check_format_string<typename S::char_type,
-                                       internal::error_handler, Args...>(
-          to_string_view(format_str));
+      (parse_format_string<true>(s, checker(s, {})), true);
   (void)invalid_format;
 }
 
@@ -2691,67 +3236,34 @@
   case arg_id_kind::none:
     break;
   case arg_id_kind::index:
-    value = internal::get_dynamic_spec<Handler>(ctx.arg(ref.val.index),
-                                                ctx.error_handler());
+    value = detail::get_dynamic_spec<Handler>(ctx.arg(ref.val.index),
+                                              ctx.error_handler());
     break;
   case arg_id_kind::name:
-    value = internal::get_dynamic_spec<Handler>(ctx.arg(ref.val.name),
-                                                ctx.error_handler());
+    value = detail::get_dynamic_spec<Handler>(ctx.arg(ref.val.name),
+                                              ctx.error_handler());
     break;
   }
 }
-}  // namespace internal
 
-template <typename Range>
-using basic_writer FMT_DEPRECATED_ALIAS = internal::basic_writer<Range>;
-using writer FMT_DEPRECATED_ALIAS = internal::writer;
-using wwriter FMT_DEPRECATED_ALIAS =
-    internal::basic_writer<buffer_range<wchar_t>>;
+using format_func = void (*)(detail::buffer<char>&, int, string_view);
 
-/** The default argument formatter. */
-template <typename Range>
-class arg_formatter : public internal::arg_formatter_base<Range> {
- private:
-  using char_type = typename Range::value_type;
-  using base = internal::arg_formatter_base<Range>;
-  using context_type = basic_format_context<typename base::iterator, char_type>;
+FMT_API void format_error_code(buffer<char>& out, int error_code,
+                               string_view message) FMT_NOEXCEPT;
 
-  context_type& ctx_;
-  basic_format_parse_context<char_type>* parse_ctx_;
+FMT_API void report_error(format_func func, int error_code,
+                          string_view message) FMT_NOEXCEPT;
+}  // namespace detail
 
- public:
-  using range = Range;
-  using iterator = typename base::iterator;
-  using format_specs = typename base::format_specs;
-
-  /**
-    \rst
-    Constructs an argument formatter object.
-    *ctx* is a reference to the formatting context,
-    *specs* contains format specifier information for standard argument types.
-    \endrst
-   */
-  explicit arg_formatter(
-      context_type& ctx,
-      basic_format_parse_context<char_type>* parse_ctx = nullptr,
-      format_specs* specs = nullptr)
-      : base(Range(ctx.out()), specs, ctx.locale()),
-        ctx_(ctx),
-        parse_ctx_(parse_ctx) {}
-
-  using base::operator();
-
-  /** Formats an argument of a user-defined type. */
-  iterator operator()(typename basic_format_arg<context_type>::handle handle) {
-    handle.format(*parse_ctx_, ctx_);
-    return ctx_.out();
-  }
-};
+template <typename OutputIt, typename Char>
+using arg_formatter FMT_DEPRECATED_ALIAS =
+    detail::arg_formatter<OutputIt, Char>;
 
 /**
  An error returned by an operating system or a language runtime,
  for example a file opening error.
 */
+FMT_CLASS_API
 class FMT_API system_error : public std::runtime_error {
  private:
   void init(int err_code, string_view format_str, format_args args);
@@ -2810,7 +3322,7 @@
   may look like "Unknown error -1" and is platform-dependent.
   \endrst
  */
-FMT_API void format_system_error(internal::buffer<char>& out, int error_code,
+FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
                                  string_view message) FMT_NOEXCEPT;
 
 // Reports a system error without throwing an exception.
@@ -2818,55 +3330,6 @@
 FMT_API void report_system_error(int error_code,
                                  string_view message) FMT_NOEXCEPT;
 
-#if FMT_USE_WINDOWS_H
-
-/** A Windows error. */
-class windows_error : public system_error {
- private:
-  FMT_API void init(int error_code, string_view format_str, format_args args);
-
- public:
-  /**
-   \rst
-   Constructs a :class:`fmt::windows_error` object with the description
-   of the form
-
-   .. parsed-literal::
-     *<message>*: *<system-message>*
-
-   where *<message>* is the formatted message and *<system-message>* is the
-   system message corresponding to the error code.
-   *error_code* is a Windows error code as given by ``GetLastError``.
-   If *error_code* is not a valid error code such as -1, the system message
-   will look like "error -1".
-
-   **Example**::
-
-     // This throws a windows_error with the description
-     //   cannot open file 'madeup': The system cannot find the file specified.
-     // or similar (system message may vary).
-     const char *filename = "madeup";
-     LPOFSTRUCT of = LPOFSTRUCT();
-     HFILE file = OpenFile(filename, &of, OF_READ);
-     if (file == HFILE_ERROR) {
-       throw fmt::windows_error(GetLastError(),
-                                "cannot open file '{}'", filename);
-     }
-   \endrst
-  */
-  template <typename... Args>
-  windows_error(int error_code, string_view message, const Args&... args) {
-    init(error_code, message, make_format_args(args...));
-  }
-};
-
-// Reports a Windows error without throwing an exception.
-// Can be used to report errors from destructors.
-FMT_API void report_windows_error(int error_code,
-                                  string_view message) FMT_NOEXCEPT;
-
-#endif
-
 /** Fast integer formatter. */
 class format_int {
  private:
@@ -2876,47 +3339,32 @@
   mutable char buffer_[buffer_size];
   char* str_;
 
-  // Formats value in reverse and returns a pointer to the beginning.
-  char* format_decimal(unsigned long long value) {
-    char* ptr = buffer_ + (buffer_size - 1);  // Parens to workaround MSVC bug.
-    while (value >= 100) {
-      // Integer division is slow so do it for a group of two digits instead
-      // of for every digit. The idea comes from the talk by Alexandrescu
-      // "Three Optimization Tips for C++". See speed-test for a comparison.
-      auto index = static_cast<unsigned>((value % 100) * 2);
-      value /= 100;
-      *--ptr = internal::data::digits[index + 1];
-      *--ptr = internal::data::digits[index];
-    }
-    if (value < 10) {
-      *--ptr = static_cast<char>('0' + value);
-      return ptr;
-    }
-    auto index = static_cast<unsigned>(value * 2);
-    *--ptr = internal::data::digits[index + 1];
-    *--ptr = internal::data::digits[index];
-    return ptr;
+  template <typename UInt> char* format_unsigned(UInt value) {
+    auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
+    return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
   }
 
-  void format_signed(long long value) {
-    auto abs_value = static_cast<unsigned long long>(value);
+  template <typename Int> char* format_signed(Int value) {
+    auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
     bool negative = value < 0;
     if (negative) abs_value = 0 - abs_value;
-    str_ = format_decimal(abs_value);
-    if (negative) *--str_ = '-';
+    auto begin = format_unsigned(abs_value);
+    if (negative) *--begin = '-';
+    return begin;
   }
 
  public:
-  explicit format_int(int value) { format_signed(value); }
-  explicit format_int(long value) { format_signed(value); }
-  explicit format_int(long long value) { format_signed(value); }
-  explicit format_int(unsigned value) : str_(format_decimal(value)) {}
-  explicit format_int(unsigned long value) : str_(format_decimal(value)) {}
-  explicit format_int(unsigned long long value) : str_(format_decimal(value)) {}
+  explicit format_int(int value) : str_(format_signed(value)) {}
+  explicit format_int(long value) : str_(format_signed(value)) {}
+  explicit format_int(long long value) : str_(format_signed(value)) {}
+  explicit format_int(unsigned value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long long value)
+      : str_(format_unsigned(value)) {}
 
   /** Returns the number of characters written to the output buffer. */
-  std::size_t size() const {
-    return internal::to_unsigned(buffer_ - str_ + buffer_size - 1);
+  size_t size() const {
+    return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
   }
 
   /**
@@ -2942,59 +3390,71 @@
   std::string str() const { return std::string(str_, size()); }
 };
 
-// A formatter specialization for the core types corresponding to internal::type
+// A formatter specialization for the core types corresponding to detail::type
 // constants.
 template <typename T, typename Char>
 struct formatter<T, Char,
-                 enable_if_t<internal::type_constant<T, Char>::value !=
-                             internal::custom_type>> {
+                 enable_if_t<detail::type_constant<T, Char>::value !=
+                             detail::type::custom_type>> {
   FMT_CONSTEXPR formatter() = default;
 
   // Parses format specifiers stopping either at the end of the range or at the
   // terminating '}'.
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    using handler_type = internal::dynamic_specs_handler<ParseContext>;
-    auto type = internal::type_constant<T, Char>::value;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
-                                                  type);
+    using handler_type = detail::dynamic_specs_handler<ParseContext>;
+    auto type = detail::type_constant<T, Char>::value;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                type);
     auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
     auto eh = ctx.error_handler();
     switch (type) {
-    case internal::none_type:
-    case internal::named_arg_type:
+    case detail::type::none_type:
       FMT_ASSERT(false, "invalid argument type");
       break;
-    case internal::int_type:
-    case internal::uint_type:
-    case internal::long_long_type:
-    case internal::ulong_long_type:
-    case internal::int128_type:
-    case internal::uint128_type:
-    case internal::bool_type:
+    case detail::type::int_type:
+    case detail::type::uint_type:
+    case detail::type::long_long_type:
+    case detail::type::ulong_long_type:
+    case detail::type::int128_type:
+    case detail::type::uint128_type:
+    case detail::type::bool_type:
       handle_int_type_spec(specs_.type,
-                           internal::int_type_checker<decltype(eh)>(eh));
+                           detail::int_type_checker<decltype(eh)>(eh));
       break;
-    case internal::char_type:
+    case detail::type::char_type:
       handle_char_specs(
-          &specs_, internal::char_specs_checker<decltype(eh)>(specs_.type, eh));
+          &specs_, detail::char_specs_checker<decltype(eh)>(specs_.type, eh));
       break;
-    case internal::float_type:
-    case internal::double_type:
-    case internal::long_double_type:
-      internal::parse_float_type_spec(specs_, eh);
+    case detail::type::float_type:
+      if (detail::const_check(FMT_USE_FLOAT))
+        detail::parse_float_type_spec(specs_, eh);
+      else
+        FMT_ASSERT(false, "float support disabled");
       break;
-    case internal::cstring_type:
-      internal::handle_cstring_type_spec(
-          specs_.type, internal::cstring_type_checker<decltype(eh)>(eh));
+    case detail::type::double_type:
+      if (detail::const_check(FMT_USE_DOUBLE))
+        detail::parse_float_type_spec(specs_, eh);
+      else
+        FMT_ASSERT(false, "double support disabled");
       break;
-    case internal::string_type:
-      internal::check_string_type_spec(specs_.type, eh);
+    case detail::type::long_double_type:
+      if (detail::const_check(FMT_USE_LONG_DOUBLE))
+        detail::parse_float_type_spec(specs_, eh);
+      else
+        FMT_ASSERT(false, "long double support disabled");
       break;
-    case internal::pointer_type:
-      internal::check_pointer_type_spec(specs_.type, eh);
+    case detail::type::cstring_type:
+      detail::handle_cstring_type_spec(
+          specs_.type, detail::cstring_type_checker<decltype(eh)>(eh));
       break;
-    case internal::custom_type:
+    case detail::type::string_type:
+      detail::check_string_type_spec(specs_.type, eh);
+      break;
+    case detail::type::pointer_type:
+      detail::check_pointer_type_spec(specs_.type, eh);
+      break;
+    case detail::type::custom_type:
       // Custom format specifiers should be checked in parse functions of
       // formatter specializations.
       break;
@@ -3004,26 +3464,25 @@
 
   template <typename FormatContext>
   auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
-    using range_type =
-        internal::output_range<typename FormatContext::iterator,
-                               typename FormatContext::char_type>;
-    return visit_format_arg(arg_formatter<range_type>(ctx, nullptr, &specs_),
-                            internal::make_arg<FormatContext>(val));
+    using af = detail::arg_formatter<typename FormatContext::iterator,
+                                     typename FormatContext::char_type>;
+    return visit_format_arg(af(ctx, nullptr, &specs_),
+                            detail::make_arg<FormatContext>(val));
   }
 
  private:
-  internal::dynamic_format_specs<Char> specs_;
+  detail::dynamic_format_specs<Char> specs_;
 };
 
 #define FMT_FORMAT_AS(Type, Base)                                             \
   template <typename Char>                                                    \
   struct formatter<Type, Char> : formatter<Base, Char> {                      \
     template <typename FormatContext>                                         \
-    auto format(const Type& val, FormatContext& ctx) -> decltype(ctx.out()) { \
+    auto format(Type const& val, FormatContext& ctx) -> decltype(ctx.out()) { \
       return formatter<Base, Char>::format(val, ctx);                         \
     }                                                                         \
   }
@@ -3037,7 +3496,7 @@
 FMT_FORMAT_AS(Char*, const Char*);
 FMT_FORMAT_AS(std::basic_string<Char>, basic_string_view<Char>);
 FMT_FORMAT_AS(std::nullptr_t, const void*);
-FMT_FORMAT_AS(internal::std_string_view<Char>, basic_string_view<Char>);
+FMT_FORMAT_AS(detail::std_string_view<Char>, basic_string_view<Char>);
 
 template <typename Char>
 struct formatter<void*, Char> : formatter<const void*, Char> {
@@ -3061,13 +3520,15 @@
 //   using variant = std::variant<int, std::string>;
 //   template <>
 //   struct formatter<variant>: dynamic_formatter<> {
-//     void format(buffer &buf, const variant &v, context &ctx) {
-//       visit([&](const auto &val) { format(buf, val, ctx); }, v);
+//     auto format(const variant& v, format_context& ctx) {
+//       return visit([&](const auto& val) {
+//           return dynamic_formatter<>::format(val, ctx);
+//       }, v);
 //     }
 //   };
 template <typename Char = char> class dynamic_formatter {
  private:
-  struct null_handler : internal::error_handler {
+  struct null_handler : detail::error_handler {
     void on_align(align_t) {}
     void on_plus() {}
     void on_minus() {}
@@ -3080,16 +3541,15 @@
   auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
     format_str_ = ctx.begin();
     // Checks are deferred to formatting time when the argument type is known.
-    internal::dynamic_specs_handler<ParseContext> handler(specs_, ctx);
+    detail::dynamic_specs_handler<ParseContext> handler(specs_, ctx);
     return parse_format_specs(ctx.begin(), ctx.end(), handler);
   }
 
   template <typename T, typename FormatContext>
   auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
     handle_specs(ctx);
-    internal::specs_checker<null_handler> checker(
-        null_handler(),
-        internal::mapped_type_constant<T, FormatContext>::value);
+    detail::specs_checker<null_handler> checker(
+        null_handler(), detail::mapped_type_constant<T, FormatContext>::value);
     checker.on_align(specs_.align);
     switch (specs_.sign) {
     case sign::none:
@@ -3106,109 +3566,40 @@
     }
     if (specs_.alt) checker.on_hash();
     if (specs_.precision >= 0) checker.end_precision();
-    using range = internal::output_range<typename FormatContext::iterator,
-                                         typename FormatContext::char_type>;
-    visit_format_arg(arg_formatter<range>(ctx, nullptr, &specs_),
-                     internal::make_arg<FormatContext>(val));
+    using af = detail::arg_formatter<typename FormatContext::iterator,
+                                     typename FormatContext::char_type>;
+    visit_format_arg(af(ctx, nullptr, &specs_),
+                     detail::make_arg<FormatContext>(val));
     return ctx.out();
   }
 
  private:
   template <typename Context> void handle_specs(Context& ctx) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
   }
 
-  internal::dynamic_format_specs<Char> specs_;
+  detail::dynamic_format_specs<Char> specs_;
   const Char* format_str_;
 };
 
-template <typename Range, typename Char>
-typename basic_format_context<Range, Char>::format_arg
-basic_format_context<Range, Char>::arg(basic_string_view<char_type> name) {
-  map_.init(args_);
-  format_arg arg = map_.find(name);
-  if (arg.type() == internal::none_type) this->on_error("argument not found");
-  return arg;
-}
-
 template <typename Char, typename ErrorHandler>
 FMT_CONSTEXPR void advance_to(
     basic_format_parse_context<Char, ErrorHandler>& ctx, const Char* p) {
   ctx.advance_to(ctx.begin() + (p - &*ctx.begin()));
 }
 
-template <typename ArgFormatter, typename Char, typename Context>
-struct format_handler : internal::error_handler {
-  using range = typename ArgFormatter::range;
+/**
+  \rst
+  Converts ``p`` to ``const void*`` for pointer formatting.
 
-  format_handler(range r, basic_string_view<Char> str,
-                 basic_format_args<Context> format_args,
-                 internal::locale_ref loc)
-      : parse_context(str), context(r.begin(), format_args, loc) {}
+  **Example**::
 
-  void on_text(const Char* begin, const Char* end) {
-    auto size = internal::to_unsigned(end - begin);
-    auto out = context.out();
-    auto&& it = internal::reserve(out, size);
-    it = std::copy_n(begin, size, it);
-    context.advance_to(out);
-  }
-
-  void get_arg(int id) { arg = internal::get_arg(context, id); }
-
-  void on_arg_id() { get_arg(parse_context.next_arg_id()); }
-  void on_arg_id(int id) {
-    parse_context.check_arg_id(id);
-    get_arg(id);
-  }
-  void on_arg_id(basic_string_view<Char> id) { arg = context.arg(id); }
-
-  void on_replacement_field(const Char* p) {
-    advance_to(parse_context, p);
-    context.advance_to(
-        visit_format_arg(ArgFormatter(context, &parse_context), arg));
-  }
-
-  const Char* on_format_specs(const Char* begin, const Char* end) {
-    advance_to(parse_context, begin);
-    internal::custom_formatter<Context> f(parse_context, context);
-    if (visit_format_arg(f, arg)) return parse_context.begin();
-    basic_format_specs<Char> specs;
-    using internal::specs_handler;
-    using parse_context_t = basic_format_parse_context<Char>;
-    internal::specs_checker<specs_handler<parse_context_t, Context>> handler(
-        specs_handler<parse_context_t, Context>(specs, parse_context, context),
-        arg.type());
-    begin = parse_format_specs(begin, end, handler);
-    if (begin == end || *begin != '}') on_error("missing '}' in format string");
-    advance_to(parse_context, begin);
-    context.advance_to(
-        visit_format_arg(ArgFormatter(context, &parse_context, &specs), arg));
-    return begin;
-  }
-
-  basic_format_parse_context<Char> parse_context;
-  Context context;
-  basic_format_arg<Context> arg;
-};
-
-/** Formats arguments and writes the output to the range. */
-template <typename ArgFormatter, typename Char, typename Context>
-typename Context::iterator vformat_to(
-    typename ArgFormatter::range out, basic_string_view<Char> format_str,
-    basic_format_args<Context> args,
-    internal::locale_ref loc = internal::locale_ref()) {
-  format_handler<ArgFormatter, Char, Context> h(out, format_str, args, loc);
-  internal::parse_format_string<false>(format_str, h);
-  return h.context.out();
-}
-
-// Casts ``p`` to ``const void*`` for pointer formatting.
-// Example:
-//   auto s = format("{}", ptr(p));
+    auto s = fmt::format("{}", fmt::ptr(p));
+  \endrst
+ */
 template <typename T> inline const void* ptr(const T* p) { return p; }
 template <typename T> inline const void* ptr(const std::unique_ptr<T>& p) {
   return p.get();
@@ -3217,19 +3608,55 @@
   return p.get();
 }
 
-template <typename It, typename Char> struct arg_join : internal::view {
-  It begin;
-  It end;
-  basic_string_view<Char> sep;
+class bytes {
+ private:
+  string_view data_;
+  friend struct formatter<bytes>;
 
-  arg_join(It b, It e, basic_string_view<Char> s) : begin(b), end(e), sep(s) {}
+ public:
+  explicit bytes(string_view data) : data_(data) {}
 };
 
-template <typename It, typename Char>
-struct formatter<arg_join<It, Char>, Char>
+template <> struct formatter<bytes> {
+ private:
+  detail::dynamic_format_specs<char> specs_;
+
+ public:
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    using handler_type = detail::dynamic_specs_handler<ParseContext>;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                detail::type::string_type);
+    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
+    detail::check_string_type_spec(specs_.type, ctx.error_handler());
+    return it;
+  }
+
+  template <typename FormatContext>
+  auto format(bytes b, FormatContext& ctx) -> decltype(ctx.out()) {
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
+        specs_.precision, specs_.precision_ref, ctx);
+    return detail::write_bytes(ctx.out(), b.data_, specs_);
+  }
+};
+
+template <typename It, typename Sentinel, typename Char>
+struct arg_join : detail::view {
+  It begin;
+  Sentinel end;
+  basic_string_view<Char> sep;
+
+  arg_join(It b, Sentinel e, basic_string_view<Char> s)
+      : begin(b), end(e), sep(s) {}
+};
+
+template <typename It, typename Sentinel, typename Char>
+struct formatter<arg_join<It, Sentinel, Char>, Char>
     : formatter<typename std::iterator_traits<It>::value_type, Char> {
   template <typename FormatContext>
-  auto format(const arg_join<It, Char>& value, FormatContext& ctx)
+  auto format(const arg_join<It, Sentinel, Char>& value, FormatContext& ctx)
       -> decltype(ctx.out()) {
     using base = formatter<typename std::iterator_traits<It>::value_type, Char>;
     auto it = value.begin;
@@ -3250,13 +3677,13 @@
   Returns an object that formats the iterator range `[begin, end)` with elements
   separated by `sep`.
  */
-template <typename It>
-arg_join<It, char> join(It begin, It end, string_view sep) {
+template <typename It, typename Sentinel>
+arg_join<It, Sentinel, char> join(It begin, Sentinel end, string_view sep) {
   return {begin, end, sep};
 }
 
-template <typename It>
-arg_join<It, wchar_t> join(It begin, It end, wstring_view sep) {
+template <typename It, typename Sentinel>
+arg_join<It, Sentinel, wchar_t> join(It begin, Sentinel end, wstring_view sep) {
   return {begin, end, sep};
 }
 
@@ -3269,24 +3696,28 @@
     std::vector<int> v = {1, 2, 3};
     fmt::print("{}", fmt::join(v, ", "));
     // Output: "1, 2, 3"
+
+  ``fmt::join`` applies passed format specifiers to the range elements::
+
+    fmt::print("{:02}", fmt::join(v, ", "));
+    // Output: "01, 02, 03"
   \endrst
  */
 template <typename Range>
-arg_join<internal::iterator_t<const Range>, char> join(const Range& range,
-                                                       string_view sep) {
+arg_join<detail::iterator_t<Range>, detail::sentinel_t<Range>, char> join(
+    Range&& range, string_view sep) {
   return join(std::begin(range), std::end(range), sep);
 }
 
 template <typename Range>
-arg_join<internal::iterator_t<const Range>, wchar_t> join(const Range& range,
-                                                          wstring_view sep) {
+arg_join<detail::iterator_t<Range>, detail::sentinel_t<Range>, wchar_t> join(
+    Range&& range, wstring_view sep) {
   return join(std::begin(range), std::end(range), sep);
 }
 
 /**
   \rst
   Converts *value* to ``std::string`` using the default format for type *T*.
-  It doesn't support user-defined types with custom formatters.
 
   **Example**::
 
@@ -3295,8 +3726,21 @@
     std::string answer = fmt::to_string(42);
   \endrst
  */
-template <typename T> inline std::string to_string(const T& value) {
-  return format("{}", value);
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+inline std::string to_string(const T& value) {
+  std::string result;
+  detail::write<char>(std::back_inserter(result), value);
+  return result;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline std::string to_string(T value) {
+  // The buffer should be large enough to store the number including the sign or
+  // "false" for bool.
+  constexpr int max_size = detail::digits10<T>() + 2;
+  char buffer[max_size > 5 ? static_cast<unsigned>(max_size) : 5];
+  char* begin = buffer;
+  return std::string(begin, detail::write<char>(begin, value));
 }
 
 /**
@@ -3306,36 +3750,76 @@
   return format(L"{}", value);
 }
 
-template <typename Char, std::size_t SIZE>
+template <typename Char, size_t SIZE>
 std::basic_string<Char> to_string(const basic_memory_buffer<Char, SIZE>& buf) {
-  return std::basic_string<Char>(buf.data(), buf.size());
+  auto size = buf.size();
+  detail::assume(size < std::basic_string<Char>().max_size());
+  return std::basic_string<Char>(buf.data(), size);
 }
 
 template <typename Char>
-typename buffer_context<Char>::iterator internal::vformat_to(
-    internal::buffer<Char>& buf, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<Char>> args) {
-  using range = buffer_range<Char>;
-  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str),
-                                          args);
+void detail::vformat_to(
+    detail::buffer<Char>& buf, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args,
+    detail::locale_ref loc) {
+  using iterator = typename buffer_context<Char>::iterator;
+  auto out = buffer_appender<Char>(buf);
+  if (format_str.size() == 2 && equal2(format_str.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) error_handler().on_error("argument not found");
+    visit_format_arg(default_arg_formatter<iterator, Char>{out, args, loc},
+                     arg);
+    return;
+  }
+  format_handler<iterator, Char, buffer_context<Char>> h(out, format_str, args,
+                                                         loc);
+  parse_format_string<false>(format_str, h);
 }
 
+#ifndef FMT_HEADER_ONLY
+extern template void detail::vformat_to(detail::buffer<char>&, string_view,
+                                        basic_format_args<format_context>,
+                                        detail::locale_ref);
+namespace detail {
+
+extern template FMT_API std::string grouping_impl<char>(locale_ref loc);
+extern template FMT_API std::string grouping_impl<wchar_t>(locale_ref loc);
+extern template FMT_API char thousands_sep_impl<char>(locale_ref loc);
+extern template FMT_API wchar_t thousands_sep_impl<wchar_t>(locale_ref loc);
+extern template FMT_API char decimal_point_impl(locale_ref loc);
+extern template FMT_API wchar_t decimal_point_impl(locale_ref loc);
+extern template int format_float<double>(double value, int precision,
+                                         float_specs specs, buffer<char>& buf);
+extern template int format_float<long double>(long double value, int precision,
+                                              float_specs specs,
+                                              buffer<char>& buf);
+int snprintf_float(float value, int precision, float_specs specs,
+                   buffer<char>& buf) = delete;
+extern template int snprintf_float<double>(double value, int precision,
+                                           float_specs specs,
+                                           buffer<char>& buf);
+extern template int snprintf_float<long double>(long double value,
+                                                int precision,
+                                                float_specs specs,
+                                                buffer<char>& buf);
+}  // namespace detail
+#endif
+
 template <typename S, typename Char = char_t<S>,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
-inline typename buffer_context<Char>::iterator vformat_to(
-    internal::buffer<Char>& buf, const S& format_str,
-    basic_format_args<buffer_context<Char>> args) {
-  return internal::vformat_to(buf, to_string_view(format_str), args);
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
+inline void vformat_to(
+    detail::buffer<Char>& buf, const S& format_str,
+    basic_format_args<FMT_BUFFER_CONTEXT(type_identity_t<Char>)> args) {
+  return detail::vformat_to(buf, to_string_view(format_str), args);
 }
 
-template <typename S, typename... Args, std::size_t SIZE = inline_buffer_size,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+template <typename S, typename... Args, size_t SIZE = inline_buffer_size,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline typename buffer_context<Char>::iterator format_to(
     basic_memory_buffer<Char, SIZE>& buf, const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = buffer_context<Char>;
-  return internal::vformat_to(buf, to_string_view(format_str),
-                              {make_format_args<context>(args...)});
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  detail::vformat_to(buf, to_string_view(format_str), vargs);
+  return detail::buffer_appender<Char>(buf);
 }
 
 template <typename OutputIt, typename Char = char>
@@ -3344,113 +3828,33 @@
 template <typename OutputIt, typename Char = char>
 using format_args_t = basic_format_args<format_context_t<OutputIt, Char>>;
 
-template <typename S, typename OutputIt, typename... Args,
-          FMT_ENABLE_IF(
-              internal::is_output_iterator<OutputIt>::value &&
-              !internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
-inline OutputIt vformat_to(OutputIt out, const S& format_str,
-                           format_args_t<OutputIt, char_t<S>> args) {
-  using range = internal::output_range<OutputIt, char_t<S>>;
-  return vformat_to<arg_formatter<range>>(range(out),
-                                          to_string_view(format_str), args);
-}
-
-/**
- \rst
- Formats arguments, writes the result to the output iterator ``out`` and returns
- the iterator past the end of the output range.
-
- **Example**::
-
-   std::vector<char> out;
-   fmt::format_to(std::back_inserter(out), "{}", 42);
- \endrst
- */
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(
-              internal::is_output_iterator<OutputIt>::value &&
-              !internal::is_contiguous_back_insert_iterator<OutputIt>::value &&
-              internal::is_string<S>::value)>
-inline OutputIt format_to(OutputIt out, const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = format_context_t<OutputIt, char_t<S>>;
-  return vformat_to(out, to_string_view(format_str),
-                    {make_format_args<context>(args...)});
-}
-
-template <typename OutputIt> struct format_to_n_result {
-  /** Iterator past the end of the output range. */
-  OutputIt out;
-  /** Total (not truncated) output size. */
-  std::size_t size;
-};
+template <typename OutputIt, typename Char = typename OutputIt::value_type>
+using format_to_n_context FMT_DEPRECATED_ALIAS = buffer_context<Char>;
 
 template <typename OutputIt, typename Char = typename OutputIt::value_type>
-using format_to_n_context =
-    format_context_t<internal::truncating_iterator<OutputIt>, Char>;
-
-template <typename OutputIt, typename Char = typename OutputIt::value_type>
-using format_to_n_args = basic_format_args<format_to_n_context<OutputIt, Char>>;
+using format_to_n_args FMT_DEPRECATED_ALIAS =
+    basic_format_args<buffer_context<Char>>;
 
 template <typename OutputIt, typename Char, typename... Args>
-inline format_arg_store<format_to_n_context<OutputIt, Char>, Args...>
+FMT_DEPRECATED format_arg_store<buffer_context<Char>, Args...>
 make_format_to_n_args(const Args&... args) {
-  return format_arg_store<format_to_n_context<OutputIt, Char>, Args...>(
-      args...);
+  return format_arg_store<buffer_context<Char>, Args...>(args...);
 }
 
-template <typename OutputIt, typename Char, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value)>
-inline format_to_n_result<OutputIt> vformat_to_n(
-    OutputIt out, std::size_t n, basic_string_view<Char> format_str,
-    format_to_n_args<OutputIt, Char> args) {
-  auto it = vformat_to(internal::truncating_iterator<OutputIt>(out, n),
-                       format_str, args);
-  return {it.base(), it.count()};
-}
-
-/**
- \rst
- Formats arguments, writes up to ``n`` characters of the result to the output
- iterator ``out`` and returns the total output size and the iterator past the
- end of the output range.
- \endrst
- */
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value&&
-                            internal::is_output_iterator<OutputIt>::value)>
-inline format_to_n_result<OutputIt> format_to_n(OutputIt out, std::size_t n,
-                                                const S& format_str,
-                                                const Args&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = format_to_n_context<OutputIt, char_t<S>>;
-  return vformat_to_n(out, n, to_string_view(format_str),
-                      {make_format_args<context>(args...)});
-}
-
-template <typename Char>
-inline std::basic_string<Char> internal::vformat(
+template <typename Char, enable_if_t<(!std::is_same<Char, char>::value), int>>
+std::basic_string<Char> detail::vformat(
     basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<Char>> args) {
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  internal::vformat_to(buffer, format_str, args);
+  detail::vformat_to(buffer, format_str, args);
   return to_string(buffer);
 }
 
-/**
-  Returns the number of characters in the output of
-  ``format(format_str, args...)``.
- */
-template <typename... Args>
-inline std::size_t formatted_size(string_view format_str, const Args&... args) {
-  return format_to(internal::counting_iterator(), format_str, args...).count();
-}
-
 template <typename Char, FMT_ENABLE_IF(std::is_same<Char, wchar_t>::value)>
 void vprint(std::FILE* f, basic_string_view<Char> format_str,
             wformat_args args) {
   wmemory_buffer buffer;
-  internal::vformat_to(buffer, format_str, args);
+  detail::vformat_to(buffer, format_str, args);
   buffer.push_back(L'\0');
   if (std::fputws(buffer.data(), f) == -1)
     FMT_THROW(system_error(errno, "cannot write to file"));
@@ -3462,19 +3866,15 @@
 }
 
 #if FMT_USE_USER_DEFINED_LITERALS
-namespace internal {
+namespace detail {
 
 #  if FMT_USE_UDL_TEMPLATE
 template <typename Char, Char... CHARS> class udl_formatter {
  public:
   template <typename... Args>
   std::basic_string<Char> operator()(Args&&... args) const {
-    FMT_CONSTEXPR_DECL Char s[] = {CHARS..., '\0'};
-    FMT_CONSTEXPR_DECL bool invalid_format =
-        do_check_format_string<Char, error_handler, remove_cvref_t<Args>...>(
-            basic_string_view<Char>(s, sizeof...(CHARS)));
-    (void)invalid_format;
-    return format(s, std::forward<Args>(args)...);
+    static FMT_CONSTEXPR_DECL Char s[] = {CHARS..., '\0'};
+    return format(FMT_STRING(s), std::forward<Args>(args)...);
   }
 };
 #  else
@@ -3489,23 +3889,23 @@
 #  endif  // FMT_USE_UDL_TEMPLATE
 
 template <typename Char> struct udl_arg {
-  basic_string_view<Char> str;
+  const Char* str;
 
-  template <typename T> named_arg<T, Char> operator=(T&& value) const {
+  template <typename T> named_arg<Char, T> operator=(T&& value) const {
     return {str, std::forward<T>(value)};
   }
 };
-
-}  // namespace internal
+}  // namespace detail
 
 inline namespace literals {
 #  if FMT_USE_UDL_TEMPLATE
 #    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wpedantic"
 #    if FMT_CLANG_VERSION
 #      pragma GCC diagnostic ignored "-Wgnu-string-literal-operator-template"
 #    endif
 template <typename Char, Char... CHARS>
-FMT_CONSTEXPR internal::udl_formatter<Char, CHARS...> operator""_format() {
+FMT_CONSTEXPR detail::udl_formatter<Char, CHARS...> operator""_format() {
   return {};
 }
 #    pragma GCC diagnostic pop
@@ -3520,12 +3920,12 @@
     std::string message = "The answer is {}"_format(42);
   \endrst
  */
-FMT_CONSTEXPR internal::udl_formatter<char> operator"" _format(const char* s,
-                                                               std::size_t n) {
+FMT_CONSTEXPR detail::udl_formatter<char> operator"" _format(const char* s,
+                                                             size_t n) {
   return {{s, n}};
 }
-FMT_CONSTEXPR internal::udl_formatter<wchar_t> operator"" _format(
-    const wchar_t* s, std::size_t n) {
+FMT_CONSTEXPR detail::udl_formatter<wchar_t> operator"" _format(
+    const wchar_t* s, size_t n) {
   return {{s, n}};
 }
 #  endif  // FMT_USE_UDL_TEMPLATE
@@ -3540,50 +3940,16 @@
     fmt::print("Elapsed time: {s:.2f} seconds", "s"_a=1.23);
   \endrst
  */
-FMT_CONSTEXPR internal::udl_arg<char> operator"" _a(const char* s,
-                                                    std::size_t n) {
-  return {{s, n}};
+FMT_CONSTEXPR detail::udl_arg<char> operator"" _a(const char* s, size_t) {
+  return {s};
 }
-FMT_CONSTEXPR internal::udl_arg<wchar_t> operator"" _a(const wchar_t* s,
-                                                       std::size_t n) {
-  return {{s, n}};
+FMT_CONSTEXPR detail::udl_arg<wchar_t> operator"" _a(const wchar_t* s, size_t) {
+  return {s};
 }
 }  // namespace literals
 #endif  // FMT_USE_USER_DEFINED_LITERALS
 FMT_END_NAMESPACE
 
-#define FMT_STRING_IMPL(s, ...)                                         \
-  [] {                                                                  \
-    struct str : fmt::compile_string {                                  \
-      using char_type = typename std::remove_cv<std::remove_pointer<    \
-          typename std::decay<decltype(s)>::type>::type>::type;         \
-      __VA_ARGS__ FMT_CONSTEXPR                                         \
-      operator fmt::basic_string_view<char_type>() const {              \
-        return {s, sizeof(s) / sizeof(char_type) - 1};                  \
-      }                                                                 \
-    } result;                                                           \
-    /* Suppress Qt Creator warning about unused operator. */            \
-    (void)static_cast<fmt::basic_string_view<typename str::char_type>>( \
-        result);                                                        \
-    return result;                                                      \
-  }()
-
-/**
-  \rst
-  Constructs a compile-time format string.
-
-  **Example**::
-
-    // A compile-time error because 'd' is an invalid specifier for strings.
-    std::string s = format(FMT_STRING("{:d}"), "foo");
-  \endrst
- */
-#define FMT_STRING(s) FMT_STRING_IMPL(s, )
-
-#if defined(FMT_STRING_ALIAS) && FMT_STRING_ALIAS
-#  define fmt(s) FMT_STRING_IMPL(s, [[deprecated]])
-#endif
-
 #ifdef FMT_HEADER_ONLY
 #  define FMT_FUNC inline
 #  include "format-inl.h"
diff --git a/include/fmt/locale.h b/include/fmt/locale.h
index 7c13656..7301bf9 100644
--- a/include/fmt/locale.h
+++ b/include/fmt/locale.h
@@ -9,67 +9,54 @@
 #define FMT_LOCALE_H_
 
 #include <locale>
+
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
 
-namespace internal {
+namespace detail {
 template <typename Char>
-typename buffer_context<Char>::iterator vformat_to(
-    const std::locale& loc, buffer<Char>& buf,
-    basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<Char>> args) {
-  using range = buffer_range<Char>;
-  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str), args,
-                                          internal::locale_ref(loc));
-}
-
-template <typename Char>
-std::basic_string<Char> vformat(const std::locale& loc,
-                                basic_string_view<Char> format_str,
-                                basic_format_args<buffer_context<Char>> args) {
+std::basic_string<Char> vformat(
+    const std::locale& loc, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  internal::vformat_to(loc, buffer, format_str, args);
+  detail::vformat_to(buffer, format_str, args, detail::locale_ref(loc));
   return fmt::to_string(buffer);
 }
-}  // namespace internal
+}  // namespace detail
 
 template <typename S, typename Char = char_t<S>>
 inline std::basic_string<Char> vformat(
     const std::locale& loc, const S& format_str,
-    basic_format_args<buffer_context<Char>> args) {
-  return internal::vformat(loc, to_string_view(format_str), args);
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  return detail::vformat(loc, to_string_view(format_str), args);
 }
 
 template <typename S, typename... Args, typename Char = char_t<S>>
 inline std::basic_string<Char> format(const std::locale& loc,
                                       const S& format_str, Args&&... args) {
-  return internal::vformat(
-      loc, to_string_view(format_str),
-      {internal::make_args_checked<Args...>(format_str, args...)});
+  return detail::vformat(loc, to_string_view(format_str),
+                         fmt::make_args_checked<Args...>(format_str, args...));
 }
 
 template <typename S, typename OutputIt, typename... Args,
-          typename Char = enable_if_t<
-              internal::is_output_iterator<OutputIt>::value, char_t<S>>>
-inline OutputIt vformat_to(OutputIt out, const std::locale& loc,
-                           const S& format_str,
-                           format_args_t<OutputIt, Char> args) {
-  using range = internal::output_range<OutputIt, Char>;
-  return vformat_to<arg_formatter<range>>(
-      range(out), to_string_view(format_str), args, internal::locale_ref(loc));
+          typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
+inline OutputIt vformat_to(
+    OutputIt out, const std::locale& loc, const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+  decltype(detail::get_buffer<Char>(out)) buf(detail::get_buffer_init(out));
+  vformat_to(buf, to_string_view(format_str), args, detail::locale_ref(loc));
+  return detail::get_iterator(buf);
 }
 
 template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value&&
-                            internal::is_string<S>::value)>
-inline OutputIt format_to(OutputIt out, const std::locale& loc,
-                          const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = format_context_t<OutputIt, char_t<S>>;
-  format_arg_store<context, Args...> as{args...};
-  return vformat_to(out, loc, to_string_view(format_str),
-                    basic_format_args<context>(as));
+          bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value>
+inline auto format_to(OutputIt out, const std::locale& loc,
+                      const S& format_str, Args&&... args) ->
+    typename std::enable_if<enable, OutputIt>::type {
+  const auto& vargs = fmt::make_args_checked<Args...>(format_str, args...);
+  return vformat_to(out, loc, to_string_view(format_str), vargs);
 }
 
 FMT_END_NAMESPACE
diff --git a/include/fmt/os.h b/include/fmt/os.h
new file mode 100644
index 0000000..d44ea0c
--- /dev/null
+++ b/include/fmt/os.h
@@ -0,0 +1,480 @@
+// Formatting library for C++ - optional OS-specific functionality
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_OS_H_
+#define FMT_OS_H_
+
+#if defined(__MINGW32__) || defined(__CYGWIN__)
+// Workaround MinGW bug https://sourceforge.net/p/mingw/bugs/2024/.
+#  undef __STRICT_ANSI__
+#endif
+
+#include <cerrno>
+#include <clocale>  // for locale_t
+#include <cstddef>
+#include <cstdio>
+#include <cstdlib>  // for strtod_l
+
+#if defined __APPLE__ || defined(__FreeBSD__)
+#  include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
+#endif
+
+#include "format.h"
+
+// UWP doesn't provide _pipe.
+#if FMT_HAS_INCLUDE("winapifamily.h")
+#  include <winapifamily.h>
+#endif
+#if (FMT_HAS_INCLUDE(<fcntl.h>) || defined(__APPLE__) || \
+     defined(__linux__)) &&                              \
+    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#  include <fcntl.h>  // for O_RDONLY
+#  define FMT_USE_FCNTL 1
+#else
+#  define FMT_USE_FCNTL 0
+#endif
+
+#ifndef FMT_POSIX
+#  if defined(_WIN32) && !defined(__MINGW32__)
+// Fix warnings about deprecated symbols.
+#    define FMT_POSIX(call) _##call
+#  else
+#    define FMT_POSIX(call) call
+#  endif
+#endif
+
+// Calls to system functions are wrapped in FMT_SYSTEM for testability.
+#ifdef FMT_SYSTEM
+#  define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
+#else
+#  define FMT_SYSTEM(call) ::call
+#  ifdef _WIN32
+// Fix warnings about deprecated symbols.
+#    define FMT_POSIX_CALL(call) ::_##call
+#  else
+#    define FMT_POSIX_CALL(call) ::call
+#  endif
+#endif
+
+// Retries the expression while it evaluates to error_result and errno
+// equals to EINTR.
+#ifndef _WIN32
+#  define FMT_RETRY_VAL(result, expression, error_result) \
+    do {                                                  \
+      (result) = (expression);                            \
+    } while ((result) == (error_result) && errno == EINTR)
+#else
+#  define FMT_RETRY_VAL(result, expression, error_result) result = (expression)
+#endif
+
+#define FMT_RETRY(result, expression) FMT_RETRY_VAL(result, expression, -1)
+
+FMT_BEGIN_NAMESPACE
+
+/**
+  \rst
+  A reference to a null-terminated string. It can be constructed from a C
+  string or ``std::string``.
+
+  You can use one of the following type aliases for common character types:
+
+  +---------------+-----------------------------+
+  | Type          | Definition                  |
+  +===============+=============================+
+  | cstring_view  | basic_cstring_view<char>    |
+  +---------------+-----------------------------+
+  | wcstring_view | basic_cstring_view<wchar_t> |
+  +---------------+-----------------------------+
+
+  This class is most useful as a parameter type to allow passing
+  different types of strings to a function, for example::
+
+    template <typename... Args>
+    std::string format(cstring_view format_str, const Args & ... args);
+
+    format("{}", 42);
+    format(std::string("{}"), 42);
+  \endrst
+ */
+template <typename Char> class basic_cstring_view {
+ private:
+  const Char* data_;
+
+ public:
+  /** Constructs a string reference object from a C string. */
+  basic_cstring_view(const Char* s) : data_(s) {}
+
+  /**
+    \rst
+    Constructs a string reference from an ``std::string`` object.
+    \endrst
+   */
+  basic_cstring_view(const std::basic_string<Char>& s) : data_(s.c_str()) {}
+
+  /** Returns the pointer to a C string. */
+  const Char* c_str() const { return data_; }
+};
+
+using cstring_view = basic_cstring_view<char>;
+using wcstring_view = basic_cstring_view<wchar_t>;
+
+// An error code.
+class error_code {
+ private:
+  int value_;
+
+ public:
+  explicit error_code(int value = 0) FMT_NOEXCEPT : value_(value) {}
+
+  int get() const FMT_NOEXCEPT { return value_; }
+};
+
+#ifdef _WIN32
+namespace detail {
+// A converter from UTF-16 to UTF-8.
+// It is only provided for Windows since other systems support UTF-8 natively.
+class utf16_to_utf8 {
+ private:
+  memory_buffer buffer_;
+
+ public:
+  utf16_to_utf8() {}
+  FMT_API explicit utf16_to_utf8(wstring_view s);
+  operator string_view() const { return string_view(&buffer_[0], size()); }
+  size_t size() const { return buffer_.size() - 1; }
+  const char* c_str() const { return &buffer_[0]; }
+  std::string str() const { return std::string(&buffer_[0], size()); }
+
+  // Performs conversion returning a system error code instead of
+  // throwing exception on conversion error. This method may still throw
+  // in case of memory allocation error.
+  FMT_API int convert(wstring_view s);
+};
+
+FMT_API void format_windows_error(buffer<char>& out, int error_code,
+                                  string_view message) FMT_NOEXCEPT;
+}  // namespace detail
+
+/** A Windows error. */
+class windows_error : public system_error {
+ private:
+  FMT_API void init(int error_code, string_view format_str, format_args args);
+
+ public:
+  /**
+   \rst
+   Constructs a :class:`fmt::windows_error` object with the description
+   of the form
+
+   .. parsed-literal::
+     *<message>*: *<system-message>*
+
+   where *<message>* is the formatted message and *<system-message>* is the
+   system message corresponding to the error code.
+   *error_code* is a Windows error code as given by ``GetLastError``.
+   If *error_code* is not a valid error code such as -1, the system message
+   will look like "error -1".
+
+   **Example**::
+
+     // This throws a windows_error with the description
+     //   cannot open file 'madeup': The system cannot find the file specified.
+     // or similar (system message may vary).
+     const char *filename = "madeup";
+     LPOFSTRUCT of = LPOFSTRUCT();
+     HFILE file = OpenFile(filename, &of, OF_READ);
+     if (file == HFILE_ERROR) {
+       throw fmt::windows_error(GetLastError(),
+                                "cannot open file '{}'", filename);
+     }
+   \endrst
+  */
+  template <typename... Args>
+  windows_error(int error_code, string_view message, const Args&... args) {
+    init(error_code, message, make_format_args(args...));
+  }
+};
+
+// Reports a Windows error without throwing an exception.
+// Can be used to report errors from destructors.
+FMT_API void report_windows_error(int error_code,
+                                  string_view message) FMT_NOEXCEPT;
+#endif  // _WIN32
+
+// A buffered file.
+class buffered_file {
+ private:
+  FILE* file_;
+
+  friend class file;
+
+  explicit buffered_file(FILE* f) : file_(f) {}
+
+ public:
+  buffered_file(const buffered_file&) = delete;
+  void operator=(const buffered_file&) = delete;
+
+  // Constructs a buffered_file object which doesn't represent any file.
+  buffered_file() FMT_NOEXCEPT : file_(nullptr) {}
+
+  // Destroys the object closing the file it represents if any.
+  FMT_API ~buffered_file() FMT_NOEXCEPT;
+
+ public:
+  buffered_file(buffered_file&& other) FMT_NOEXCEPT : file_(other.file_) {
+    other.file_ = nullptr;
+  }
+
+  buffered_file& operator=(buffered_file&& other) {
+    close();
+    file_ = other.file_;
+    other.file_ = nullptr;
+    return *this;
+  }
+
+  // Opens a file.
+  FMT_API buffered_file(cstring_view filename, cstring_view mode);
+
+  // Closes the file.
+  FMT_API void close();
+
+  // Returns the pointer to a FILE object representing this file.
+  FILE* get() const FMT_NOEXCEPT { return file_; }
+
+  // We place parentheses around fileno to workaround a bug in some versions
+  // of MinGW that define fileno as a macro.
+  FMT_API int(fileno)() const;
+
+  void vprint(string_view format_str, format_args args) {
+    fmt::vprint(file_, format_str, args);
+  }
+
+  template <typename... Args>
+  inline void print(string_view format_str, const Args&... args) {
+    vprint(format_str, make_format_args(args...));
+  }
+};
+
+#if FMT_USE_FCNTL
+// A file. Closed file is represented by a file object with descriptor -1.
+// Methods that are not declared with FMT_NOEXCEPT may throw
+// fmt::system_error in case of failure. Note that some errors such as
+// closing the file multiple times will cause a crash on Windows rather
+// than an exception. You can get standard behavior by overriding the
+// invalid parameter handler with _set_invalid_parameter_handler.
+class file {
+ private:
+  int fd_;  // File descriptor.
+
+  // Constructs a file object with a given descriptor.
+  explicit file(int fd) : fd_(fd) {}
+
+ public:
+  // Possible values for the oflag argument to the constructor.
+  enum {
+    RDONLY = FMT_POSIX(O_RDONLY),  // Open for reading only.
+    WRONLY = FMT_POSIX(O_WRONLY),  // Open for writing only.
+    RDWR = FMT_POSIX(O_RDWR),      // Open for reading and writing.
+    CREATE = FMT_POSIX(O_CREAT),   // Create if the file doesn't exist.
+    APPEND = FMT_POSIX(O_APPEND)   // Open in append mode.
+  };
+
+  // Constructs a file object which doesn't represent any file.
+  file() FMT_NOEXCEPT : fd_(-1) {}
+
+  // Opens a file and constructs a file object representing this file.
+  FMT_API file(cstring_view path, int oflag);
+
+ public:
+  file(const file&) = delete;
+  void operator=(const file&) = delete;
+
+  file(file&& other) FMT_NOEXCEPT : fd_(other.fd_) { other.fd_ = -1; }
+
+  file& operator=(file&& other) FMT_NOEXCEPT {
+    close();
+    fd_ = other.fd_;
+    other.fd_ = -1;
+    return *this;
+  }
+
+  // Destroys the object closing the file it represents if any.
+  FMT_API ~file() FMT_NOEXCEPT;
+
+  // Returns the file descriptor.
+  int descriptor() const FMT_NOEXCEPT { return fd_; }
+
+  // Closes the file.
+  FMT_API void close();
+
+  // Returns the file size. The size has signed type for consistency with
+  // stat::st_size.
+  FMT_API long long size() const;
+
+  // Attempts to read count bytes from the file into the specified buffer.
+  FMT_API size_t read(void* buffer, size_t count);
+
+  // Attempts to write count bytes from the specified buffer to the file.
+  FMT_API size_t write(const void* buffer, size_t count);
+
+  // Duplicates a file descriptor with the dup function and returns
+  // the duplicate as a file object.
+  FMT_API static file dup(int fd);
+
+  // Makes fd be the copy of this file descriptor, closing fd first if
+  // necessary.
+  FMT_API void dup2(int fd);
+
+  // Makes fd be the copy of this file descriptor, closing fd first if
+  // necessary.
+  FMT_API void dup2(int fd, error_code& ec) FMT_NOEXCEPT;
+
+  // Creates a pipe setting up read_end and write_end file objects for reading
+  // and writing respectively.
+  FMT_API static void pipe(file& read_end, file& write_end);
+
+  // Creates a buffered_file object associated with this file and detaches
+  // this file object from the file.
+  FMT_API buffered_file fdopen(const char* mode);
+};
+
+// Returns the memory page size.
+long getpagesize();
+
+namespace detail {
+
+struct buffer_size {
+  size_t value = 0;
+  buffer_size operator=(size_t val) const {
+    auto bs = buffer_size();
+    bs.value = val;
+    return bs;
+  }
+};
+
+struct ostream_params {
+  int oflag = file::WRONLY | file::CREATE;
+  size_t buffer_size = BUFSIZ > 32768 ? BUFSIZ : 32768;
+
+  ostream_params() {}
+
+  template <typename... T>
+  ostream_params(T... params, int oflag) : ostream_params(params...) {
+    this->oflag = oflag;
+  }
+
+  template <typename... T>
+  ostream_params(T... params, detail::buffer_size bs)
+      : ostream_params(params...) {
+    this->buffer_size = bs.value;
+  }
+};
+}  // namespace detail
+
+static constexpr detail::buffer_size buffer_size;
+
+// A fast output stream which is not thread-safe.
+class ostream final : private detail::buffer<char> {
+ private:
+  file file_;
+
+  void flush() {
+    if (size() == 0) return;
+    file_.write(data(), size());
+    clear();
+  }
+
+  FMT_API void grow(size_t) override final;
+
+  ostream(cstring_view path, const detail::ostream_params& params)
+      : file_(path, params.oflag) {
+    set(new char[params.buffer_size], params.buffer_size);
+  }
+
+ public:
+  ostream(ostream&& other)
+      : detail::buffer<char>(other.data(), other.size(), other.capacity()),
+        file_(std::move(other.file_)) {
+    other.set(nullptr, 0);
+  }
+  ~ostream() {
+    flush();
+    delete[] data();
+  }
+
+  template <typename... T>
+  friend ostream output_file(cstring_view path, T... params);
+
+  void close() {
+    flush();
+    file_.close();
+  }
+
+  template <typename S, typename... Args>
+  void print(const S& format_str, const Args&... args) {
+    format_to(detail::buffer_appender<char>(*this), format_str, args...);
+  }
+};
+
+/**
+  Opens a file for writing. Supported parameters passed in `params`:
+  * ``<integer>``: Output flags (``file::WRONLY | file::CREATE`` by default)
+  * ``buffer_size=<integer>``: Output buffer size
+ */
+template <typename... T>
+inline ostream output_file(cstring_view path, T... params) {
+  return {path, detail::ostream_params(params...)};
+}
+#endif  // FMT_USE_FCNTL
+
+#ifdef FMT_LOCALE
+// A "C" numeric locale.
+class locale {
+ private:
+#  ifdef _WIN32
+  using locale_t = _locale_t;
+
+  static void freelocale(locale_t loc) { _free_locale(loc); }
+
+  static double strtod_l(const char* nptr, char** endptr, _locale_t loc) {
+    return _strtod_l(nptr, endptr, loc);
+  }
+#  endif
+
+  locale_t locale_;
+
+ public:
+  using type = locale_t;
+  locale(const locale&) = delete;
+  void operator=(const locale&) = delete;
+
+  locale() {
+#  ifndef _WIN32
+    locale_ = FMT_SYSTEM(newlocale(LC_NUMERIC_MASK, "C", nullptr));
+#  else
+    locale_ = _create_locale(LC_NUMERIC, "C");
+#  endif
+    if (!locale_) FMT_THROW(system_error(errno, "cannot create locale"));
+  }
+  ~locale() { freelocale(locale_); }
+
+  type get() const { return locale_; }
+
+  // Converts string to floating-point number and advances str past the end
+  // of the parsed input.
+  double strtod(const char*& str) const {
+    char* end = nullptr;
+    double result = strtod_l(str, &end, locale_);
+    str = end;
+    return result;
+  }
+};
+using Locale FMT_DEPRECATED_ALIAS = locale;
+#endif  // FMT_LOCALE
+FMT_END_NAMESPACE
+
+#endif  // FMT_OS_H_
diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index 72d078b..29c58ec 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -9,10 +9,15 @@
 #define FMT_OSTREAM_H_
 
 #include <ostream>
+
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+
+template <typename Char> class basic_printf_parse_context;
+template <typename OutputIt, typename Char> class basic_printf_context;
+
+namespace detail {
 
 template <class Char> class formatbuf : public std::basic_streambuf<Char> {
  private:
@@ -44,17 +49,27 @@
   }
 };
 
+struct converter {
+  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)> converter(T);
+};
+
 template <typename Char> struct test_stream : std::basic_ostream<Char> {
  private:
-  // Hide all operator<< from std::basic_ostream<Char>.
-  void_t<> operator<<(null<>);
-  void_t<> operator<<(const Char*);
-
-  template <typename T, FMT_ENABLE_IF(std::is_convertible<T, int>::value &&
-                                      !std::is_enum<T>::value)>
-  void_t<> operator<<(T);
+  void_t<> operator<<(converter);
 };
 
+// Hide insertion operators for built-in types.
+template <typename Char, typename Traits>
+void_t<> operator<<(std::basic_ostream<Char, Traits>&, Char);
+template <typename Char, typename Traits>
+void_t<> operator<<(std::basic_ostream<Char, Traits>&, char);
+template <typename Traits>
+void_t<> operator<<(std::basic_ostream<char, Traits>&, char);
+template <typename Traits>
+void_t<> operator<<(std::basic_ostream<char, Traits>&, signed char);
+template <typename Traits>
+void_t<> operator<<(std::basic_ostream<char, Traits>&, unsigned char);
+
 // Checks if T has a user-defined operator<< (e.g. not a member of
 // std::ostream).
 template <typename T, typename Char> class is_streamable {
@@ -75,7 +90,7 @@
 
 // Write the content of buf to os.
 template <typename Char>
-void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
+void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
   const Char* buf_data = buf.data();
   using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
   unsigned_streamsize size = buf.size();
@@ -93,32 +108,53 @@
                   locale_ref loc = locale_ref()) {
   formatbuf<Char> format_buf(buf);
   std::basic_ostream<Char> output(&format_buf);
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
   if (loc) output.imbue(loc.get<std::locale>());
-  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
+#endif
   output << value;
-  buf.resize(buf.size());
+  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
+  buf.try_resize(buf.size());
 }
 
 // Formats an object of type T that has an overloaded ostream operator<<.
 template <typename T, typename Char>
 struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
-    : formatter<basic_string_view<Char>, Char> {
-  template <typename Context>
-  auto format(const T& value, Context& ctx) -> decltype(ctx.out()) {
+    : private formatter<basic_string_view<Char>, Char> {
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    return formatter<basic_string_view<Char>, Char>::parse(ctx);
+  }
+  template <typename ParseCtx,
+            FMT_ENABLE_IF(std::is_same<
+                          ParseCtx, basic_printf_parse_context<Char>>::value)>
+  auto parse(ParseCtx& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename OutputIt>
+  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx)
+      -> OutputIt {
     basic_memory_buffer<Char> buffer;
     format_value(buffer, value, ctx.locale());
     basic_string_view<Char> str(buffer.data(), buffer.size());
     return formatter<basic_string_view<Char>, Char>::format(str, ctx);
   }
+  template <typename OutputIt>
+  auto format(const T& value, basic_printf_context<OutputIt, Char>& ctx)
+      -> OutputIt {
+    basic_memory_buffer<Char> buffer;
+    format_value(buffer, value, ctx.locale());
+    return std::copy(buffer.begin(), buffer.end(), ctx.out());
+  }
 };
-}  // namespace internal
+}  // namespace detail
 
 template <typename Char>
 void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
-            basic_format_args<buffer_context<Char>> args) {
+            basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  internal::vformat_to(buffer, format_str, args);
-  internal::write(os, buffer);
+  detail::vformat_to(buffer, format_str, args);
+  detail::write_buffer(os, buffer);
 }
 
 /**
@@ -131,10 +167,10 @@
   \endrst
  */
 template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
   vprint(os, to_string_view(format_str),
-         {internal::make_args_checked<Args...>(format_str, args...)});
+         fmt::make_args_checked<Args...>(format_str, args...));
 }
 FMT_END_NAMESPACE
 
diff --git a/include/fmt/posix.h b/include/fmt/posix.h
index e68e226..da19e9d 100644
--- a/include/fmt/posix.h
+++ b/include/fmt/posix.h
@@ -1,321 +1,2 @@
-// A C++ interface to POSIX functions.
-//
-// Copyright (c) 2012 - 2016, Victor Zverovich
-// All rights reserved.
-//
-// For the license information refer to format.h.
-
-#ifndef FMT_POSIX_H_
-#define FMT_POSIX_H_
-
-#if defined(__MINGW32__) || defined(__CYGWIN__)
-// Workaround MinGW bug https://sourceforge.net/p/mingw/bugs/2024/.
-#  undef __STRICT_ANSI__
-#endif
-
-#include <cerrno>
-#include <clocale>  // for locale_t
-#include <cstdio>
-#include <cstdlib>  // for strtod_l
-
-#include <cstddef>
-
-#if defined __APPLE__ || defined(__FreeBSD__)
-#  include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
-#endif
-
-#include "format.h"
-
-// UWP doesn't provide _pipe.
-#if FMT_HAS_INCLUDE("winapifamily.h")
-#  include <winapifamily.h>
-#endif
-#if FMT_HAS_INCLUDE("fcntl.h") && \
-    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
-#  include <fcntl.h>  // for O_RDONLY
-#  define FMT_USE_FCNTL 1
-#else
-#  define FMT_USE_FCNTL 0
-#endif
-
-#ifndef FMT_POSIX
-#  if defined(_WIN32) && !defined(__MINGW32__)
-// Fix warnings about deprecated symbols.
-#    define FMT_POSIX(call) _##call
-#  else
-#    define FMT_POSIX(call) call
-#  endif
-#endif
-
-// Calls to system functions are wrapped in FMT_SYSTEM for testability.
-#ifdef FMT_SYSTEM
-#  define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
-#else
-#  define FMT_SYSTEM(call) call
-#  ifdef _WIN32
-// Fix warnings about deprecated symbols.
-#    define FMT_POSIX_CALL(call) ::_##call
-#  else
-#    define FMT_POSIX_CALL(call) ::call
-#  endif
-#endif
-
-// Retries the expression while it evaluates to error_result and errno
-// equals to EINTR.
-#ifndef _WIN32
-#  define FMT_RETRY_VAL(result, expression, error_result) \
-    do {                                                  \
-      (result) = (expression);                            \
-    } while ((result) == (error_result) && errno == EINTR)
-#else
-#  define FMT_RETRY_VAL(result, expression, error_result) result = (expression)
-#endif
-
-#define FMT_RETRY(result, expression) FMT_RETRY_VAL(result, expression, -1)
-
-FMT_BEGIN_NAMESPACE
-
-/**
-  \rst
-  A reference to a null-terminated string. It can be constructed from a C
-  string or ``std::string``.
-
-  You can use one of the following type aliases for common character types:
-
-  +---------------+-----------------------------+
-  | Type          | Definition                  |
-  +===============+=============================+
-  | cstring_view  | basic_cstring_view<char>    |
-  +---------------+-----------------------------+
-  | wcstring_view | basic_cstring_view<wchar_t> |
-  +---------------+-----------------------------+
-
-  This class is most useful as a parameter type to allow passing
-  different types of strings to a function, for example::
-
-    template <typename... Args>
-    std::string format(cstring_view format_str, const Args & ... args);
-
-    format("{}", 42);
-    format(std::string("{}"), 42);
-  \endrst
- */
-template <typename Char> class basic_cstring_view {
- private:
-  const Char* data_;
-
- public:
-  /** Constructs a string reference object from a C string. */
-  basic_cstring_view(const Char* s) : data_(s) {}
-
-  /**
-    \rst
-    Constructs a string reference from an ``std::string`` object.
-    \endrst
-   */
-  basic_cstring_view(const std::basic_string<Char>& s) : data_(s.c_str()) {}
-
-  /** Returns the pointer to a C string. */
-  const Char* c_str() const { return data_; }
-};
-
-using cstring_view = basic_cstring_view<char>;
-using wcstring_view = basic_cstring_view<wchar_t>;
-
-// An error code.
-class error_code {
- private:
-  int value_;
-
- public:
-  explicit error_code(int value = 0) FMT_NOEXCEPT : value_(value) {}
-
-  int get() const FMT_NOEXCEPT { return value_; }
-};
-
-// A buffered file.
-class buffered_file {
- private:
-  FILE* file_;
-
-  friend class file;
-
-  explicit buffered_file(FILE* f) : file_(f) {}
-
- public:
-  buffered_file(const buffered_file&) = delete;
-  void operator=(const buffered_file&) = delete;
-
-  // Constructs a buffered_file object which doesn't represent any file.
-  buffered_file() FMT_NOEXCEPT : file_(nullptr) {}
-
-  // Destroys the object closing the file it represents if any.
-  FMT_API ~buffered_file() FMT_NOEXCEPT;
-
- public:
-  buffered_file(buffered_file&& other) FMT_NOEXCEPT : file_(other.file_) {
-    other.file_ = nullptr;
-  }
-
-  buffered_file& operator=(buffered_file&& other) {
-    close();
-    file_ = other.file_;
-    other.file_ = nullptr;
-    return *this;
-  }
-
-  // Opens a file.
-  FMT_API buffered_file(cstring_view filename, cstring_view mode);
-
-  // Closes the file.
-  FMT_API void close();
-
-  // Returns the pointer to a FILE object representing this file.
-  FILE* get() const FMT_NOEXCEPT { return file_; }
-
-  // We place parentheses around fileno to workaround a bug in some versions
-  // of MinGW that define fileno as a macro.
-  FMT_API int(fileno)() const;
-
-  void vprint(string_view format_str, format_args args) {
-    fmt::vprint(file_, format_str, args);
-  }
-
-  template <typename... Args>
-  inline void print(string_view format_str, const Args&... args) {
-    vprint(format_str, make_format_args(args...));
-  }
-};
-
-#if FMT_USE_FCNTL
-// A file. Closed file is represented by a file object with descriptor -1.
-// Methods that are not declared with FMT_NOEXCEPT may throw
-// fmt::system_error in case of failure. Note that some errors such as
-// closing the file multiple times will cause a crash on Windows rather
-// than an exception. You can get standard behavior by overriding the
-// invalid parameter handler with _set_invalid_parameter_handler.
-class file {
- private:
-  int fd_;  // File descriptor.
-
-  // Constructs a file object with a given descriptor.
-  explicit file(int fd) : fd_(fd) {}
-
- public:
-  // Possible values for the oflag argument to the constructor.
-  enum {
-    RDONLY = FMT_POSIX(O_RDONLY),  // Open for reading only.
-    WRONLY = FMT_POSIX(O_WRONLY),  // Open for writing only.
-    RDWR = FMT_POSIX(O_RDWR)       // Open for reading and writing.
-  };
-
-  // Constructs a file object which doesn't represent any file.
-  file() FMT_NOEXCEPT : fd_(-1) {}
-
-  // Opens a file and constructs a file object representing this file.
-  FMT_API file(cstring_view path, int oflag);
-
- public:
-  file(const file&) = delete;
-  void operator=(const file&) = delete;
-
-  file(file&& other) FMT_NOEXCEPT : fd_(other.fd_) { other.fd_ = -1; }
-
-  file& operator=(file&& other) FMT_NOEXCEPT {
-    close();
-    fd_ = other.fd_;
-    other.fd_ = -1;
-    return *this;
-  }
-
-  // Destroys the object closing the file it represents if any.
-  FMT_API ~file() FMT_NOEXCEPT;
-
-  // Returns the file descriptor.
-  int descriptor() const FMT_NOEXCEPT { return fd_; }
-
-  // Closes the file.
-  FMT_API void close();
-
-  // Returns the file size. The size has signed type for consistency with
-  // stat::st_size.
-  FMT_API long long size() const;
-
-  // Attempts to read count bytes from the file into the specified buffer.
-  FMT_API std::size_t read(void* buffer, std::size_t count);
-
-  // Attempts to write count bytes from the specified buffer to the file.
-  FMT_API std::size_t write(const void* buffer, std::size_t count);
-
-  // Duplicates a file descriptor with the dup function and returns
-  // the duplicate as a file object.
-  FMT_API static file dup(int fd);
-
-  // Makes fd be the copy of this file descriptor, closing fd first if
-  // necessary.
-  FMT_API void dup2(int fd);
-
-  // Makes fd be the copy of this file descriptor, closing fd first if
-  // necessary.
-  FMT_API void dup2(int fd, error_code& ec) FMT_NOEXCEPT;
-
-  // Creates a pipe setting up read_end and write_end file objects for reading
-  // and writing respectively.
-  FMT_API static void pipe(file& read_end, file& write_end);
-
-  // Creates a buffered_file object associated with this file and detaches
-  // this file object from the file.
-  FMT_API buffered_file fdopen(const char* mode);
-};
-
-// Returns the memory page size.
-long getpagesize();
-#endif  // FMT_USE_FCNTL
-
-#ifdef FMT_LOCALE
-// A "C" numeric locale.
-class Locale {
- private:
-#  ifdef _WIN32
-  using locale_t = _locale_t;
-
-  enum { LC_NUMERIC_MASK = LC_NUMERIC };
-
-  static locale_t newlocale(int category_mask, const char* locale, locale_t) {
-    return _create_locale(category_mask, locale);
-  }
-
-  static void freelocale(locale_t locale) { _free_locale(locale); }
-
-  static double strtod_l(const char* nptr, char** endptr, _locale_t locale) {
-    return _strtod_l(nptr, endptr, locale);
-  }
-#  endif
-
-  locale_t locale_;
-
- public:
-  using type = locale_t;
-  Locale(const Locale&) = delete;
-  void operator=(const Locale&) = delete;
-
-  Locale() : locale_(newlocale(LC_NUMERIC_MASK, "C", nullptr)) {
-    if (!locale_) FMT_THROW(system_error(errno, "cannot create locale"));
-  }
-  ~Locale() { freelocale(locale_); }
-
-  type get() const { return locale_; }
-
-  // Converts string to floating-point number and advances str past the end
-  // of the parsed input.
-  double strtod(const char*& str) const {
-    char* end = nullptr;
-    double result = strtod_l(str, &end, locale_);
-    str = end;
-    return result;
-  }
-};
-#endif  // FMT_LOCALE
-FMT_END_NAMESPACE
-
-#endif  // FMT_POSIX_H_
+#include "os.h"
+#warning "fmt/posix.h is deprecated; use fmt/os.h instead"
diff --git a/include/fmt/printf.h b/include/fmt/printf.h
index cdbb65e..8c28ac2 100644
--- a/include/fmt/printf.h
+++ b/include/fmt/printf.h
@@ -14,7 +14,7 @@
 #include "ostream.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
@@ -28,7 +28,7 @@
 
 template <> struct int_checker<true> {
   template <typename T> static bool fits_in_int(T value) {
-    return value >= std::numeric_limits<int>::min() &&
+    return value >= (std::numeric_limits<int>::min)() &&
            value <= max_value<int>();
   }
   static bool fits_in_int(int) { return true; }
@@ -90,11 +90,11 @@
     if (const_check(sizeof(target_type) <= sizeof(int))) {
       // Extra casts are used to silence warnings.
       if (is_signed) {
-        arg_ = internal::make_arg<Context>(
+        arg_ = detail::make_arg<Context>(
             static_cast<int>(static_cast<target_type>(value)));
       } else {
         using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
-        arg_ = internal::make_arg<Context>(
+        arg_ = detail::make_arg<Context>(
             static_cast<unsigned>(static_cast<unsigned_type>(value)));
       }
     } else {
@@ -102,9 +102,9 @@
         // glibc's printf doesn't sign extend arguments of smaller types:
         //   std::printf("%lld", -42);  // prints "4294967254"
         // but we don't have to do the same because it's a UB.
-        arg_ = internal::make_arg<Context>(static_cast<long long>(value));
+        arg_ = detail::make_arg<Context>(static_cast<long long>(value));
       } else {
-        arg_ = internal::make_arg<Context>(
+        arg_ = detail::make_arg<Context>(
             static_cast<typename make_unsigned_or_bool<U>::type>(value));
       }
     }
@@ -133,7 +133,7 @@
 
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   void operator()(T value) {
-    arg_ = internal::make_arg<Context>(
+    arg_ = detail::make_arg<Context>(
         static_cast<typename Context::char_type>(value));
   }
 
@@ -141,6 +141,13 @@
   void operator()(T) {}  // No conversion needed for non-integral types.
 };
 
+// An argument visitor that return a pointer to a C string if argument is a
+// string or null otherwise.
+template <typename Char> struct get_cstring {
+  template <typename T> const Char* operator()(T) { return nullptr; }
+  const Char* operator()(const Char* s) { return s; }
+};
+
 // Checks if an argument is a valid printf width specifier and sets
 // left alignment if it is negative.
 template <typename Char> class printf_width_handler {
@@ -155,7 +162,7 @@
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   unsigned operator()(T value) {
     auto width = static_cast<uint32_or_64_or_128_t<T>>(value);
-    if (internal::is_negative(value)) {
+    if (detail::is_negative(value)) {
       specs_.align = align::left;
       width = 0 - width;
     }
@@ -172,23 +179,25 @@
 };
 
 template <typename Char, typename Context>
-void printf(buffer<Char>& buf, basic_string_view<Char> format,
-            basic_format_args<Context> args) {
-  Context(std::back_inserter(buf), format, args).format();
+void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
+             basic_format_args<Context> args) {
+  Context(buffer_appender<Char>(buf), format, args).format();
 }
+}  // namespace detail
 
-template <typename OutputIt, typename Char, typename Context>
-internal::truncating_iterator<OutputIt> printf(
-    internal::truncating_iterator<OutputIt> it, basic_string_view<Char> format,
-    basic_format_args<Context> args) {
-  return Context(it, format, args).format();
+// For printing into memory_buffer.
+template <typename Char, typename Context>
+FMT_DEPRECATED void printf(detail::buffer<Char>& buf,
+                           basic_string_view<Char> format,
+                           basic_format_args<Context> args) {
+  return detail::vprintf(buf, format, args);
 }
-}  // namespace internal
+using detail::vprintf;
 
-using internal::printf;  // For printing into memory_buffer.
-
-template <typename Range> class printf_arg_formatter;
-
+template <typename Char>
+class basic_printf_parse_context : public basic_format_parse_context<Char> {
+  using basic_format_parse_context<Char>::basic_format_parse_context;
+};
 template <typename OutputIt, typename Char> class basic_printf_context;
 
 /**
@@ -196,15 +205,15 @@
   The ``printf`` argument formatter.
   \endrst
  */
-template <typename Range>
-class printf_arg_formatter : public internal::arg_formatter_base<Range> {
+template <typename OutputIt, typename Char>
+class printf_arg_formatter : public detail::arg_formatter_base<OutputIt, Char> {
  public:
-  using iterator = typename Range::iterator;
+  using iterator = OutputIt;
 
  private:
-  using char_type = typename Range::value_type;
-  using base = internal::arg_formatter_base<Range>;
-  using context_type = basic_printf_context<iterator, char_type>;
+  using char_type = Char;
+  using base = detail::arg_formatter_base<OutputIt, Char>;
+  using context_type = basic_printf_context<OutputIt, Char>;
 
   context_type& context_;
 
@@ -229,9 +238,9 @@
     \endrst
    */
   printf_arg_formatter(iterator iter, format_specs& specs, context_type& ctx)
-      : base(Range(iter), &specs, internal::locale_ref()), context_(ctx) {}
+      : base(iter, &specs, detail::locale_ref()), context_(ctx) {}
 
-  template <typename T, FMT_ENABLE_IF(fmt::internal::is_integral<T>::value)>
+  template <typename T, FMT_ENABLE_IF(fmt::detail::is_integral<T>::value)>
   iterator operator()(T value) {
     // MSVC2013 fails to compile separate overloads for bool and char_type so
     // use std::is_same instead.
@@ -246,7 +255,11 @@
         return (*this)(static_cast<int>(value));
       fmt_specs.sign = sign::none;
       fmt_specs.alt = false;
-      fmt_specs.align = align::right;
+      fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
+      // align::numeric needs to be overwritten here since the '0' flag is
+      // ignored for non-numeric types
+      if (fmt_specs.align == align::none || fmt_specs.align == align::numeric)
+        fmt_specs.align = align::right;
       return base::operator()(value);
     } else {
       return base::operator()(value);
@@ -303,6 +316,8 @@
 };
 
 template <typename T> struct printf_formatter {
+  printf_formatter() = delete;
+
   template <typename ParseContext>
   auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
     return ctx.begin();
@@ -310,17 +325,21 @@
 
   template <typename FormatContext>
   auto format(const T& value, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::format_value(internal::get_container(ctx.out()), value);
+    detail::format_value(detail::get_container(ctx.out()), value);
     return ctx.out();
   }
 };
 
-/** This template formats data and writes the output to a writer. */
+/**
+ This template formats data and writes the output through an output iterator.
+ */
 template <typename OutputIt, typename Char> class basic_printf_context {
  public:
   /** The character type for the output. */
   using char_type = Char;
+  using iterator = OutputIt;
   using format_arg = basic_format_arg<basic_printf_context>;
+  using parse_context_type = basic_printf_parse_context<Char>;
   template <typename T> using formatter_type = printf_formatter<T>;
 
  private:
@@ -328,24 +347,23 @@
 
   OutputIt out_;
   basic_format_args<basic_printf_context> args_;
-  basic_format_parse_context<Char> parse_ctx_;
+  parse_context_type parse_ctx_;
 
   static void parse_flags(format_specs& specs, const Char*& it,
                           const Char* end);
 
-  // Returns the argument with specified index or, if arg_index is equal
-  // to the maximum unsigned value, the next argument.
-  format_arg get_arg(unsigned arg_index = internal::max_value<unsigned>());
+  // Returns the argument with specified index or, if arg_index is -1, the next
+  // argument.
+  format_arg get_arg(int arg_index = -1);
 
   // Parses argument index, flags and width and returns the argument index.
-  unsigned parse_header(const Char*& it, const Char* end, format_specs& specs);
+  int parse_header(const Char*& it, const Char* end, format_specs& specs);
 
  public:
   /**
    \rst
-   Constructs a ``printf_context`` object. References to the arguments and
-   the writer are stored in the context object so make sure they have
-   appropriate lifetimes.
+   Constructs a ``printf_context`` object. References to the arguments are
+   stored in the context object so make sure they have appropriate lifetimes.
    \endrst
    */
   basic_printf_context(OutputIt out, basic_string_view<char_type> format_str,
@@ -355,16 +373,18 @@
   OutputIt out() { return out_; }
   void advance_to(OutputIt it) { out_ = it; }
 
-  format_arg arg(unsigned id) const { return args_.get(id); }
+  detail::locale_ref locale() { return {}; }
 
-  basic_format_parse_context<Char>& parse_context() { return parse_ctx_; }
+  format_arg arg(int id) const { return args_.get(id); }
+
+  parse_context_type& parse_context() { return parse_ctx_; }
 
   FMT_CONSTEXPR void on_error(const char* message) {
     parse_ctx_.on_error(message);
   }
 
   /** Formats stored arguments and writes the output to the range. */
-  template <typename ArgFormatter = printf_arg_formatter<buffer_range<Char>>>
+  template <typename ArgFormatter = printf_arg_formatter<OutputIt, Char>>
   OutputIt format();
 };
 
@@ -384,7 +404,9 @@
       specs.fill[0] = '0';
       break;
     case ' ':
-      specs.sign = sign::space;
+      if (specs.sign != sign::plus) {
+        specs.sign = sign::space;
+      }
       break;
     case '#':
       specs.alt = true;
@@ -397,24 +419,25 @@
 
 template <typename OutputIt, typename Char>
 typename basic_printf_context<OutputIt, Char>::format_arg
-basic_printf_context<OutputIt, Char>::get_arg(unsigned arg_index) {
-  if (arg_index == internal::max_value<unsigned>())
+basic_printf_context<OutputIt, Char>::get_arg(int arg_index) {
+  if (arg_index < 0)
     arg_index = parse_ctx_.next_arg_id();
   else
     parse_ctx_.check_arg_id(--arg_index);
-  return internal::get_arg(*this, arg_index);
+  return detail::get_arg(*this, arg_index);
 }
 
 template <typename OutputIt, typename Char>
-unsigned basic_printf_context<OutputIt, Char>::parse_header(
-    const Char*& it, const Char* end, format_specs& specs) {
-  unsigned arg_index = internal::max_value<unsigned>();
+int basic_printf_context<OutputIt, Char>::parse_header(const Char*& it,
+                                                       const Char* end,
+                                                       format_specs& specs) {
+  int arg_index = -1;
   char_type c = *it;
   if (c >= '0' && c <= '9') {
     // Parse an argument index (if followed by '$') or a width possibly
     // preceded with '0' flag(s).
-    internal::error_handler eh;
-    unsigned value = parse_nonnegative_int(it, end, eh);
+    detail::error_handler eh;
+    int value = parse_nonnegative_int(it, end, eh);
     if (it != end && *it == '$') {  // value is an argument index
       ++it;
       arg_index = value;
@@ -432,12 +455,12 @@
   // Parse width.
   if (it != end) {
     if (*it >= '0' && *it <= '9') {
-      internal::error_handler eh;
+      detail::error_handler eh;
       specs.width = parse_nonnegative_int(it, end, eh);
     } else if (*it == '*') {
       ++it;
-      specs.width = visit_format_arg(
-          internal::printf_width_handler<char_type>(specs), get_arg());
+      specs.width = static_cast<int>(visit_format_arg(
+          detail::printf_width_handler<char_type>(specs), get_arg()));
     }
   }
   return arg_index;
@@ -464,39 +487,53 @@
     specs.align = align::right;
 
     // Parse argument index, flags and width.
-    unsigned arg_index = parse_header(it, end, specs);
-    if (arg_index == 0) on_error("argument index out of range");
+    int arg_index = parse_header(it, end, specs);
+    if (arg_index == 0) on_error("argument not found");
 
     // Parse precision.
     if (it != end && *it == '.') {
       ++it;
       c = it != end ? *it : 0;
       if ('0' <= c && c <= '9') {
-        internal::error_handler eh;
-        specs.precision = static_cast<int>(parse_nonnegative_int(it, end, eh));
+        detail::error_handler eh;
+        specs.precision = parse_nonnegative_int(it, end, eh);
       } else if (c == '*') {
         ++it;
-        specs.precision =
-            visit_format_arg(internal::printf_precision_handler(), get_arg());
+        specs.precision = static_cast<int>(
+            visit_format_arg(detail::printf_precision_handler(), get_arg()));
       } else {
         specs.precision = 0;
       }
     }
 
     format_arg arg = get_arg(arg_index);
-    if (specs.alt && visit_format_arg(internal::is_zero_int(), arg))
+    // For d, i, o, u, x, and X conversion specifiers, if a precision is
+    // specified, the '0' flag is ignored
+    if (specs.precision >= 0 && arg.is_integral())
+      specs.fill[0] =
+          ' ';  // Ignore '0' flag for non-numeric types or if '-' present.
+    if (specs.precision >= 0 && arg.type() == detail::type::cstring_type) {
+      auto str = visit_format_arg(detail::get_cstring<Char>(), arg);
+      auto str_end = str + specs.precision;
+      auto nul = std::find(str, str_end, Char());
+      arg = detail::make_arg<basic_printf_context>(basic_string_view<Char>(
+          str,
+          detail::to_unsigned(nul != str_end ? nul - str : specs.precision)));
+    }
+    if (specs.alt && visit_format_arg(detail::is_zero_int(), arg))
       specs.alt = false;
     if (specs.fill[0] == '0') {
-      if (arg.is_arithmetic())
+      if (arg.is_arithmetic() && specs.align != align::left)
         specs.align = align::numeric;
       else
-        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types.
+        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types or if '-'
+                              // flag is also present.
     }
 
     // Parse length and convert the argument to the required type.
     c = it != end ? *it++ : 0;
     char_type t = it != end ? *it : 0;
-    using internal::convert_arg;
+    using detail::convert_arg;
     switch (c) {
     case 'h':
       if (t == 'h') {
@@ -520,7 +557,7 @@
       convert_arg<intmax_t>(arg, t);
       break;
     case 'z':
-      convert_arg<std::size_t>(arg, t);
+      convert_arg<size_t>(arg, t);
       break;
     case 't':
       convert_arg<std::ptrdiff_t>(arg, t);
@@ -545,7 +582,7 @@
         specs.type = 'd';
         break;
       case 'c':
-        visit_format_arg(internal::char_converter<basic_printf_context>(arg),
+        visit_format_arg(detail::char_converter<basic_printf_context>(arg),
                          arg);
         break;
       }
@@ -554,15 +591,14 @@
     start = it;
 
     // Format argument.
-    visit_format_arg(ArgFormatter(out, specs, *this), arg);
+    out = visit_format_arg(ArgFormatter(out, specs, *this), arg);
   }
   return std::copy(start, it, out);
 }
 
 template <typename Char>
 using basic_printf_context_t =
-    basic_printf_context<std::back_insert_iterator<internal::buffer<Char>>,
-                         Char>;
+    basic_printf_context<detail::buffer_appender<Char>, Char>;
 
 using printf_context = basic_printf_context_t<char>;
 using wprintf_context = basic_printf_context_t<wchar_t>;
@@ -596,9 +632,10 @@
 
 template <typename S, typename Char = char_t<S>>
 inline std::basic_string<Char> vsprintf(
-    const S& format, basic_format_args<basic_printf_context_t<Char>> args) {
+    const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
+  vprintf(buffer, to_string_view(format), args);
   return to_string(buffer);
 }
 
@@ -612,18 +649,19 @@
   \endrst
 */
 template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline std::basic_string<Char> sprintf(const S& format, const Args&... args) {
   using context = basic_printf_context_t<Char>;
-  return vsprintf(to_string_view(format), {make_format_args<context>(args...)});
+  return vsprintf(to_string_view(format), make_format_args<context>(args...));
 }
 
 template <typename S, typename Char = char_t<S>>
-inline int vfprintf(std::FILE* f, const S& format,
-                    basic_format_args<basic_printf_context_t<Char>> args) {
+inline int vfprintf(
+    std::FILE* f, const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  std::size_t size = buffer.size();
+  vprintf(buffer, to_string_view(format), args);
+  size_t size = buffer.size();
   return std::fwrite(buffer.data(), sizeof(Char), size, f) < size
              ? -1
              : static_cast<int>(size);
@@ -639,16 +677,17 @@
   \endrst
  */
 template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline int fprintf(std::FILE* f, const S& format, const Args&... args) {
   using context = basic_printf_context_t<Char>;
   return vfprintf(f, to_string_view(format),
-                  {make_format_args<context>(args...)});
+                  make_format_args<context>(args...));
 }
 
 template <typename S, typename Char = char_t<S>>
-inline int vprintf(const S& format,
-                   basic_format_args<basic_printf_context_t<Char>> args) {
+inline int vprintf(
+    const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   return vfprintf(stdout, to_string_view(format), args);
 }
 
@@ -662,19 +701,20 @@
   \endrst
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 inline int printf(const S& format_str, const Args&... args) {
   using context = basic_printf_context_t<char_t<S>>;
   return vprintf(to_string_view(format_str),
-                 {make_format_args<context>(args...)});
+                 make_format_args<context>(args...));
 }
 
 template <typename S, typename Char = char_t<S>>
-inline int vfprintf(std::basic_ostream<Char>& os, const S& format,
-                    basic_format_args<basic_printf_context_t<Char>> args) {
+inline int vfprintf(
+    std::basic_ostream<Char>& os, const S& format,
+    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  internal::write(os, buffer);
+  vprintf(buffer, to_string_view(format), args);
+  detail::write_buffer(os, buffer);
   return static_cast<int>(buffer.size());
 }
 
@@ -682,9 +722,9 @@
 template <typename ArgFormatter, typename Char,
           typename Context =
               basic_printf_context<typename ArgFormatter::iterator, Char>>
-typename ArgFormatter::iterator vprintf(internal::buffer<Char>& out,
-                                        basic_string_view<Char> format_str,
-                                        basic_format_args<Context> args) {
+typename ArgFormatter::iterator vprintf(
+    detail::buffer<Char>& out, basic_string_view<Char> format_str,
+    basic_format_args<type_identity_t<Context>> args) {
   typename ArgFormatter::iterator iter(out);
   Context(iter, format_str, args).template format<ArgFormatter>();
   return iter;
@@ -704,7 +744,7 @@
                    const Args&... args) {
   using context = basic_printf_context_t<Char>;
   return vfprintf(os, to_string_view(format_str),
-                  {make_format_args<context>(args...)});
+                  make_format_args<context>(args...));
 }
 FMT_END_NAMESPACE
 
diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index 6110fda..632f049 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -12,7 +12,9 @@
 #ifndef FMT_RANGES_H_
 #define FMT_RANGES_H_
 
+#include <initializer_list>
 #include <type_traits>
+
 #include "format.h"
 
 // output only up to N items from the range.
@@ -31,7 +33,7 @@
 
 template <typename Char, typename Enable = void>
 struct formatting_range : formatting_base<Char> {
-  static FMT_CONSTEXPR_DECL const std::size_t range_length_limit =
+  static FMT_CONSTEXPR_DECL const size_t range_length_limit =
       FMT_RANGE_OUTPUT_LENGTH_LIMIT;  // output only up to N items from the
                                       // range.
   Char prefix;
@@ -52,7 +54,7 @@
   static FMT_CONSTEXPR_DECL const bool add_prepostfix_space = false;
 };
 
-namespace internal {
+namespace detail {
 
 template <typename RangeT, typename OutputIterator>
 OutputIterator copy(const RangeT& range, OutputIterator out) {
@@ -104,10 +106,7 @@
 /// tuple_size and tuple_element check.
 template <typename T> class is_tuple_like_ {
   template <typename U>
-  static auto check(U* p)
-      -> decltype(std::tuple_size<U>::value,
-                  (void)std::declval<typename std::tuple_element<0, U>::type>(),
-                  int());
+  static auto check(U* p) -> decltype(std::tuple_size<U>::value, int());
   template <typename> static void check(...);
 
  public:
@@ -119,26 +118,24 @@
 #if defined(__cpp_lib_integer_sequence) || FMT_MSC_VER >= 1900
 template <typename T, T... N>
 using integer_sequence = std::integer_sequence<T, N...>;
-template <std::size_t... N> using index_sequence = std::index_sequence<N...>;
-template <std::size_t N>
-using make_index_sequence = std::make_index_sequence<N>;
+template <size_t... N> using index_sequence = std::index_sequence<N...>;
+template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
 #else
 template <typename T, T... N> struct integer_sequence {
   using value_type = T;
 
-  static FMT_CONSTEXPR std::size_t size() { return sizeof...(N); }
+  static FMT_CONSTEXPR size_t size() { return sizeof...(N); }
 };
 
-template <std::size_t... N>
-using index_sequence = integer_sequence<std::size_t, N...>;
+template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
 
-template <typename T, std::size_t N, T... Ns>
+template <typename T, size_t N, T... Ns>
 struct make_integer_sequence : make_integer_sequence<T, N - 1, N - 1, Ns...> {};
 template <typename T, T... Ns>
 struct make_integer_sequence<T, 0, Ns...> : integer_sequence<T, Ns...> {};
 
-template <std::size_t N>
-using make_index_sequence = make_integer_sequence<std::size_t, N>;
+template <size_t N>
+using make_index_sequence = make_integer_sequence<size_t, N>;
 #endif
 
 template <class Tuple, class F, size_t... Is>
@@ -160,6 +157,9 @@
   for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
 }
 
+template <typename Range>
+using value_type = remove_cvref_t<decltype(*std::declval<Range>().begin())>;
+
 template <typename Arg, FMT_ENABLE_IF(!is_like_std_string<
                                       typename std::decay<Arg>::type>::value)>
 FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&) {
@@ -185,12 +185,11 @@
 FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t) {
   return add_space ? L" '{}'" : L"'{}'";
 }
-
-}  // namespace internal
+}  // namespace detail
 
 template <typename T> struct is_tuple_like {
   static FMT_CONSTEXPR_DECL const bool value =
-      internal::is_tuple_like_<T>::value && !internal::is_range_<T>::value;
+      detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
 };
 
 template <typename TupleT, typename Char>
@@ -203,17 +202,17 @@
         if (formatting.add_prepostfix_space) {
           *out++ = ' ';
         }
-        out = internal::copy(formatting.delimiter, out);
+        out = detail::copy(formatting.delimiter, out);
       }
       out = format_to(out,
-                      internal::format_str_quoted(
+                      detail::format_str_quoted(
                           (formatting.add_delimiter_spaces && i > 0), v),
                       v);
       ++i;
     }
 
     formatting_tuple<Char>& formatting;
-    std::size_t& i;
+    size_t& i;
     typename std::add_lvalue_reference<decltype(
         std::declval<FormatContext>().out())>::type out;
   };
@@ -229,14 +228,14 @@
   template <typename FormatContext = format_context>
   auto format(const TupleT& values, FormatContext& ctx) -> decltype(ctx.out()) {
     auto out = ctx.out();
-    std::size_t i = 0;
-    internal::copy(formatting.prefix, out);
+    size_t i = 0;
+    detail::copy(formatting.prefix, out);
 
-    internal::for_each(values, format_each<FormatContext>{formatting, i, out});
+    detail::for_each(values, format_each<FormatContext>{formatting, i, out});
     if (formatting.add_prepostfix_space) {
       *out++ = ' ';
     }
-    internal::copy(formatting.postfix, out);
+    detail::copy(formatting.postfix, out);
 
     return ctx.out();
   }
@@ -244,15 +243,23 @@
 
 template <typename T, typename Char> struct is_range {
   static FMT_CONSTEXPR_DECL const bool value =
-      internal::is_range_<T>::value &&
-      !internal::is_like_std_string<T>::value &&
+      detail::is_range_<T>::value && !detail::is_like_std_string<T>::value &&
       !std::is_convertible<T, std::basic_string<Char>>::value &&
-      !std::is_constructible<internal::std_string_view<Char>, T>::value;
+      !std::is_constructible<detail::std_string_view<Char>, T>::value;
 };
 
-template <typename RangeT, typename Char>
-struct formatter<RangeT, Char,
-                 enable_if_t<fmt::is_range<RangeT, Char>::value>> {
+template <typename T, typename Char>
+struct formatter<
+    T, Char,
+    enable_if_t<fmt::is_range<T, Char>::value
+// Workaround a bug in MSVC 2017 and earlier.
+#if !FMT_MSC_VER || FMT_MSC_VER >= 1927
+                &&
+                (has_formatter<detail::value_type<T>, format_context>::value ||
+                 detail::has_fallback_formatter<detail::value_type<T>,
+                                                format_context>::value)
+#endif
+                >> {
   formatting_range<Char> formatting;
 
   template <typename ParseContext>
@@ -261,17 +268,18 @@
   }
 
   template <typename FormatContext>
-  typename FormatContext::iterator format(const RangeT& values,
-                                          FormatContext& ctx) {
-    auto out = internal::copy(formatting.prefix, ctx.out());
-    std::size_t i = 0;
-    for (auto it = values.begin(), end = values.end(); it != end; ++it) {
+  typename FormatContext::iterator format(const T& values, FormatContext& ctx) {
+    auto out = detail::copy(formatting.prefix, ctx.out());
+    size_t i = 0;
+    auto it = values.begin();
+    auto end = values.end();
+    for (; it != end; ++it) {
       if (i > 0) {
         if (formatting.add_prepostfix_space) *out++ = ' ';
-        out = internal::copy(formatting.delimiter, out);
+        out = detail::copy(formatting.delimiter, out);
       }
       out = format_to(out,
-                      internal::format_str_quoted(
+                      detail::format_str_quoted(
                           (formatting.add_delimiter_spaces && i > 0), *it),
                       *it);
       if (++i > formatting.range_length_limit) {
@@ -280,11 +288,11 @@
       }
     }
     if (formatting.add_prepostfix_space) *out++ = ' ';
-    return internal::copy(formatting.postfix, out);
+    return detail::copy(formatting.postfix, out);
   }
 };
 
-template <typename Char, typename... T> struct tuple_arg_join : internal::view {
+template <typename Char, typename... T> struct tuple_arg_join : detail::view {
   const std::tuple<T...>& tuple;
   basic_string_view<Char> sep;
 
@@ -302,14 +310,14 @@
   template <typename FormatContext>
   typename FormatContext::iterator format(
       const tuple_arg_join<Char, T...>& value, FormatContext& ctx) {
-    return format(value, ctx, internal::make_index_sequence<sizeof...(T)>{});
+    return format(value, ctx, detail::make_index_sequence<sizeof...(T)>{});
   }
 
  private:
   template <typename FormatContext, size_t... N>
   typename FormatContext::iterator format(
       const tuple_arg_join<Char, T...>& value, FormatContext& ctx,
-      internal::index_sequence<N...>) {
+      detail::index_sequence<N...>) {
     return format_args(value, ctx, std::get<N>(value.tuple)...);
   }
 
@@ -360,6 +368,29 @@
   return {tuple, sep};
 }
 
+/**
+  \rst
+  Returns an object that formats `initializer_list` with elements separated by
+  `sep`.
+
+  **Example**::
+
+    fmt::print("{}", fmt::join({1, 2, 3}, ", "));
+    // Output: "1, 2, 3"
+  \endrst
+ */
+template <typename T>
+arg_join<const T*, const T*, char> join(std::initializer_list<T> list,
+                                        string_view sep) {
+  return join(std::begin(list), std::end(list), sep);
+}
+
+template <typename T>
+arg_join<const T*, const T*, wchar_t> join(std::initializer_list<T> list,
+                                           wstring_view sep) {
+  return join(std::begin(list), std::end(list), sep);
+}
+
 FMT_END_NAMESPACE
 
 #endif  // FMT_RANGES_H_
diff --git a/.github/pull_request_template.md b/pull_request_template.md
similarity index 100%
rename from .github/pull_request_template.md
rename to pull_request_template.md
diff --git a/src/format.cc b/src/format.cc
index c373db1..6141d96 100644
--- a/src/format.cc
+++ b/src/format.cc
@@ -8,56 +8,92 @@
 #include "fmt/format-inl.h"
 
 FMT_BEGIN_NAMESPACE
-template struct FMT_API internal::basic_data<void>;
+namespace detail {
+
+template <typename T>
+int format_float(char* buf, std::size_t size, const char* format, int precision,
+                 T value) {
+#ifdef FMT_FUZZ
+  if (precision > 100000)
+    throw std::runtime_error(
+        "fuzz mode - avoid large allocation inside snprintf");
+#endif
+  // Suppress the warning about nonliteral format string.
+  int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
+  return precision < 0 ? snprintf_ptr(buf, size, format, value)
+                       : snprintf_ptr(buf, size, format, precision, value);
+}
+
+template FMT_API dragonbox::decimal_fp<float> dragonbox::to_decimal(float x)
+    FMT_NOEXCEPT;
+template FMT_API dragonbox::decimal_fp<double> dragonbox::to_decimal(double x)
+    FMT_NOEXCEPT;
+
+// DEPRECATED! This function exists for ABI compatibility.
+template <typename Char>
+typename basic_format_context<std::back_insert_iterator<buffer<Char>>,
+                              Char>::iterator
+vformat_to(buffer<Char>& buf, basic_string_view<Char> format_str,
+           basic_format_args<basic_format_context<
+               std::back_insert_iterator<buffer<type_identity_t<Char>>>,
+               type_identity_t<Char>>>
+               args) {
+  using iterator = std::back_insert_iterator<buffer<char>>;
+  using context = basic_format_context<
+      std::back_insert_iterator<buffer<type_identity_t<Char>>>,
+      type_identity_t<Char>>;
+  auto out = iterator(buf);
+  format_handler<iterator, Char, context> h(out, format_str, args, {});
+  parse_format_string<false>(format_str, h);
+  return out;
+}
+template basic_format_context<std::back_insert_iterator<buffer<char>>,
+                              char>::iterator
+vformat_to(buffer<char>&, string_view,
+           basic_format_args<basic_format_context<
+               std::back_insert_iterator<buffer<type_identity_t<char>>>,
+               type_identity_t<char>>>);
+}  // namespace detail
+
+template struct FMT_INSTANTIATION_DEF_API detail::basic_data<void>;
 
 // Workaround a bug in MSVC2013 that prevents instantiation of format_float.
-int (*instantiate_format_float)(double, int, internal::float_specs,
-                                internal::buffer<char>&) =
-    internal::format_float;
+int (*instantiate_format_float)(double, int, detail::float_specs,
+                                detail::buffer<char>&) = detail::format_float;
 
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
-template FMT_API internal::locale_ref::locale_ref(const std::locale& loc);
-template FMT_API std::locale internal::locale_ref::get<std::locale>() const;
+template FMT_API detail::locale_ref::locale_ref(const std::locale& loc);
+template FMT_API std::locale detail::locale_ref::get<std::locale>() const;
 #endif
 
 // Explicit instantiations for char.
 
-template FMT_API std::string internal::grouping_impl<char>(locale_ref);
-template FMT_API char internal::thousands_sep_impl(locale_ref);
-template FMT_API char internal::decimal_point_impl(locale_ref);
+template FMT_API std::string detail::grouping_impl<char>(locale_ref);
+template FMT_API char detail::thousands_sep_impl(locale_ref);
+template FMT_API char detail::decimal_point_impl(locale_ref);
 
-template FMT_API void internal::buffer<char>::append(const char*, const char*);
+template FMT_API void detail::buffer<char>::append(const char*, const char*);
 
-template FMT_API void internal::arg_map<format_context>::init(
-    const basic_format_args<format_context>& args);
+template FMT_API void detail::vformat_to(
+    detail::buffer<char>&, string_view,
+    basic_format_args<FMT_BUFFER_CONTEXT(char)>, detail::locale_ref);
 
-template FMT_API std::string internal::vformat<char>(
-    string_view, basic_format_args<format_context>);
-
-template FMT_API format_context::iterator internal::vformat_to(
-    internal::buffer<char>&, string_view, basic_format_args<format_context>);
-
-template FMT_API int internal::snprintf_float(double, int,
-                                              internal::float_specs,
-                                              internal::buffer<char>&);
-template FMT_API int internal::snprintf_float(long double, int,
-                                              internal::float_specs,
-                                              internal::buffer<char>&);
-template FMT_API int internal::format_float(double, int, internal::float_specs,
-                                            internal::buffer<char>&);
-template FMT_API int internal::format_float(long double, int,
-                                            internal::float_specs,
-                                            internal::buffer<char>&);
+template FMT_API int detail::snprintf_float(double, int, detail::float_specs,
+                                            detail::buffer<char>&);
+template FMT_API int detail::snprintf_float(long double, int,
+                                            detail::float_specs,
+                                            detail::buffer<char>&);
+template FMT_API int detail::format_float(double, int, detail::float_specs,
+                                          detail::buffer<char>&);
+template FMT_API int detail::format_float(long double, int, detail::float_specs,
+                                          detail::buffer<char>&);
 
 // Explicit instantiations for wchar_t.
 
-template FMT_API std::string internal::grouping_impl<wchar_t>(locale_ref);
-template FMT_API wchar_t internal::thousands_sep_impl(locale_ref);
-template FMT_API wchar_t internal::decimal_point_impl(locale_ref);
+template FMT_API std::string detail::grouping_impl<wchar_t>(locale_ref);
+template FMT_API wchar_t detail::thousands_sep_impl(locale_ref);
+template FMT_API wchar_t detail::decimal_point_impl(locale_ref);
 
-template FMT_API void internal::buffer<wchar_t>::append(const wchar_t*,
-                                                        const wchar_t*);
-
-template FMT_API std::wstring internal::vformat<wchar_t>(
-    wstring_view, basic_format_args<wformat_context>);
+template FMT_API void detail::buffer<wchar_t>::append(const wchar_t*,
+                                                      const wchar_t*);
 FMT_END_NAMESPACE
diff --git a/src/posix.cc b/src/os.cc
similarity index 63%
rename from src/posix.cc
rename to src/os.cc
index 3db72b7..6850024 100644
--- a/src/posix.cc
+++ b/src/os.cc
@@ -1,4 +1,4 @@
-// A C++ interface to POSIX functions.
+// Formatting library for C++ - optional OS-specific functionality
 //
 // Copyright (c) 2012 - 2016, Victor Zverovich
 // All rights reserved.
@@ -10,39 +10,43 @@
 #  define _CRT_SECURE_NO_WARNINGS
 #endif
 
-#include "fmt/posix.h"
+#include "fmt/os.h"
 
 #include <climits>
 
 #if FMT_USE_FCNTL
-#include <sys/stat.h>
-#include <sys/types.h>
+#  include <sys/stat.h>
+#  include <sys/types.h>
 
-#ifndef _WIN32
-#  include <unistd.h>
-#else
-#  ifndef WIN32_LEAN_AND_MEAN
-#    define WIN32_LEAN_AND_MEAN
-#  endif
-#  include <io.h>
+#  ifndef _WIN32
+#    include <unistd.h>
+#  else
+#    ifndef WIN32_LEAN_AND_MEAN
+#      define WIN32_LEAN_AND_MEAN
+#    endif
+#    include <io.h>
+#    include <windows.h>
+
+#    define O_CREAT _O_CREAT
+#    define O_TRUNC _O_TRUNC
+
+#    ifndef S_IRUSR
+#      define S_IRUSR _S_IREAD
+#    endif
+
+#    ifndef S_IWUSR
+#      define S_IWUSR _S_IWRITE
+#    endif
+
+#    ifdef __MINGW32__
+#      define _SH_DENYNO 0x40
+#    endif
+#  endif  // _WIN32
+#endif    // FMT_USE_FCNTL
+
+#ifdef _WIN32
 #  include <windows.h>
-
-#  define O_CREAT _O_CREAT
-#  define O_TRUNC _O_TRUNC
-
-#  ifndef S_IRUSR
-#    define S_IRUSR _S_IREAD
-#  endif
-
-#  ifndef S_IWUSR
-#    define S_IWUSR _S_IWRITE
-#  endif
-
-#  ifdef __MINGW32__
-#    define _SH_DENYNO 0x40
-#  endif
-#endif  // _WIN32
-#endif  // FMT_USE_FCNTL
+#endif
 
 #ifdef fileno
 #  undef fileno
@@ -58,7 +62,7 @@
 inline unsigned convert_rwcount(std::size_t count) {
   return count <= UINT_MAX ? static_cast<unsigned>(count) : UINT_MAX;
 }
-#else
+#elif FMT_USE_FCNTL
 // Return type of read and write functions.
 using RWResult = ssize_t;
 
@@ -68,6 +72,79 @@
 
 FMT_BEGIN_NAMESPACE
 
+#ifdef _WIN32
+detail::utf16_to_utf8::utf16_to_utf8(wstring_view s) {
+  if (int error_code = convert(s)) {
+    FMT_THROW(windows_error(error_code,
+                            "cannot convert string from UTF-16 to UTF-8"));
+  }
+}
+
+int detail::utf16_to_utf8::convert(wstring_view s) {
+  if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;
+  int s_size = static_cast<int>(s.size());
+  if (s_size == 0) {
+    // WideCharToMultiByte does not support zero length, handle separately.
+    buffer_.resize(1);
+    buffer_[0] = 0;
+    return 0;
+  }
+
+  int length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, nullptr, 0,
+                                   nullptr, nullptr);
+  if (length == 0) return GetLastError();
+  buffer_.resize(length + 1);
+  length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, &buffer_[0],
+                               length, nullptr, nullptr);
+  if (length == 0) return GetLastError();
+  buffer_[length] = 0;
+  return 0;
+}
+
+void windows_error::init(int err_code, string_view format_str,
+                         format_args args) {
+  error_code_ = err_code;
+  memory_buffer buffer;
+  detail::format_windows_error(buffer, err_code, vformat(format_str, args));
+  std::runtime_error& base = *this;
+  base = std::runtime_error(to_string(buffer));
+}
+
+void detail::format_windows_error(detail::buffer<char>& out, int error_code,
+                                  string_view message) FMT_NOEXCEPT {
+  FMT_TRY {
+    wmemory_buffer buf;
+    buf.resize(inline_buffer_size);
+    for (;;) {
+      wchar_t* system_message = &buf[0];
+      int result = FormatMessageW(
+          FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr,
+          error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), system_message,
+          static_cast<uint32_t>(buf.size()), nullptr);
+      if (result != 0) {
+        utf16_to_utf8 utf8_message;
+        if (utf8_message.convert(system_message) == ERROR_SUCCESS) {
+          format_to(buffer_appender<char>(out), "{}: {}", message,
+                    utf8_message);
+          return;
+        }
+        break;
+      }
+      if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
+        break;  // Can't get error message, report error code instead.
+      buf.resize(buf.size() * 2);
+    }
+  }
+  FMT_CATCH(...) {}
+  format_error_code(out, error_code, message);
+}
+
+void report_windows_error(int error_code,
+                          fmt::string_view message) FMT_NOEXCEPT {
+  report_error(detail::format_windows_error, error_code, message);
+}
+#endif  // _WIN32
+
 buffered_file::~buffered_file() FMT_NOEXCEPT {
   if (file_ && FMT_SYSTEM(fclose(file_)) != 0)
     report_system_error(errno, "cannot close file");
@@ -99,12 +176,12 @@
 #if FMT_USE_FCNTL
 file::file(cstring_view path, int oflag) {
   int mode = S_IRUSR | S_IWUSR;
-#if defined(_WIN32) && !defined(__MINGW32__)
+#  if defined(_WIN32) && !defined(__MINGW32__)
   fd_ = -1;
   FMT_POSIX_CALL(sopen_s(&fd_, path.c_str(), oflag, _SH_DENYNO, mode));
-#else
+#  else
   FMT_RETRY(fd_, FMT_POSIX_CALL(open(path.c_str(), oflag, mode)));
-#endif
+#  endif
   if (fd_ == -1)
     FMT_THROW(system_error(errno, "cannot open file {}", path.c_str()));
 }
@@ -126,7 +203,7 @@
 }
 
 long long file::size() const {
-#ifdef _WIN32
+#  ifdef _WIN32
   // Use GetFileSize instead of GetFileSizeEx for the case when _WIN32_WINNT
   // is less than 0x0500 as is the case with some default MinGW builds.
   // Both functions support large file sizes.
@@ -140,7 +217,7 @@
   }
   unsigned long long long_size = size_upper;
   return (long_size << sizeof(DWORD) * CHAR_BIT) | size_lower;
-#else
+#  else
   using Stat = struct stat;
   Stat file_stat = Stat();
   if (FMT_POSIX_CALL(fstat(fd_, &file_stat)) == -1)
@@ -148,21 +225,21 @@
   static_assert(sizeof(long long) >= sizeof(file_stat.st_size),
                 "return type of file::size is not large enough");
   return file_stat.st_size;
-#endif
+#  endif
 }
 
 std::size_t file::read(void* buffer, std::size_t count) {
   RWResult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(read(fd_, buffer, convert_rwcount(count))));
   if (result < 0) FMT_THROW(system_error(errno, "cannot read from file"));
-  return internal::to_unsigned(result);
+  return detail::to_unsigned(result);
 }
 
 std::size_t file::write(const void* buffer, std::size_t count) {
   RWResult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(write(fd_, buffer, convert_rwcount(count))));
   if (result < 0) FMT_THROW(system_error(errno, "cannot write to file"));
-  return internal::to_unsigned(result);
+  return detail::to_unsigned(result);
 }
 
 file file::dup(int fd) {
@@ -195,15 +272,15 @@
   read_end.close();
   write_end.close();
   int fds[2] = {};
-#ifdef _WIN32
+#  ifdef _WIN32
   // Make the default pipe capacity same as on Linux 2.6.11+.
   enum { DEFAULT_CAPACITY = 65536 };
   int result = FMT_POSIX_CALL(pipe(fds, DEFAULT_CAPACITY, _O_BINARY));
-#else
+#  else
   // Don't retry as the pipe function doesn't return EINTR.
   // http://pubs.opengroup.org/onlinepubs/009696799/functions/pipe.html
   int result = FMT_POSIX_CALL(pipe(fds));
-#endif
+#  endif
   if (result != 0) FMT_THROW(system_error(errno, "cannot create pipe"));
   // The following assignments don't throw because read_fd and write_fd
   // are closed.
@@ -212,8 +289,12 @@
 }
 
 buffered_file file::fdopen(const char* mode) {
-  // Don't retry as fdopen doesn't return EINTR.
+// Don't retry as fdopen doesn't return EINTR.
+#  if defined(__MINGW32__) && defined(_POSIX_)
+  FILE* f = ::fdopen(fd_, mode);
+#  else
   FILE* f = FMT_POSIX_CALL(fdopen(fd_, mode));
+#  endif
   if (!f)
     FMT_THROW(
         system_error(errno, "cannot associate stream with file descriptor"));
@@ -223,15 +304,19 @@
 }
 
 long getpagesize() {
-#ifdef _WIN32
+#  ifdef _WIN32
   SYSTEM_INFO si;
   GetSystemInfo(&si);
   return si.dwPageSize;
-#else
+#  else
   long size = FMT_POSIX_CALL(sysconf(_SC_PAGESIZE));
   if (size < 0) FMT_THROW(system_error(errno, "cannot get memory page size"));
   return size;
-#endif
+#  endif
+}
+
+FMT_API void ostream::grow(size_t) {
+  if (this->size() == this->capacity()) flush();
 }
 #endif  // FMT_USE_FCNTL
 FMT_END_NAMESPACE
diff --git a/support/README b/support/README
index e7fbacc..468f548 100644
--- a/support/README
+++ b/support/README
@@ -2,5 +2,3 @@
 
 * CMake modules
 * Build scripts
-* qmake (static build with dynamic libc only)
-
diff --git a/support/Vagrantfile b/support/Vagrantfile
index 24f166a..f6b5f93 100644
--- a/support/Vagrantfile
+++ b/support/Vagrantfile
@@ -4,6 +4,7 @@
 # A vagrant config for testing against gcc-4.8.
 Vagrant.configure("2") do |config|
   config.vm.box = "ubuntu/xenial64"
+  config.disksize.size = '15GB'
 
   config.vm.provider "virtualbox" do |vb|
     vb.memory = "4096"
diff --git a/support/cmake/JoinPaths.cmake b/support/cmake/JoinPaths.cmake
new file mode 100644
index 0000000..32d6d66
--- /dev/null
+++ b/support/cmake/JoinPaths.cmake
@@ -0,0 +1,26 @@
+# This module provides function for joining paths
+# known from from most languages
+#
+# Original license:
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Explicit permission given to distribute this module under
+# the terms of the project as described in /LICENSE.rst.
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()
diff --git a/support/cmake/cxx14.cmake b/support/cmake/cxx14.cmake
index 032fcb2..16ff575 100644
--- a/support/cmake/cxx14.cmake
+++ b/support/cmake/cxx14.cmake
@@ -48,17 +48,6 @@
 
 set(CMAKE_REQUIRED_FLAGS ${CXX_STANDARD_FLAG})
 
-# Check if variadic templates are working and not affected by GCC bug 39653:
-# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39653
-# Can be removed once gcc 4.4 support is dropped.
-check_cxx_source_compiles("
-  template <class T, class ...Types>
-  struct S { typedef typename S<Types...>::type type; };
-  int main() {}" SUPPORTS_VARIADIC_TEMPLATES)
-if (NOT SUPPORTS_VARIADIC_TEMPLATES)
-  set (SUPPORTS_VARIADIC_TEMPLATES OFF)
-endif ()
-
 # Check if user-defined literals are available
 check_cxx_source_compiles("
   void operator\"\" _udl(long double);
diff --git a/support/cmake/fmt.pc.in b/support/cmake/fmt.pc.in
index e935dc7..29976a8 100644
--- a/support/cmake/fmt.pc.in
+++ b/support/cmake/fmt.pc.in
@@ -1,11 +1,11 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=@CMAKE_INSTALL_PREFIX@
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@libdir_for_pc_file@
+includedir=@includedir_for_pc_file@
 
 Name: fmt
 Description: A modern formatting library
 Version: @FMT_VERSION@
-Libs: -L${libdir} -lfmt
+Libs: -L${libdir} -l@FMT_LIB_NAME@
 Cflags: -I${includedir}
 
diff --git a/support/fmt.pro b/support/fmt.pro
deleted file mode 100644
index c555d0b..0000000
--- a/support/fmt.pro
+++ /dev/null
@@ -1,27 +0,0 @@
-# Staticlib configuration for qmake builds
-# For some reason qmake 3.1 fails to identify source dependencies and excludes format.cc and printf.cc
-# from compilation so it _MUST_ be called as qmake -nodepend
-# A workaround is implemented below: a custom compiler is defined which does not track dependencies
-
-TEMPLATE = lib
-
-TARGET = fmt
-
-QMAKE_EXT_CPP = .cc
-
-CONFIG = staticlib warn_on c++11
-
-FMT_SOURCES = \
-    ../src/format.cc \
-    ../src/posix.cc
-
-fmt.name = libfmt
-fmt.input = FMT_SOURCES
-fmt.output = ${QMAKE_FILE_BASE}$$QMAKE_EXT_OBJ
-fmt.clean = ${QMAKE_FILE_BASE}$$QMAKE_EXT_OBJ
-fmt.depends = ${QMAKE_FILE_IN}
-# QMAKE_RUN_CXX will not be expanded
-fmt.commands = $$QMAKE_CXX -c $$QMAKE_CXXFLAGS $$QMAKE_CXXFLAGS_WARN_ON $$QMAKE_CXXFLAGS_RELEASE_WITH_DEBUGINFO $$QMAKE_CXXFLAGS_CXX11 ${QMAKE_FILE_IN}
-fmt.variable_out = OBJECTS
-fmt.CONFIG = no_dependencies no_link
-QMAKE_EXTRA_COMPILERS += fmt
diff --git a/support/manage.py b/support/manage.py
index e39beff..9f27066 100755
--- a/support/manage.py
+++ b/support/manage.py
@@ -137,15 +137,40 @@
         if not os.path.exists(contents):
             os.rename(os.path.join(target_doc_dir, 'index.rst'), contents)
         # Fix issues in reference.rst/api.rst.
-        for filename in ['reference.rst', 'api.rst']:
+        for filename in ['reference.rst', 'api.rst', 'index.rst']:
             pattern = re.compile('doxygenfunction.. (bin|oct|hexu|hex)$', re.M)
             with rewrite(os.path.join(target_doc_dir, filename)) as b:
                 b.data = b.data.replace('std::ostream &', 'std::ostream&')
                 b.data = re.sub(pattern, r'doxygenfunction:: \1(int)', b.data)
                 b.data = b.data.replace('std::FILE*', 'std::FILE *')
                 b.data = b.data.replace('unsigned int', 'unsigned')
-                b.data = b.data.replace('operator""_', 'operator"" _')
-                b.data = b.data.replace(', size_t', ', std::size_t')
+                #b.data = b.data.replace('operator""_', 'operator"" _')
+                b.data = b.data.replace(
+                    'format_to_n(OutputIt, size_t, string_view, Args&&',
+                    'format_to_n(OutputIt, size_t, const S&, const Args&')
+                b.data = b.data.replace(
+                    'format_to_n(OutputIt, std::size_t, string_view, Args&&',
+                    'format_to_n(OutputIt, std::size_t, const S&, const Args&')
+                if version == ('3.0.2'):
+                    b.data = b.data.replace(
+                        'fprintf(std::ostream&', 'fprintf(std::ostream &')
+                if version == ('5.3.0'):
+                    b.data = b.data.replace(
+                        'format_to(OutputIt, const S&, const Args&...)',
+                        'format_to(OutputIt, const S &, const Args &...)')
+                if version.startswith('5.') or version.startswith('6.'):
+                    b.data = b.data.replace(', size_t', ', std::size_t')
+                if version.startswith('7.'):
+                    b.data = b.data.replace(', std::size_t', ', size_t')
+                    b.data = b.data.replace('join(It, It', 'join(It, Sentinel')
+                b.data = b.data.replace('aa long', 'a long')
+                b.data = b.data.replace('serveral', 'several')
+                if version.startswith('6.2.'):
+                    b.data = b.data.replace(
+                        'vformat(const S&, basic_format_args<' +
+                        'buffer_context<Char>>)',
+                        'vformat(const S&, basic_format_args<' +
+                        'buffer_context<type_identity_t<Char>>>)')
         # Fix a broken link in index.rst.
         index = os.path.join(target_doc_dir, 'index.rst')
         with rewrite(index) as b:
diff --git a/support/update-coverity-branch.py b/support/update-coverity-branch.py
deleted file mode 100755
index 519f5d0..0000000
--- a/support/update-coverity-branch.py
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/usr/bin/env python
-# Update the coverity branch from the master branch.
-# It is not done automatically because Coverity Scan limits
-# the number of submissions per day.
-
-from __future__ import print_function
-import shutil, tempfile
-from subprocess import check_output, STDOUT
-
-class Git:
-    def __init__(self, dir):
-        self.dir = dir
-
-    def __call__(self, *args):
-        output = check_output(['git'] + list(args), cwd=self.dir, stderr=STDOUT)
-        print(output)
-        return output
-
-dir = tempfile.mkdtemp()
-try:
-    git = Git(dir)
-    git('clone', '-b', 'coverity', 'git@github.com:fmtlib/fmt.git', dir)
-    output = git('merge', '-X', 'theirs', '--no-commit', 'origin/master')
-    if 'Fast-forward' not in output:
-        git('reset', 'HEAD', '.travis.yml')
-        git('checkout', '--', '.travis.yml')
-        git('commit', '-m', 'Update coverity branch')
-    git('push')
-finally:
-    shutil.rmtree(dir)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 8aab2c9..7ae5659 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -17,9 +17,7 @@
   target_compile_definitions(gmock PUBLIC GTEST_HAS_PTHREAD=0)
 endif ()
 
-if (NOT SUPPORTS_VARIADIC_TEMPLATES)
-  target_compile_definitions(gmock PUBLIC GTEST_LANG_CXX11=0)
-endif ()
+target_compile_definitions(gmock PUBLIC GTEST_LANG_CXX11=0)
 
 if (MSVC)
   # Workaround a bug in implementation of variadic templates in MSVC11.
@@ -93,8 +91,6 @@
 add_fmt_test(chrono-test)
 add_fmt_test(color-test)
 add_fmt_test(core-test)
-add_fmt_test(grisu-test)
-target_compile_definitions(grisu-test PRIVATE FMT_USE_GRISU=1)
 add_fmt_test(gtest-extra-test)
 add_fmt_test(format-test mock-allocator.h)
 if (MSVC)
@@ -107,11 +103,21 @@
 add_fmt_test(ostream-test)
 add_fmt_test(compile-test)
 add_fmt_test(printf-test)
-add_fmt_test(custom-formatter-test)
 add_fmt_test(ranges-test)
 add_fmt_test(scan-test)
 
-if (NOT MSVC_BUILD_STATIC)
+if (NOT DEFINED MSVC_STATIC_RUNTIME AND MSVC)
+  foreach (flag_var
+			 CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+			 CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+	if (${flag_var} MATCHES "^(/|-)(MT|MTd)")
+	  set(MSVC_STATIC_RUNTIME ON)
+	  break()
+	endif()
+  endforeach()
+endif()
+
+if (NOT MSVC_STATIC_RUNTIME)
   add_fmt_executable(posix-mock-test
     posix-mock-test.cc ../src/format.cc ${TEST_MAIN_SRC})
   target_include_directories(
@@ -125,7 +131,7 @@
     target_compile_definitions(posix-mock-test PRIVATE FMT_LOCALE)
   endif ()
   add_test(NAME posix-mock-test COMMAND posix-mock-test)
-  add_fmt_test(posix-test)
+  add_fmt_test(os-test)
 endif ()
 
 add_fmt_executable(header-only-test
@@ -171,18 +177,6 @@
   target_compile_definitions(
     nolocale-test PRIVATE FMT_STATIC_THOUSANDS_SEPARATOR=1)
 
-  # Test that the library compiles without windows.h.
-  if (CMAKE_SYSTEM_NAME STREQUAL "Windows")
-    add_library(no-windows-h-test ../src/format.cc)
-    target_include_directories(
-      no-windows-h-test PRIVATE ${PROJECT_SOURCE_DIR}/include)
-    target_compile_definitions(no-windows-h-test PRIVATE FMT_USE_WINDOWS_H=0)
-    if (FMT_PEDANTIC)
-      target_compile_options(no-windows-h-test PRIVATE ${PEDANTIC_COMPILE_FLAGS})
-    endif ()
-    target_include_directories(no-windows-h-test SYSTEM PUBLIC gtest gmock)
-  endif ()
-
   add_test(compile-error-test ${CMAKE_CTEST_COMMAND}
     --build-and-test
     "${CMAKE_CURRENT_SOURCE_DIR}/compile-error-test"
@@ -229,20 +223,22 @@
     "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}")
 endif ()
 
-# Activate optional CUDA tests if CUDA is found. For version selection, see
+# Activate optional CUDA tests if CUDA is found. For version selection see
 # https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#cpp14-language-features
-if (${CMAKE_VERSION} VERSION_LESS 3.15)
-  find_package(CUDA 9.0)
-else ()
-  include(CheckLanguage)
-  check_language(CUDA)
-  if (CMAKE_CUDA_COMPILER)
-    enable_language(CUDA OPTIONAL)
-    set(CUDA_FOUND TRUE)
+if (FMT_CUDA_TEST)
+  if (${CMAKE_VERSION} VERSION_LESS 3.15)
+    find_package(CUDA 9.0)
+  else ()
+    include(CheckLanguage)
+    check_language(CUDA)
+    if (CMAKE_CUDA_COMPILER)
+      enable_language(CUDA OPTIONAL)
+      set(CUDA_FOUND TRUE)
+    endif ()
   endif ()
-endif ()
 
-if (CUDA_FOUND)
-  add_subdirectory(cuda-test)
-  add_test(NAME cuda-test COMMAND fmt-in-cuda-test)
+  if (CUDA_FOUND)
+    add_subdirectory(cuda-test)
+    add_test(NAME cuda-test COMMAND fmt-in-cuda-test)
+  endif ()
 endif ()
diff --git a/test/add-subdirectory-test/CMakeLists.txt b/test/add-subdirectory-test/CMakeLists.txt
index db7054b..9cc4b0e 100644
--- a/test/add-subdirectory-test/CMakeLists.txt
+++ b/test/add-subdirectory-test/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1.0)
+cmake_minimum_required(VERSION 3.1...3.18)
 
 project(fmt-test)
 
diff --git a/test/assert-test.cc b/test/assert-test.cc
index 26a87a7..70efa38 100644
--- a/test/assert-test.cc
+++ b/test/assert-test.cc
@@ -1,4 +1,8 @@
-// Formatting library for C++ - assertion tests
+// Formatting library for C++ - FMT_ASSERT test
+//
+// It is a separate test to minimize the number of EXPECT_DEBUG_DEATH checks
+// which are slow on some platforms. In other tests FMT_ASSERT is made to throw
+// an exception which is much faster and easier to check.
 //
 // Copyright (c) 2012 - present, Victor Zverovich
 // All rights reserved.
@@ -8,17 +12,12 @@
 #include "fmt/core.h"
 #include "gtest.h"
 
-#if GTEST_HAS_DEATH_TEST
-#  define EXPECT_DEBUG_DEATH_IF_SUPPORTED(statement, regex) \
-    EXPECT_DEBUG_DEATH(statement, regex)
-#else
-#  define EXPECT_DEBUG_DEATH_IF_SUPPORTED(statement, regex) \
-    GTEST_UNSUPPORTED_DEATH_TEST_(statement, regex, )
-#endif
-
 TEST(AssertTest, Fail) {
-  EXPECT_DEBUG_DEATH_IF_SUPPORTED(FMT_ASSERT(false, "don't panic!"),
-                                  "don't panic!");
+#if GTEST_HAS_DEATH_TEST
+  EXPECT_DEBUG_DEATH(FMT_ASSERT(false, "don't panic!"), "don't panic!");
+#else
+  fmt::print("warning: death tests are not supported\n");
+#endif
 }
 
 bool test_condition = false;
diff --git a/test/chrono-test.cc b/test/chrono-test.cc
index 04b5f2f..fa383c1 100644
--- a/test/chrono-test.cc
+++ b/test/chrono-test.cc
@@ -10,10 +10,11 @@
 #endif
 
 #include "fmt/chrono.h"
-#include "gtest-extra.h"
 
 #include <iomanip>
 
+#include "gtest-extra.h"
+
 std::tm make_tm() {
   auto time = std::tm();
   time.tm_mday = 1;
@@ -94,6 +95,17 @@
   EXPECT_TRUE(EqualTime(tm, fmt::gmtime(t)));
 }
 
+TEST(TimeTest, TimePoint) {
+  std::chrono::system_clock::time_point point = std::chrono::system_clock::now();
+
+  std::time_t t = std::chrono::system_clock::to_time_t(point);
+  std::tm tm = *std::localtime(&t);
+  char strftime_output[256];
+  std::strftime(strftime_output, sizeof(strftime_output), "It is %Y-%m-%d %H:%M:%S", &tm);
+
+  EXPECT_EQ(strftime_output, fmt::format("It is {:%Y-%m-%d %H:%M:%S}", point));
+}
+
 #define EXPECT_TIME(spec, time, duration)                 \
   {                                                       \
     std::locale loc("ja_JP.utf8");                        \
@@ -145,6 +157,48 @@
       fmt::format("{}", std::chrono::duration<int, std::ratio<15, 4>>(42)));
 }
 
+TEST(ChronoTest, FormatWide) {
+  EXPECT_EQ(L"42s", fmt::format(L"{}", std::chrono::seconds(42)));
+  EXPECT_EQ(L"42as",
+            fmt::format(L"{}", std::chrono::duration<int, std::atto>(42)));
+  EXPECT_EQ(L"42fs",
+            fmt::format(L"{}", std::chrono::duration<int, std::femto>(42)));
+  EXPECT_EQ(L"42ps",
+            fmt::format(L"{}", std::chrono::duration<int, std::pico>(42)));
+  EXPECT_EQ(L"42ns", fmt::format(L"{}", std::chrono::nanoseconds(42)));
+  EXPECT_EQ(L"42\u00B5s", fmt::format(L"{}", std::chrono::microseconds(42)));
+  EXPECT_EQ(L"42ms", fmt::format(L"{}", std::chrono::milliseconds(42)));
+  EXPECT_EQ(L"42cs",
+            fmt::format(L"{}", std::chrono::duration<int, std::centi>(42)));
+  EXPECT_EQ(L"42ds",
+            fmt::format(L"{}", std::chrono::duration<int, std::deci>(42)));
+  EXPECT_EQ(L"42s", fmt::format(L"{}", std::chrono::seconds(42)));
+  EXPECT_EQ(L"42das",
+            fmt::format(L"{}", std::chrono::duration<int, std::deca>(42)));
+  EXPECT_EQ(L"42hs",
+            fmt::format(L"{}", std::chrono::duration<int, std::hecto>(42)));
+  EXPECT_EQ(L"42ks",
+            fmt::format(L"{}", std::chrono::duration<int, std::kilo>(42)));
+  EXPECT_EQ(L"42Ms",
+            fmt::format(L"{}", std::chrono::duration<int, std::mega>(42)));
+  EXPECT_EQ(L"42Gs",
+            fmt::format(L"{}", std::chrono::duration<int, std::giga>(42)));
+  EXPECT_EQ(L"42Ts",
+            fmt::format(L"{}", std::chrono::duration<int, std::tera>(42)));
+  EXPECT_EQ(L"42Ps",
+            fmt::format(L"{}", std::chrono::duration<int, std::peta>(42)));
+  EXPECT_EQ(L"42Es",
+            fmt::format(L"{}", std::chrono::duration<int, std::exa>(42)));
+  EXPECT_EQ(L"42m", fmt::format(L"{}", std::chrono::minutes(42)));
+  EXPECT_EQ(L"42h", fmt::format(L"{}", std::chrono::hours(42)));
+  EXPECT_EQ(
+      L"42[15]s",
+      fmt::format(L"{}", std::chrono::duration<int, std::ratio<15, 1>>(42)));
+  EXPECT_EQ(
+      L"42[15/4]s",
+      fmt::format(L"{}", std::chrono::duration<int, std::ratio<15, 4>>(42)));
+}
+
 TEST(ChronoTest, Align) {
   auto s = std::chrono::seconds(42);
   EXPECT_EQ("42s  ", fmt::format("{:5}", s));
diff --git a/test/color-test.cc b/test/color-test.cc
index fde3a0c..3073808 100644
--- a/test/color-test.cc
+++ b/test/color-test.cc
@@ -6,6 +6,11 @@
 // For the license information refer to format.h.
 
 #include "fmt/color.h"
+
+#include <iterator>
+#include <string>
+#include <utility>
+
 #include "gtest-extra.h"
 
 TEST(ColorsTest, ColorsPrint) {
@@ -50,6 +55,8 @@
 TEST(ColorsTest, Format) {
   EXPECT_EQ(fmt::format(fg(fmt::rgb(255, 20, 30)), "rgb(255,20,30)"),
             "\x1b[38;2;255;020;030mrgb(255,20,30)\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::rgb(255, 20, 30)), L"rgb(255,20,30) wide"),
+            L"\x1b[38;2;255;020;030mrgb(255,20,30) wide\x1b[0m");
   EXPECT_EQ(fmt::format(fg(fmt::color::blue), "blue"),
             "\x1b[38;2;000;000;255mblue\x1b[0m");
   EXPECT_EQ(
@@ -81,3 +88,12 @@
   EXPECT_EQ(fmt::format(fg(fmt::terminal_color::red), "{}", "foo"),
             "\x1b[31mfoo\x1b[0m");
 }
+
+TEST(ColorsTest, FormatToOutAcceptsTextStyle) {
+  fmt::text_style ts = fg(fmt::rgb(255, 20, 30));
+  std::string out;
+  fmt::format_to(std::back_inserter(out), ts, "rgb(255,20,30){}{}{}", 1, 2, 3);
+
+  EXPECT_EQ(fmt::to_string(out),
+            "\x1b[38;2;255;020;030mrgb(255,20,30)123\x1b[0m");
+}
diff --git a/test/compile-error-test/CMakeLists.txt b/test/compile-error-test/CMakeLists.txt
index 75a0c5a..8202f27 100644
--- a/test/compile-error-test/CMakeLists.txt
+++ b/test/compile-error-test/CMakeLists.txt
@@ -1,6 +1,6 @@
 # Test if compile errors are produced where necessary.
 
-cmake_minimum_required(VERSION 3.1.0)
+cmake_minimum_required(VERSION 3.1...3.18)
 
 include(CheckCXXSourceCompiles)
 include(CheckCXXCompilerFlag)
diff --git a/test/compile-test.cc b/test/compile-test.cc
index 13bef48..c0dda50 100644
--- a/test/compile-test.cc
+++ b/test/compile-test.cc
@@ -5,18 +5,10 @@
 //
 // For the license information refer to format.h.
 
-#include <stdint.h>
-#include <cctype>
-#include <cfloat>
-#include <climits>
-#include <cmath>
-#include <cstring>
-#include <deque>
-#include <list>
-#include <memory>
 #include <string>
+#include <type_traits>
 
-// Check if fmt/compile.h compiles with windows.h included before it.
+// Check that fmt/compile.h compiles with windows.h included before it.
 #ifdef _WIN32
 #  include <windows.h>
 #endif
@@ -24,23 +16,15 @@
 #include "fmt/compile.h"
 #include "gmock.h"
 #include "gtest-extra.h"
-#include "mock-allocator.h"
 #include "util.h"
 
-#undef ERROR
-#undef min
-#undef max
-
-using testing::Return;
-using testing::StrictMock;
-
 // compiletime_prepared_parts_type_provider is useful only with relaxed
 // constexpr.
 #if FMT_USE_CONSTEXPR
 template <unsigned EXPECTED_PARTS_COUNT, typename Format>
 void check_prepared_parts_type(Format format) {
-  typedef fmt::internal::compiled_format_base<decltype(format)> provider;
-  typedef fmt::internal::format_part<char>
+  typedef fmt::detail::compiled_format_base<decltype(format)> provider;
+  typedef fmt::detail::format_part<char>
       expected_parts_type[EXPECTED_PARTS_COUNT];
   static_assert(std::is_same<typename provider::parts_container,
                              expected_parts_type>::value,
@@ -66,46 +50,37 @@
 #endif
 
 TEST(CompileTest, PassStringLiteralFormat) {
-  const auto prepared = fmt::compile<int>("test {}");
+  const auto prepared = fmt::detail::compile<int>("test {}");
   EXPECT_EQ("test 42", fmt::format(prepared, 42));
-  const auto wprepared = fmt::compile<int>(L"test {}");
+  const auto wprepared = fmt::detail::compile<int>(L"test {}");
   EXPECT_EQ(L"test 42", fmt::format(wprepared, 42));
 }
 
-#if FMT_USE_CONSTEXPR
-TEST(CompileTest, PassCompileString) {
-  const auto prepared = fmt::compile<int>(FMT_STRING("test {}"));
-  EXPECT_EQ("test 42", fmt::format(prepared, 42));
-  const auto wprepared = fmt::compile<int>(FMT_STRING(L"test {}"));
-  EXPECT_EQ(L"test 42", fmt::format(wprepared, 42));
-}
-#endif
-
 TEST(CompileTest, FormatToArrayOfChars) {
   char buffer[32] = {0};
-  const auto prepared = fmt::compile<int>("4{}");
-  fmt::format_to(fmt::internal::make_checked(buffer, 32), prepared, 2);
+  const auto prepared = fmt::detail::compile<int>("4{}");
+  fmt::format_to(fmt::detail::make_checked(buffer, 32), prepared, 2);
   EXPECT_EQ(std::string("42"), buffer);
   wchar_t wbuffer[32] = {0};
-  const auto wprepared = fmt::compile<int>(L"4{}");
-  fmt::format_to(fmt::internal::make_checked(wbuffer, 32), wprepared, 2);
+  const auto wprepared = fmt::detail::compile<int>(L"4{}");
+  fmt::format_to(fmt::detail::make_checked(wbuffer, 32), wprepared, 2);
   EXPECT_EQ(std::wstring(L"42"), wbuffer);
 }
 
 TEST(CompileTest, FormatToIterator) {
   std::string s(2, ' ');
-  const auto prepared = fmt::compile<int>("4{}");
+  const auto prepared = fmt::detail::compile<int>("4{}");
   fmt::format_to(s.begin(), prepared, 2);
   EXPECT_EQ("42", s);
   std::wstring ws(2, L' ');
-  const auto wprepared = fmt::compile<int>(L"4{}");
+  const auto wprepared = fmt::detail::compile<int>(L"4{}");
   fmt::format_to(ws.begin(), wprepared, 2);
   EXPECT_EQ(L"42", ws);
 }
 
 TEST(CompileTest, FormatToN) {
   char buf[5];
-  auto f = fmt::compile<int>("{:10}");
+  auto f = fmt::detail::compile<int>("{:10}");
   auto result = fmt::format_to_n(buf, 5, f, 42);
   EXPECT_EQ(result.size, 10);
   EXPECT_EQ(result.out, buf + 5);
@@ -113,31 +88,86 @@
 }
 
 TEST(CompileTest, FormattedSize) {
-  auto f = fmt::compile<int>("{:10}");
+  auto f = fmt::detail::compile<int>("{:10}");
   EXPECT_EQ(fmt::formatted_size(f, 42), 10);
 }
 
 TEST(CompileTest, MultipleTypes) {
-  auto f = fmt::compile<int, int>("{} {}");
+  auto f = fmt::detail::compile<int, int>("{} {}");
   EXPECT_EQ(fmt::format(f, 42, 42), "42 42");
 }
 
-struct formattable {};
+struct test_formattable {};
 
 FMT_BEGIN_NAMESPACE
-template <> struct formatter<formattable> : formatter<const char*> {
-  auto format(formattable, format_context& ctx) -> decltype(ctx.out()) {
+template <> struct formatter<test_formattable> : formatter<const char*> {
+  template <typename FormatContext>
+  auto format(test_formattable, FormatContext& ctx) -> decltype(ctx.out()) {
     return formatter<const char*>::format("foo", ctx);
   }
 };
 FMT_END_NAMESPACE
 
 TEST(CompileTest, FormatUserDefinedType) {
-  auto f = fmt::compile<formattable>("{}");
-  EXPECT_EQ(fmt::format(f, formattable()), "foo");
+  auto f = fmt::detail::compile<test_formattable>("{}");
+  EXPECT_EQ(fmt::format(f, test_formattable()), "foo");
 }
 
 TEST(CompileTest, EmptyFormatString) {
-  auto f = fmt::compile<>("");
+  auto f = fmt::detail::compile<>("");
   EXPECT_EQ(fmt::format(f), "");
 }
+
+#ifdef __cpp_if_constexpr
+TEST(CompileTest, FormatDefault) {
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42));
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42u));
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42ll));
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42ull));
+  EXPECT_EQ("true", fmt::format(FMT_COMPILE("{}"), true));
+  EXPECT_EQ("x", fmt::format(FMT_COMPILE("{}"), 'x'));
+  EXPECT_EQ("4.2", fmt::format(FMT_COMPILE("{}"), 4.2));
+  EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), "foo"));
+  EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), std::string("foo")));
+  EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), test_formattable()));
+}
+
+TEST(CompileTest, FormatWideString) {
+  EXPECT_EQ(L"42", fmt::format(FMT_COMPILE(L"{}"), 42));
+}
+
+TEST(CompileTest, FormatSpecs) {
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{:x}"), 0x42));
+}
+
+TEST(CompileTest, DynamicWidth) {
+  EXPECT_EQ("  42foo  ",
+            fmt::format(FMT_COMPILE("{:{}}{:{}}"), 42, 4, "foo", 5));
+}
+
+TEST(CompileTest, FormatTo) {
+  char buf[8];
+  auto end = fmt::format_to(buf, FMT_COMPILE("{}"), 42);
+  *end = '\0';
+  EXPECT_STREQ("42", buf);
+  end = fmt::format_to(buf, FMT_COMPILE("{:x}"), 42);
+  *end = '\0';
+  EXPECT_STREQ("2a", buf);
+}
+
+TEST(CompileTest, FormatToNWithCompileMacro) {
+  constexpr auto buffer_size = 8;
+  char buffer[buffer_size];
+  auto res = fmt::format_to_n(buffer, buffer_size, FMT_COMPILE("{}"), 42);
+  *res.out = '\0';
+  EXPECT_STREQ("42", buffer);
+  res = fmt::format_to_n(buffer, buffer_size, FMT_COMPILE("{:x}"), 42);
+  *res.out = '\0';
+  EXPECT_STREQ("2a", buffer);
+}
+
+TEST(CompileTest, TextAndArg) {
+  EXPECT_EQ(">>>42<<<", fmt::format(FMT_COMPILE(">>>{}<<<"), 42));
+  EXPECT_EQ("42!", fmt::format(FMT_COMPILE("{}!"), 42));
+}
+#endif
diff --git a/test/core-test.cc b/test/core-test.cc
index e2eec3e..9d88070 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -15,9 +15,8 @@
 #include <string>
 #include <type_traits>
 
-#include "test-assert.h"
-
 #include "gmock.h"
+#include "test-assert.h"
 
 // Check if fmt/core.h compiles with windows.h included before it.
 #ifdef _WIN32
@@ -31,22 +30,17 @@
 
 using fmt::basic_format_arg;
 using fmt::string_view;
-using fmt::internal::buffer;
-using fmt::internal::value;
+using fmt::detail::buffer;
+using fmt::detail::make_arg;
+using fmt::detail::value;
 
 using testing::_;
+using testing::Invoke;
+using testing::Return;
 using testing::StrictMock;
 
-namespace {
-
 struct test_struct {};
 
-template <typename Context, typename T>
-basic_format_arg<Context> make_arg(const T& value) {
-  return fmt::internal::make_arg<Context>(value);
-}
-}  // namespace
-
 FMT_BEGIN_NAMESPACE
 template <typename Char> struct formatter<test_struct, Char> {
   template <typename ParseContext>
@@ -54,10 +48,7 @@
     return ctx.begin();
   }
 
-  typedef std::back_insert_iterator<buffer<Char>> iterator;
-
-  auto format(test_struct, basic_format_context<iterator, char>& ctx)
-      -> decltype(ctx.out()) {
+  auto format(test_struct, format_context& ctx) -> decltype(ctx.out()) {
     const Char* test = "test";
     return std::copy_n(test, std::strlen(test), ctx.out());
   }
@@ -82,22 +73,22 @@
 }
 #endif
 
-// A test buffer with a dummy grow method.
-template <typename T> struct test_buffer : buffer<T> {
-  void grow(std::size_t capacity) { this->set(nullptr, capacity); }
-};
+TEST(BufferTest, Indestructible) {
+  static_assert(!std::is_destructible<fmt::detail::buffer<int>>(),
+                "buffer's destructor is protected");
+}
 
-template <typename T> struct mock_buffer : buffer<T> {
-  MOCK_METHOD1(do_grow, void(std::size_t capacity));
+template <typename T> struct mock_buffer final : buffer<T> {
+  MOCK_METHOD1(do_grow, size_t(size_t capacity));
 
-  void grow(std::size_t capacity) {
-    this->set(this->data(), capacity);
-    do_grow(capacity);
+  void grow(size_t capacity) { this->set(this->data(), do_grow(capacity)); }
+
+  mock_buffer(T* data = nullptr, size_t capacity = 0) {
+    this->set(data, capacity);
+    ON_CALL(*this, do_grow(_)).WillByDefault(Invoke([](size_t capacity) {
+      return capacity;
+    }));
   }
-
-  mock_buffer() {}
-  mock_buffer(T* data) { this->set(data, 0); }
-  mock_buffer(T* data, std::size_t capacity) { this->set(data, capacity); }
 };
 
 TEST(BufferTest, Ctor) {
@@ -116,7 +107,7 @@
   }
   {
     int dummy;
-    std::size_t capacity = std::numeric_limits<std::size_t>::max();
+    size_t capacity = std::numeric_limits<size_t>::max();
     mock_buffer<int> buffer(&dummy, capacity);
     EXPECT_EQ(&dummy, &buffer[0]);
     EXPECT_EQ(static_cast<size_t>(0), buffer.size());
@@ -124,24 +115,6 @@
   }
 }
 
-struct dying_buffer : test_buffer<int> {
-  MOCK_METHOD0(die, void());
-  ~dying_buffer() { die(); }
-
- private:
-  virtual void avoid_weak_vtable();
-};
-
-void dying_buffer::avoid_weak_vtable() {}
-
-TEST(BufferTest, VirtualDtor) {
-  typedef StrictMock<dying_buffer> stict_mock_buffer;
-  stict_mock_buffer* mock_buffer = new stict_mock_buffer();
-  EXPECT_CALL(*mock_buffer, die());
-  buffer<int>* buffer = mock_buffer;
-  delete buffer;
-}
-
 TEST(BufferTest, Access) {
   char data[10];
   mock_buffer<char> buffer(data, sizeof(data));
@@ -149,34 +122,44 @@
   EXPECT_EQ(11, buffer[0]);
   buffer[3] = 42;
   EXPECT_EQ(42, *(&buffer[0] + 3));
-  const fmt::internal::buffer<char>& const_buffer = buffer;
+  const fmt::detail::buffer<char>& const_buffer = buffer;
   EXPECT_EQ(42, const_buffer[3]);
 }
 
-TEST(BufferTest, Resize) {
+TEST(BufferTest, TryResize) {
   char data[123];
   mock_buffer<char> buffer(data, sizeof(data));
   buffer[10] = 42;
   EXPECT_EQ(42, buffer[10]);
-  buffer.resize(20);
+  buffer.try_resize(20);
   EXPECT_EQ(20u, buffer.size());
   EXPECT_EQ(123u, buffer.capacity());
   EXPECT_EQ(42, buffer[10]);
-  buffer.resize(5);
+  buffer.try_resize(5);
   EXPECT_EQ(5u, buffer.size());
   EXPECT_EQ(123u, buffer.capacity());
   EXPECT_EQ(42, buffer[10]);
-  // Check if resize calls grow.
+  // Check if try_resize calls grow.
   EXPECT_CALL(buffer, do_grow(124));
-  buffer.resize(124);
+  buffer.try_resize(124);
   EXPECT_CALL(buffer, do_grow(200));
-  buffer.resize(200);
+  buffer.try_resize(200);
+}
+
+TEST(BufferTest, TryResizePartial) {
+  char data[10];
+  mock_buffer<char> buffer(data, sizeof(data));
+  EXPECT_CALL(buffer, do_grow(20)).WillOnce(Return(15));
+  buffer.try_resize(20);
+  EXPECT_EQ(buffer.capacity(), 15);
+  EXPECT_EQ(buffer.size(), 15);
 }
 
 TEST(BufferTest, Clear) {
-  test_buffer<char> buffer;
-  buffer.resize(20);
-  buffer.resize(0);
+  mock_buffer<char> buffer;
+  EXPECT_CALL(buffer, do_grow(20));
+  buffer.try_resize(20);
+  buffer.try_resize(0);
   EXPECT_EQ(static_cast<size_t>(0), buffer.size());
   EXPECT_EQ(20u, buffer.capacity());
 }
@@ -184,11 +167,11 @@
 TEST(BufferTest, Append) {
   char data[15];
   mock_buffer<char> buffer(data, 10);
-  const char* test = "test";
+  auto test = "test";
   buffer.append(test, test + 5);
   EXPECT_STREQ(test, &buffer[0]);
   EXPECT_EQ(5u, buffer.size());
-  buffer.resize(10);
+  buffer.try_resize(10);
   EXPECT_CALL(buffer, do_grow(12));
   buffer.append(test, test + 2);
   EXPECT_EQ('t', buffer[10]);
@@ -196,22 +179,37 @@
   EXPECT_EQ(12u, buffer.size());
 }
 
+TEST(BufferTest, AppendPartial) {
+  char data[10];
+  mock_buffer<char> buffer(data, sizeof(data));
+  testing::InSequence seq;
+  EXPECT_CALL(buffer, do_grow(15)).WillOnce(Return(10));
+  EXPECT_CALL(buffer, do_grow(15)).WillOnce(Invoke([&buffer](size_t) {
+    EXPECT_EQ(fmt::string_view(buffer.data(), buffer.size()), "0123456789");
+    buffer.clear();
+    return 10;
+  }));
+  auto test = "0123456789abcde";
+  buffer.append(test, test + 15);
+}
+
 TEST(BufferTest, AppendAllocatesEnoughStorage) {
   char data[19];
   mock_buffer<char> buffer(data, 10);
-  const char* test = "abcdefgh";
-  buffer.resize(10);
+  auto test = "abcdefgh";
+  buffer.try_resize(10);
   EXPECT_CALL(buffer, do_grow(19));
   buffer.append(test, test + 9);
 }
 
 TEST(ArgTest, FormatArgs) {
-  fmt::format_args args;
+  auto args = fmt::format_args();
   EXPECT_FALSE(args.get(1));
 }
 
 struct custom_context {
-  typedef char char_type;
+  using char_type = char;
+  using parse_context_type = fmt::format_parse_context;
 
   template <typename T> struct formatter_type {
     template <typename ParseContext>
@@ -233,21 +231,21 @@
 };
 
 TEST(ArgTest, MakeValueWithCustomContext) {
-  test_struct t;
-  fmt::internal::value<custom_context> arg(
-      fmt::internal::arg_mapper<custom_context>().map(t));
+  auto t = test_struct();
+  fmt::detail::value<custom_context> arg(
+      fmt::detail::arg_mapper<custom_context>().map(t));
   custom_context ctx = {false, fmt::format_parse_context("")};
   arg.custom.format(&t, ctx.parse_context(), ctx);
   EXPECT_TRUE(ctx.called);
 }
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 template <typename Char>
 bool operator==(custom_value<Char> lhs, custom_value<Char> rhs) {
   return lhs.value == rhs.value;
 }
-}  // namespace internal
+}  // namespace detail
 FMT_END_NAMESPACE
 
 // Use a unique result type to make sure that there are no undesirable
@@ -255,10 +253,10 @@
 struct test_result {};
 
 template <typename T> struct mock_visitor {
-  template <typename U> struct result { typedef test_result type; };
+  template <typename U> struct result { using type = test_result; };
 
   mock_visitor() {
-    ON_CALL(*this, visit(_)).WillByDefault(testing::Return(test_result()));
+    ON_CALL(*this, visit(_)).WillByDefault(Return(test_result()));
   }
 
   MOCK_METHOD1_T(visit, test_result(T value));
@@ -272,10 +270,10 @@
   }
 };
 
-template <typename T> struct visit_type { typedef T Type; };
+template <typename T> struct visit_type { using type = T; };
 
-#define VISIT_TYPE(Type_, visit_type_) \
-  template <> struct visit_type<Type_> { typedef visit_type_ Type; }
+#define VISIT_TYPE(type_, visit_type_) \
+  template <> struct visit_type<type_> { using type = visit_type_; }
 
 VISIT_TYPE(signed char, int);
 VISIT_TYPE(unsigned char, unsigned);
@@ -294,36 +292,34 @@
   {                                                                           \
     testing::StrictMock<mock_visitor<decltype(expected)>> visitor;            \
     EXPECT_CALL(visitor, visit(expected));                                    \
-    typedef std::back_insert_iterator<buffer<Char>> iterator;                 \
+    using iterator = std::back_insert_iterator<buffer<Char>>;                 \
     fmt::visit_format_arg(                                                    \
         visitor, make_arg<fmt::basic_format_context<iterator, Char>>(value)); \
   }
 
 #define CHECK_ARG(value, typename_)                          \
   {                                                          \
-    typedef decltype(value) value_type;                      \
-    typename_ visit_type<value_type>::Type expected = value; \
+    using value_type = decltype(value);                      \
+    typename_ visit_type<value_type>::type expected = value; \
     CHECK_ARG_(char, expected, value)                        \
     CHECK_ARG_(wchar_t, expected, value)                     \
   }
 
 template <typename T> class NumericArgTest : public testing::Test {};
 
-typedef ::testing::Types<bool, signed char, unsigned char, signed,
-                         unsigned short, int, unsigned, long, unsigned long,
-                         long long, unsigned long long, float, double,
-                         long double>
-    Types;
-TYPED_TEST_CASE(NumericArgTest, Types);
+using types =
+    ::testing::Types<bool, signed char, unsigned char, signed, unsigned short,
+                     int, unsigned, long, unsigned long, long long,
+                     unsigned long long, float, double, long double>;
+TYPED_TEST_CASE(NumericArgTest, types);
 
 template <typename T>
-typename std::enable_if<std::is_integral<T>::value, T>::type test_value() {
+fmt::enable_if_t<std::is_integral<T>::value, T> test_value() {
   return static_cast<T>(42);
 }
 
 template <typename T>
-typename std::enable_if<std::is_floating_point<T>::value, T>::type
-test_value() {
+fmt::enable_if_t<std::is_floating_point<T>::value, T> test_value() {
   return static_cast<T>(4.2);
 }
 
@@ -345,7 +341,7 @@
   const char* cstr = str;
   CHECK_ARG_(char, cstr, str);
 
-  string_view sref(str);
+  auto sref = string_view(str);
   CHECK_ARG_(char, sref, std::string(str));
 }
 
@@ -372,14 +368,14 @@
 struct check_custom {
   test_result operator()(
       fmt::basic_format_arg<fmt::format_context>::handle h) const {
-    struct test_buffer : fmt::internal::buffer<char> {
+    struct test_buffer final : fmt::detail::buffer<char> {
       char data[10];
-      test_buffer() : fmt::internal::buffer<char>(data, 0, 10) {}
-      void grow(std::size_t) {}
+      test_buffer() : fmt::detail::buffer<char>(data, 0, 10) {}
+      void grow(size_t) {}
     } buffer;
-    fmt::internal::buffer<char>& base = buffer;
     fmt::format_parse_context parse_ctx("");
-    fmt::format_context ctx(std::back_inserter(base), fmt::format_args());
+    fmt::format_context ctx{fmt::detail::buffer_appender<char>(buffer),
+                            fmt::format_args()};
     h.format(parse_ctx, ctx);
     EXPECT_EQ("test", std::string(buffer.data, buffer.size()));
     return test_result();
@@ -388,10 +384,10 @@
 
 TEST(ArgTest, CustomArg) {
   test_struct test;
-  typedef mock_visitor<fmt::basic_format_arg<fmt::format_context>::handle>
-      visitor;
+  using visitor =
+      mock_visitor<fmt::basic_format_arg<fmt::format_context>::handle>;
   testing::StrictMock<visitor> v;
-  EXPECT_CALL(v, visit(_)).WillOnce(testing::Invoke(check_custom()));
+  EXPECT_CALL(v, visit(_)).WillOnce(Invoke(check_custom()));
   fmt::visit_format_arg(v, make_arg<fmt::format_context>(test));
 }
 
@@ -402,8 +398,165 @@
   fmt::visit_format_arg(visitor, arg);
 }
 
+TEST(FormatDynArgsTest, Basic) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.push_back(42);
+  store.push_back("abc1");
+  store.push_back(1.5f);
+  EXPECT_EQ("42 and abc1 and 1.5", fmt::vformat("{} and {} and {}", store));
+}
+
+TEST(FormatDynArgsTest, StringsAndRefs) {
+  // Unfortunately the tests are compiled with old ABI so strings use COW.
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  char str[] = "1234567890";
+  store.push_back(str);
+  store.push_back(std::cref(str));
+  store.push_back(fmt::string_view{str});
+  str[0] = 'X';
+
+  std::string result = fmt::vformat("{} and {} and {}", store);
+  EXPECT_EQ("1234567890 and X234567890 and X234567890", result);
+}
+
+struct custom_type {
+  int i = 0;
+};
+
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<custom_type> {
+  auto parse(format_parse_context& ctx) const -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const custom_type& p, FormatContext& ctx) -> decltype(ctx.out()) {
+    return format_to(ctx.out(), "cust={}", p.i);
+  }
+};
+FMT_END_NAMESPACE
+
+TEST(FormatDynArgsTest, CustomFormat) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  custom_type c{};
+  store.push_back(c);
+  ++c.i;
+  store.push_back(c);
+  ++c.i;
+  store.push_back(std::cref(c));
+  ++c.i;
+  std::string result = fmt::vformat("{} and {} and {}", store);
+  EXPECT_EQ("cust=0 and cust=1 and cust=3", result);
+}
+
+TEST(FormatDynArgsTest, NamedInt) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.push_back(fmt::arg("a1", 42));
+  EXPECT_EQ("42", fmt::vformat("{a1}", store));
+}
+
+TEST(FormatDynArgsTest, NamedStrings) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  char str[]{"1234567890"};
+  store.push_back(fmt::arg("a1", str));
+  store.push_back(fmt::arg("a2", std::cref(str)));
+  str[0] = 'X';
+  EXPECT_EQ("1234567890 and X234567890", fmt::vformat("{a1} and {a2}", store));
+}
+
+TEST(FormatDynArgsTest, NamedArgByRef) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+
+  // Note: fmt::arg() constructs an object which holds a reference
+  // to its value. It's not an aggregate, so it doesn't extend the
+  // reference lifetime. As a result, it's a very bad idea passing temporary
+  // as a named argument value. Only GCC with optimization level >0
+  // complains about this.
+  //
+  // A real life usecase is when you have both name and value alive
+  // guarantee their lifetime and thus don't want them to be copied into
+  // storages.
+  int a1_val{42};
+  auto a1 = fmt::arg("a1_", a1_val);
+  store.push_back("abc");
+  store.push_back(1.5f);
+  store.push_back(std::cref(a1));
+
+  std::string result = fmt::vformat("{a1_} and {} and {} and {}", store);
+  EXPECT_EQ("42 and abc and 1.5 and 42", result);
+}
+
+TEST(FormatDynArgsTest, NamedCustomFormat) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  custom_type c{};
+  store.push_back(fmt::arg("c1", c));
+  ++c.i;
+  store.push_back(fmt::arg("c2", c));
+  ++c.i;
+  store.push_back(fmt::arg("c_ref", std::cref(c)));
+  ++c.i;
+  std::string result = fmt::vformat("{c1} and {c2} and {c_ref}", store);
+  EXPECT_EQ("cust=0 and cust=1 and cust=3", result);
+}
+
+TEST(FormatDynArgsTest, Clear) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.push_back(42);
+
+  std::string result = fmt::vformat("{}", store);
+  EXPECT_EQ("42", result);
+
+  store.push_back(43);
+  result = fmt::vformat("{} and {}", store);
+  EXPECT_EQ("42 and 43", result);
+
+  store.clear();
+  store.push_back(44);
+  result = fmt::vformat("{}", store);
+  EXPECT_EQ("44", result);
+}
+
+TEST(FormatDynArgsTest, Reserve) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.reserve(2, 1);
+  store.push_back(1.5f);
+  store.push_back(fmt::arg("a1", 42));
+  std::string result = fmt::vformat("{a1} and {}", store);
+  EXPECT_EQ("42 and 1.5", result);
+}
+
+struct copy_throwable {
+  copy_throwable() {}
+  copy_throwable(const copy_throwable&) { throw "deal with it"; }
+};
+
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<copy_throwable> {
+  auto parse(format_parse_context& ctx) const -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+  auto format(copy_throwable, format_context& ctx) -> decltype(ctx.out()) {
+    return ctx.out();
+  }
+};
+FMT_END_NAMESPACE
+
+TEST(FormatDynArgsTest, ThrowOnCopy) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.push_back(std::string("foo"));
+  try {
+    store.push_back(copy_throwable());
+  } catch (...) {
+  }
+  EXPECT_EQ(fmt::vformat("{}", store), "foo");
+}
+
+TEST(StringViewTest, ValueType) {
+  static_assert(std::is_same<string_view::value_type, char>::value, "");
+}
+
 TEST(StringViewTest, Length) {
-  // Test that StringRef::size() returns string length, not buffer size.
+  // Test that string_view::size() returns string length, not buffer size.
   char str[100] = "some string";
   EXPECT_EQ(std::strlen(str), string_view(str).size());
   EXPECT_LT(std::strlen(str), sizeof(str));
@@ -412,9 +565,9 @@
 // Check string_view's comparison operator.
 template <template <typename> class Op> void check_op() {
   const char* inputs[] = {"foo", "fop", "fo"};
-  std::size_t num_inputs = sizeof(inputs) / sizeof(*inputs);
-  for (std::size_t i = 0; i < num_inputs; ++i) {
-    for (std::size_t j = 0; j < num_inputs; ++j) {
+  size_t num_inputs = sizeof(inputs) / sizeof(*inputs);
+  for (size_t i = 0; i < num_inputs; ++i) {
+    for (size_t j = 0; j < num_inputs; ++j) {
       string_view lhs(inputs[i]), rhs(inputs[j]);
       EXPECT_EQ(Op<int>()(lhs.compare(rhs), 0), Op<string_view>()(lhs, rhs));
     }
@@ -457,13 +610,18 @@
   using context = fmt::format_context;
   static_assert(has_formatter<enabled_formatter, context>::value, "");
   static_assert(!has_formatter<disabled_formatter, context>::value, "");
-  static_assert(!has_formatter<disabled_formatter_convertible, context>::value, "");
+  static_assert(!has_formatter<disabled_formatter_convertible, context>::value,
+                "");
 }
 
 struct convertible_to_int {
   operator int() const { return 42; }
 };
 
+struct convertible_to_c_string {
+  operator const char*() const { return "foo"; }
+};
+
 FMT_BEGIN_NAMESPACE
 template <> struct formatter<convertible_to_int> {
   auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
@@ -473,22 +631,33 @@
     return std::copy_n("foo", 3, ctx.out());
   }
 };
+
+template <> struct formatter<convertible_to_c_string> {
+  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+  auto format(convertible_to_c_string, format_context& ctx)
+      -> decltype(ctx.out()) {
+    return std::copy_n("bar", 3, ctx.out());
+  }
+};
 FMT_END_NAMESPACE
 
 TEST(CoreTest, FormatterOverridesImplicitConversion) {
   EXPECT_EQ(fmt::format("{}", convertible_to_int()), "foo");
+  EXPECT_EQ(fmt::format("{}", convertible_to_c_string()), "bar");
 }
 
 namespace my_ns {
 template <typename Char> class my_string {
+ private:
+  std::basic_string<Char> s_;
+
  public:
   my_string(const Char* s) : s_(s) {}
   const Char* data() const FMT_NOEXCEPT { return s_.data(); }
-  std::size_t length() const FMT_NOEXCEPT { return s_.size(); }
+  size_t length() const FMT_NOEXCEPT { return s_.size(); }
   operator const Char*() const { return s_.c_str(); }
-
- private:
-  std::basic_string<Char> s_;
 };
 
 template <typename Char>
@@ -500,23 +669,6 @@
 struct non_string {};
 }  // namespace my_ns
 
-namespace FakeQt {
-class QString {
- public:
-  QString(const wchar_t* s) : s_(std::make_shared<std::wstring>(s)) {}
-  const wchar_t* utf16() const FMT_NOEXCEPT { return s_->data(); }
-  int size() const FMT_NOEXCEPT { return static_cast<int>(s_->size()); }
-
- private:
-  std::shared_ptr<std::wstring> s_;
-};
-
-inline fmt::basic_string_view<wchar_t> to_string_view(const QString& s)
-    FMT_NOEXCEPT {
-  return {s.utf16(), static_cast<std::size_t>(s.size())};
-}
-}  // namespace FakeQt
-
 template <typename T> class IsStringTest : public testing::Test {};
 
 typedef ::testing::Types<char, wchar_t, char16_t, char32_t> StringCharTypes;
@@ -528,21 +680,19 @@
 }  // namespace
 
 TYPED_TEST(IsStringTest, IsString) {
-  EXPECT_TRUE(fmt::internal::is_string<TypeParam*>::value);
-  EXPECT_TRUE(fmt::internal::is_string<const TypeParam*>::value);
-  EXPECT_TRUE(fmt::internal::is_string<TypeParam[2]>::value);
-  EXPECT_TRUE(fmt::internal::is_string<const TypeParam[2]>::value);
-  EXPECT_TRUE(fmt::internal::is_string<std::basic_string<TypeParam>>::value);
+  EXPECT_TRUE(fmt::detail::is_string<TypeParam*>::value);
+  EXPECT_TRUE(fmt::detail::is_string<const TypeParam*>::value);
+  EXPECT_TRUE(fmt::detail::is_string<TypeParam[2]>::value);
+  EXPECT_TRUE(fmt::detail::is_string<const TypeParam[2]>::value);
+  EXPECT_TRUE(fmt::detail::is_string<std::basic_string<TypeParam>>::value);
+  EXPECT_TRUE(fmt::detail::is_string<fmt::basic_string_view<TypeParam>>::value);
   EXPECT_TRUE(
-      fmt::internal::is_string<fmt::basic_string_view<TypeParam>>::value);
-  EXPECT_TRUE(
-      fmt::internal::is_string<derived_from_string_view<TypeParam>>::value);
-  using string_view = fmt::internal::std_string_view<TypeParam>;
+      fmt::detail::is_string<derived_from_string_view<TypeParam>>::value);
+  using string_view = fmt::detail::std_string_view<TypeParam>;
   EXPECT_TRUE(std::is_empty<string_view>::value !=
-              fmt::internal::is_string<string_view>::value);
-  EXPECT_TRUE(fmt::internal::is_string<my_ns::my_string<TypeParam>>::value);
-  EXPECT_FALSE(fmt::internal::is_string<my_ns::non_string>::value);
-  EXPECT_TRUE(fmt::internal::is_string<FakeQt::QString>::value);
+              fmt::detail::is_string<string_view>::value);
+  EXPECT_TRUE(fmt::detail::is_string<my_ns::my_string<TypeParam>>::value);
+  EXPECT_FALSE(fmt::detail::is_string<my_ns::non_string>::value);
 }
 
 TEST(CoreTest, Format) {
@@ -565,33 +715,16 @@
 
 TEST(CoreTest, ToStringViewForeignStrings) {
   using namespace my_ns;
-  using namespace FakeQt;
   EXPECT_EQ(to_string_view(my_string<char>("42")), "42");
-  EXPECT_EQ(to_string_view(my_string<wchar_t>(L"42")), L"42");
-  EXPECT_EQ(to_string_view(QString(L"42")), L"42");
-  fmt::internal::type type =
-      fmt::internal::mapped_type_constant<my_string<char>,
-                                          fmt::format_context>::value;
-  EXPECT_EQ(type, fmt::internal::string_type);
-  type = fmt::internal::mapped_type_constant<my_string<wchar_t>,
-                                             fmt::wformat_context>::value;
-  EXPECT_EQ(type, fmt::internal::string_type);
-  type =
-      fmt::internal::mapped_type_constant<QString, fmt::wformat_context>::value;
-  EXPECT_EQ(type, fmt::internal::string_type);
-  // Does not compile: only wide format contexts are compatible with QString!
-  // type = fmt::internal::mapped_type_constant<QString,
-  // fmt::format_context>::value;
+  fmt::detail::type type =
+      fmt::detail::mapped_type_constant<my_string<char>,
+                                        fmt::format_context>::value;
+  EXPECT_EQ(type, fmt::detail::type::string_type);
 }
 
 TEST(CoreTest, FormatForeignStrings) {
   using namespace my_ns;
-  using namespace FakeQt;
   EXPECT_EQ(fmt::format(my_string<char>("{}"), 42), "42");
-  EXPECT_EQ(fmt::format(my_string<wchar_t>(L"{}"), 42), L"42");
-  EXPECT_EQ(fmt::format(QString(L"{}"), 42), L"42");
-  EXPECT_EQ(fmt::format(QString(L"{}"), my_string<wchar_t>(L"42")), L"42");
-  EXPECT_EQ(fmt::format(my_string<wchar_t>(L"{}"), QString(L"42")), L"42");
 }
 
 struct implicitly_convertible_to_string {
@@ -602,7 +735,7 @@
   operator fmt::string_view() const { return "foo"; }
 };
 
-TEST(FormatterTest, FormatImplicitlyConvertibleToStringView) {
+TEST(CoreTest, FormatImplicitlyConvertibleToStringView) {
   EXPECT_EQ("foo", fmt::format("{}", implicitly_convertible_to_string_view()));
 }
 
@@ -612,38 +745,29 @@
   explicit operator fmt::string_view() const { return "foo"; }
 };
 
-TEST(FormatterTest, FormatExplicitlyConvertibleToStringView) {
+TEST(CoreTest, FormatExplicitlyConvertibleToStringView) {
   EXPECT_EQ("foo", fmt::format("{}", explicitly_convertible_to_string_view()));
 }
 
-#ifdef FMT_USE_STRING_VIEW
+#  ifdef FMT_USE_STRING_VIEW
 struct explicitly_convertible_to_std_string_view {
   explicit operator std::string_view() const { return "foo"; }
 };
 
-TEST(FormatterTest, FormatExplicitlyConvertibleToStdStringView) {
+TEST(CoreTest, FormatExplicitlyConvertibleToStdStringView) {
   EXPECT_EQ("foo",
             fmt::format("{}", explicitly_convertible_to_std_string_view()));
 }
-#endif
-
-struct explicitly_convertible_to_wstring_view {
-  explicit operator fmt::wstring_view() const { return L"foo"; }
-};
-
-TEST(FormatterTest, FormatExplicitlyConvertibleToWStringView) {
-  EXPECT_EQ(L"foo",
-            fmt::format(L"{}", explicitly_convertible_to_wstring_view()));
-}
+#  endif
 #endif
 
 struct disabled_rvalue_conversion {
   operator const char*() const& { return "foo"; }
-  operator const char*()& { return "foo"; }
+  operator const char*() & { return "foo"; }
   operator const char*() const&& = delete;
-  operator const char*()&& = delete;
+  operator const char*() && = delete;
 };
 
-TEST(FormatterTest, DisabledRValueConversion) {
+TEST(CoreTest, DisabledRValueConversion) {
   EXPECT_EQ("foo", fmt::format("{}", disabled_rvalue_conversion()));
 }
diff --git a/test/custom-formatter-test.cc b/test/custom-formatter-test.cc
deleted file mode 100644
index 36007ca..0000000
--- a/test/custom-formatter-test.cc
+++ /dev/null
@@ -1,56 +0,0 @@
-// Formatting library for C++ - custom argument formatter tests
-//
-// Copyright (c) 2012 - present, Victor Zverovich
-// All rights reserved.
-//
-// For the license information refer to format.h.
-
-#ifndef _CRT_SECURE_NO_WARNINGS
-#define _CRT_SECURE_NO_WARNINGS
-#endif
-
-#include "fmt/format.h"
-#include "gtest-extra.h"
-
-// MSVC 2013 is known to be broken.
-#if !FMT_MSC_VER || FMT_MSC_VER > 1800
-
-// A custom argument formatter that doesn't print `-` for floating-point values
-// rounded to 0.
-class custom_arg_formatter
-    : public fmt::arg_formatter<fmt::buffer_range<char>> {
- public:
-  using range = fmt::buffer_range<char>;
-  typedef fmt::arg_formatter<range> base;
-
-  custom_arg_formatter(fmt::format_context& ctx,
-                       fmt::format_parse_context* parse_ctx,
-                       fmt::format_specs* s = nullptr)
-      : base(ctx, parse_ctx, s) {}
-
-  using base::operator();
-
-  iterator operator()(double value) {
-    // Comparing a float to 0.0 is safe.
-    if (round(value * pow(10, specs()->precision)) == 0.0) value = 0;
-    return base::operator()(value);
-  }
-};
-
-std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
-  fmt::memory_buffer buffer;
-  // Pass custom argument formatter as a template arg to vwrite.
-  fmt::vformat_to<custom_arg_formatter>(buffer, format_str, args);
-  return std::string(buffer.data(), buffer.size());
-}
-
-template <typename... Args>
-std::string custom_format(const char* format_str, const Args&... args) {
-  auto va = fmt::make_format_args(args...);
-  return custom_vformat(format_str, va);
-}
-
-TEST(CustomFormatterTest, Format) {
-  EXPECT_EQ("0.00", custom_format("{:.2f}", -.00001));
-}
-#endif
diff --git a/test/find-package-test/CMakeLists.txt b/test/find-package-test/CMakeLists.txt
index 5135755..93d686e 100644
--- a/test/find-package-test/CMakeLists.txt
+++ b/test/find-package-test/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1.0)
+cmake_minimum_required(VERSION 3.1...3.18)
 
 project(fmt-test)
 
diff --git a/test/format b/test/format
index db27614..76ac547 100644
--- a/test/format
+++ b/test/format
@@ -38,9 +38,9 @@
   
   template<class Out, class charT> class basic_format_context;
   using format_context = basic_format_context<
-    /* unspecified */ std::back_insert_iterator<fmt::internal::buffer<char>>, char>;
+    /* unspecified */ fmt::detail::buffer_appender<char>, char>;
   using wformat_context = basic_format_context<
-    /* unspecified */ std::back_insert_iterator<fmt::internal::buffer<wchar_t>>, wchar_t>;
+    /* unspecified */ fmt::detail::buffer_appender<wchar_t>, wchar_t>;
 
   template<class T, class charT = char> struct formatter {
     formatter() = delete;
@@ -83,9 +83,9 @@
     Out format_to(Out out, wstring_view fmt, const Args&... args);
 
   template<class Out>
-    Out vformat_to(Out out, string_view fmt, format_args_t<Out, char> args);
+    Out vformat_to(Out out, string_view fmt, format_args_t<fmt::type_identity_t<Out>, char> args);
   template<class Out>
-    Out vformat_to(Out out, wstring_view fmt, format_args_t<Out, wchar_t> args);
+    Out vformat_to(Out out, wstring_view fmt, format_args_t<fmt::type_identity_t<Out>, wchar_t> args);
 
   template<class Out>
     struct format_to_n_result {
@@ -219,7 +219,7 @@
 
     // Implementation details:
     using format_arg = basic_format_arg<basic_format_context>;
-    basic_format_context(Out out, basic_format_args<basic_format_context> args, fmt::internal::locale_ref)
+    basic_format_context(Out out, basic_format_args<basic_format_context> args, fmt::detail::locale_ref)
     : args_(args), out_(out) {}
     detail::error_handler error_handler() const { return {}; }
     basic_format_arg<basic_format_context> arg(fmt::basic_string_view<charT>) const {
@@ -488,22 +488,21 @@
 namespace std {
 namespace detail {
 
-template <typename Range>
+template <typename OutputIt, typename Char>
 class arg_formatter
-    : public fmt::internal::arg_formatter_base<Range, error_handler> {
+    : public fmt::detail::arg_formatter_base<OutputIt, Char, error_handler> {
  private:
-  using char_type = typename Range::value_type;
-  using base = fmt::internal::arg_formatter_base<Range, error_handler>;
-  using format_context = std::basic_format_context<typename base::iterator, char_type>;
-  using parse_context = basic_format_parse_context<char_type>;
+  using char_type = Char;
+  using base = fmt::detail::arg_formatter_base<OutputIt, Char, error_handler>;
+  using format_context = std::basic_format_context<OutputIt, Char>;
+  using parse_context = basic_format_parse_context<Char>;
 
   parse_context* parse_ctx_;
   format_context& ctx_;
 
  public:
-  typedef Range range;
-  typedef typename base::iterator iterator;
-  typedef typename base::format_specs format_specs;
+  using iterator = OutputIt;
+  using format_specs = typename base::format_specs;
 
   /**
     \rst
@@ -513,7 +512,7 @@
     \endrst
    */
   arg_formatter(format_context& ctx, parse_context* parse_ctx = nullptr, fmt::format_specs* spec = nullptr)
-      : base(Range(ctx.out()), spec, {}), parse_ctx_(parse_ctx), ctx_(ctx) {}
+      : base(ctx.out(), spec, {}), parse_ctx_(parse_ctx), ctx_(ctx) {}
 
   using base::operator();
 
@@ -529,36 +528,36 @@
 };
 
 template <typename Context>
-inline fmt::internal::type get_type(basic_format_arg<Context> arg) {
+inline fmt::detail::type get_type(basic_format_arg<Context> arg) {
   return visit_format_arg([&] (auto val) {
     using char_type = typename Context::char_type;
     using T = decltype(val);
     if (std::is_same_v<T, monostate>)
-      return fmt::internal::none_type;
+      return fmt::detail::type::none_type;
     if (std::is_same_v<T, bool>)
-      return fmt::internal::bool_type;
+      return fmt::detail::type::bool_type;
     if (std::is_same_v<T, char_type>)
-      return fmt::internal::char_type;
+      return fmt::detail::type::char_type;
     if (std::is_same_v<T, int>)
-      return fmt::internal::int_type;
+      return fmt::detail::type::int_type;
     if (std::is_same_v<T, unsigned int>)
-      return fmt::internal::uint_type;
+      return fmt::detail::type::uint_type;
     if (std::is_same_v<T, long long int>)
-      return fmt::internal::long_long_type;
+      return fmt::detail::type::long_long_type;
     if (std::is_same_v<T, unsigned long long int>)
-      return fmt::internal::ulong_long_type;
+      return fmt::detail::type::ulong_long_type;
     if (std::is_same_v<T, double>)
-      return fmt::internal::double_type;
+      return fmt::detail::type::double_type;
     if (std::is_same_v<T, long double>)
-      return fmt::internal::long_double_type;
+      return fmt::detail::type::long_double_type;
     if (std::is_same_v<T, const char_type*>)
-      return fmt::internal::cstring_type;
+      return fmt::detail::type::cstring_type;
     if (std::is_same_v<T, basic_string_view<char_type>>)
-      return fmt::internal::string_type;
+      return fmt::detail::type::string_type;
     if (std::is_same_v<T, const void*>)
-      return fmt::internal::pointer_type;
+      return fmt::detail::type::pointer_type;
     assert(get_value(arg).index() == 12);
-    return fmt::internal::custom_type;
+    return fmt::detail::type::custom_type;
   }, arg);
 }
 
@@ -582,45 +581,42 @@
 
 template <typename ArgFormatter, typename Char, typename Context>
 struct format_handler : detail::error_handler {
-  typedef typename ArgFormatter::range range;
+  using iterator = typename ArgFormatter::iterator;
 
-  format_handler(range r, basic_string_view<Char> str,
+  format_handler(iterator out, basic_string_view<Char> str,
                  basic_format_args<Context> format_args,
-                 fmt::internal::locale_ref loc)
-      : parse_ctx(str), context(r.begin(), format_args, loc) {}
+                 fmt::detail::locale_ref loc)
+      : parse_ctx(str), context(out, format_args, loc) {}
 
   void on_text(const Char* begin, const Char* end) {
-    auto size = fmt::internal::to_unsigned(end - begin);
+    auto size = fmt::detail::to_unsigned(end - begin);
     auto out = context.out();
-    auto&& it = fmt::internal::reserve(out, size);
+    auto&& it = fmt::detail::reserve(out, size);
     it = std::copy_n(begin, size, it);
     context.advance_to(out);
   }
 
-  void on_arg_id() {
-    arg = context.arg(parse_ctx.next_arg_id());
-  }
-  void on_arg_id(unsigned id) {
-    parse_ctx.check_arg_id(id);
-    arg = context.arg(id);
-  }
-  void on_arg_id(fmt::basic_string_view<Char>) {}
+  int on_arg_id() { return parse_ctx.next_arg_id(); }
+  int on_arg_id(unsigned id) { return parse_ctx.check_arg_id(id), id; }
+  int on_arg_id(fmt::basic_string_view<Char>) { return 0; }
 
-  void on_replacement_field(const Char* p) {
-    parse_ctx.advance_to(parse_ctx.begin() + (p - &*parse_ctx.begin()));
+  void on_replacement_field(int id, const Char* p) {
+    auto arg = context.arg(id);
+    parse_ctx.advance_to(parse_ctx.begin() + (p  - &*parse_ctx.begin()));
     custom_formatter<Context> f(parse_ctx, context);
     if (!visit_format_arg(f, arg))
       context.advance_to(visit_format_arg(ArgFormatter(context, &parse_ctx), arg));
   }
 
-  const Char* on_format_specs(const Char* begin, const Char* end) {
+  const Char* on_format_specs(int id, const Char* begin, const Char* end) {
+    auto arg = context.arg(id);
     parse_ctx.advance_to(parse_ctx.begin() + (begin - &*parse_ctx.begin()));
     custom_formatter<Context> f(parse_ctx, context);
     if (visit_format_arg(f, arg)) return &*parse_ctx.begin();
     fmt::basic_format_specs<Char> specs;
-    using fmt::internal::specs_handler;
+    using fmt::detail::specs_handler;
     using parse_context = basic_format_parse_context<Char>;
-    fmt::internal::specs_checker<specs_handler<parse_context, Context>> handler(
+    fmt::detail::specs_checker<specs_handler<parse_context, Context>> handler(
         specs_handler<parse_context, Context>(specs, parse_ctx, context), get_type(arg));
     begin = parse_format_specs(begin, end, handler);
     if (begin == end || *begin != '}') on_error("missing '}' in format string");
@@ -631,7 +627,6 @@
 
   basic_format_parse_context<Char> parse_ctx;
   Context context;
-  basic_format_arg<Context> arg;
 };
 
 template <typename T, typename Char>
@@ -640,46 +635,45 @@
   // terminating '}'.
   template <typename ParseContext>
   FMT_CONSTEXPR typename ParseContext::iterator parse(ParseContext& ctx) {
-    namespace internal = fmt::internal;
-    typedef internal::dynamic_specs_handler<ParseContext> handler_type;
-    auto type = internal::mapped_type_constant<T, fmt::buffer_context<Char>>::value;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+    namespace detail = fmt::detail;
+    typedef detail::dynamic_specs_handler<ParseContext> handler_type;
+    auto type = detail::mapped_type_constant<T, fmt::buffer_context<Char>>::value;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
                                                   type);
     auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
     auto type_spec = specs_.type;
     auto eh = ctx.error_handler();
     switch (type) {
-    case internal::none_type:
-    case internal::named_arg_type:
+    case detail::type::none_type:
       FMT_ASSERT(false, "invalid argument type");
       break;
-    case internal::int_type:
-    case internal::uint_type:
-    case internal::long_long_type:
-    case internal::ulong_long_type:
-    case internal::bool_type:
+    case detail::type::int_type:
+    case detail::type::uint_type:
+    case detail::type::long_long_type:
+    case detail::type::ulong_long_type:
+    case detail::type::bool_type:
       handle_int_type_spec(type_spec,
-                           internal::int_type_checker<decltype(eh)>(eh));
+                           detail::int_type_checker<decltype(eh)>(eh));
       break;
-    case internal::char_type:
+    case detail::type::char_type:
       handle_char_specs(
-          &specs_, internal::char_specs_checker<decltype(eh)>(type_spec, eh));
+          &specs_, detail::char_specs_checker<decltype(eh)>(type_spec, eh));
       break;
-    case internal::double_type:
-    case internal::long_double_type:
-      internal::parse_float_type_spec(specs_, eh);
+    case detail::type::double_type:
+    case detail::type::long_double_type:
+      detail::parse_float_type_spec(specs_, eh);
       break;
-    case internal::cstring_type:
-      internal::handle_cstring_type_spec(
-          type_spec, internal::cstring_type_checker<decltype(eh)>(eh));
+    case detail::type::cstring_type:
+      detail::handle_cstring_type_spec(
+          type_spec, detail::cstring_type_checker<decltype(eh)>(eh));
       break;
-    case internal::string_type:
-      internal::check_string_type_spec(type_spec, eh);
+    case detail::type::string_type:
+      detail::check_string_type_spec(type_spec, eh);
       break;
-    case internal::pointer_type:
-      internal::check_pointer_type_spec(type_spec, eh);
+    case detail::type::pointer_type:
+      detail::check_pointer_type_spec(type_spec, eh);
       break;
-    case internal::custom_type:
+    case detail::type::custom_type:
       // Custom format specifiers should be checked in parse functions of
       // formatter specializations.
       break;
@@ -689,18 +683,18 @@
 
   template <typename FormatContext>
   auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
-    fmt::internal::handle_dynamic_spec<fmt::internal::width_checker>(
+    fmt::detail::handle_dynamic_spec<fmt::detail::width_checker>(
         specs_.width, specs_.width_ref, ctx);
-    fmt::internal::handle_dynamic_spec<fmt::internal::precision_checker>(
+    fmt::detail::handle_dynamic_spec<fmt::detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
-    using range_type = fmt::internal::output_range<typename FormatContext::iterator,
-                         typename FormatContext::char_type>;
-    return visit_format_arg(arg_formatter<range_type>(ctx, nullptr, &specs_),
+    using af = arg_formatter<typename FormatContext::iterator,
+                             typename FormatContext::char_type>;
+    return visit_format_arg(af(ctx, nullptr, &specs_),
                             basic_format_arg<FormatContext>(val));
   }
 
  private:
-  fmt::internal::dynamic_format_specs<Char> specs_;
+  fmt::detail::dynamic_format_specs<Char> specs_;
 };
 }  // namespace detail
 
@@ -717,11 +711,11 @@
 
 string vformat(string_view fmt, format_args args) {
   fmt::memory_buffer mbuf;
-  fmt::internal::buffer<char>& buf = mbuf;
-  using range = fmt::buffer_range<char>;
-  detail::format_handler<detail::arg_formatter<range>, char, format_context>
-    h(range(std::back_inserter(buf)), fmt, args, {});
-  fmt::internal::parse_format_string<false>(fmt::to_string_view(fmt), h);
+  fmt::detail::buffer<char>& buf = mbuf;
+  using af = detail::arg_formatter<fmt::format_context::iterator, char>;
+  detail::format_handler<af, char, format_context>
+    h(fmt::detail::buffer_appender<char>(buf), fmt, args, {});
+  fmt::detail::parse_format_string<false>(fmt::to_string_view(fmt), h);
   return to_string(mbuf);
 }
 
@@ -730,26 +724,26 @@
 template<class Out, class... Args>
   Out format_to(Out out, string_view fmt, const Args&... args) {
     using context = basic_format_context<Out, decltype(fmt)::value_type>;
-    return vformat_to(out, fmt, {make_format_args<context>(args...)});
+    return vformat_to(out, fmt, make_format_args<context>(args...));
   }
 
 template<class Out, class... Args>
   Out format_to(Out out, wstring_view fmt, const Args&... args) {
     using context = basic_format_context<Out, decltype(fmt)::value_type>;
-    return vformat_to(out, fmt, {make_format_args<context>(args...)});
+    return vformat_to(out, fmt, make_format_args<context>(args...));
   }
 
 template<class Out>
-  Out vformat_to(Out out, string_view fmt, format_args_t<Out, char> args) {
-    using range = fmt::internal::output_range<Out, char>;
-    detail::format_handler<detail::arg_formatter<range>, char, basic_format_context<Out, char>>
-      h(range(out), fmt, args, {});
-    fmt::internal::parse_format_string<false>(fmt::to_string_view(fmt), h);
+  Out vformat_to(Out out, string_view fmt, format_args_t<fmt::type_identity_t<Out>, char> args) {
+    using af = detail::arg_formatter<Out, char>;
+    detail::format_handler<af, char, basic_format_context<Out, char>>
+      h(out, fmt, args, {});
+    fmt::detail::parse_format_string<false>(fmt::to_string_view(fmt), h);
     return h.context.out();
   }
 
 template<class Out>
-  Out vformat_to(Out out, wstring_view fmt, format_args_t<Out, wchar_t> args);
+  Out vformat_to(Out out, wstring_view fmt, format_args_t<fmt::type_identity_t<Out>, wchar_t> args);
 
 template<class Out, class... Args>
   format_to_n_result<Out> format_to_n(Out out, iter_difference_t<Out> n,
diff --git a/test/format-impl-test.cc b/test/format-impl-test.cc
index 3c94438..1290c07 100644
--- a/test/format-impl-test.cc
+++ b/test/format-impl-test.cc
@@ -10,21 +10,23 @@
 #include "test-assert.h"
 
 // Include format.cc instead of format.h to test implementation.
-#include "../src/format.cc"
-#include "fmt/printf.h"
-
 #include <algorithm>
 #include <cstring>
 
+#include "../src/format.cc"
+#include "fmt/printf.h"
 #include "gmock.h"
 #include "gtest-extra.h"
 #include "util.h"
 
-#undef max
+#ifdef _WIN32
+#  include <windows.h>
+#  undef max
+#endif
 
-using fmt::internal::bigint;
-using fmt::internal::fp;
-using fmt::internal::max_value;
+using fmt::detail::bigint;
+using fmt::detail::fp;
+using fmt::detail::max_value;
 
 static_assert(!std::is_copy_constructible<bigint>::value, "");
 static_assert(!std::is_copy_assignable<bigint>::value, "");
@@ -103,7 +105,7 @@
 }
 
 TEST(BigIntTest, Accumulator) {
-  fmt::internal::accumulator acc;
+  fmt::detail::accumulator acc;
   EXPECT_EQ(acc.lower, 0);
   EXPECT_EQ(acc.upper, 0);
   acc.upper = 12;
@@ -111,7 +113,7 @@
   EXPECT_EQ(static_cast<uint32_t>(acc), 34);
   acc += 56;
   EXPECT_EQ(acc.lower, 90);
-  acc += fmt::internal::max_value<uint64_t>();
+  acc += fmt::detail::max_value<uint64_t>();
   EXPECT_EQ(acc.upper, 13);
   EXPECT_EQ(acc.lower, 89);
   acc >>= 32;
@@ -187,29 +189,6 @@
 template <> void run_double_tests<true>() {
   // Construct from double.
   EXPECT_EQ(fp(1.23), fp(0x13ae147ae147aeu, -52));
-
-  // Compute boundaries:
-  fp value;
-  // Normalized & not power of 2 - equidistant boundaries:
-  auto b = value.assign_with_boundaries(1.23);
-  EXPECT_EQ(value, fp(0x0013ae147ae147ae, -52));
-  EXPECT_EQ(b.lower, 0x9d70a3d70a3d6c00);
-  EXPECT_EQ(b.upper, 0x9d70a3d70a3d7400);
-  // Normalized power of 2 - lower boundary is closer:
-  b = value.assign_with_boundaries(1.9807040628566084e+28);  // 2**94
-  EXPECT_EQ(value, fp(0x0010000000000000, 42));
-  EXPECT_EQ(b.lower, 0x7ffffffffffffe00);
-  EXPECT_EQ(b.upper, 0x8000000000000400);
-  // Smallest normalized double - equidistant boundaries:
-  b = value.assign_with_boundaries(2.2250738585072014e-308);
-  EXPECT_EQ(value, fp(0x0010000000000000, -1074));
-  EXPECT_EQ(b.lower, 0x7ffffffffffffc00);
-  EXPECT_EQ(b.upper, 0x8000000000000400);
-  // Subnormal - equidistant boundaries:
-  b = value.assign_with_boundaries(4.9406564584124654e-324);
-  EXPECT_EQ(value, fp(0x0000000000000001, -1074));
-  EXPECT_EQ(b.lower, 0x4000000000000000);
-  EXPECT_EQ(b.upper, 0xc000000000000000);
 }
 
 TEST(FPTest, DoubleTests) {
@@ -223,33 +202,6 @@
   EXPECT_EQ(-6, normalized.e);
 }
 
-TEST(FPTest, ComputeFloatBoundaries) {
-  struct {
-    double x, lower, upper;
-  } tests[] = {
-      // regular
-      {1.5f, 1.4999999403953552, 1.5000000596046448},
-      // boundary
-      {1.0f, 0.9999999701976776, 1.0000000596046448},
-      // min normal
-      {1.1754944e-38f, 1.1754942807573643e-38, 1.1754944208872107e-38},
-      // max subnormal
-      {1.1754942e-38f, 1.1754941406275179e-38, 1.1754942807573643e-38},
-      // min subnormal
-      {1e-45f, 7.006492321624085e-46, 2.1019476964872256e-45},
-  };
-  for (auto test : tests) {
-    fp vlower = normalize(fp(test.lower));
-    fp vupper = normalize(fp(test.upper));
-    vlower.f >>= vupper.e - vlower.e;
-    vlower.e = vupper.e;
-    fp value;
-    auto b = value.assign_float_with_boundaries(test.x);
-    EXPECT_EQ(vlower.f, b.lower);
-    EXPECT_EQ(vupper.f, b.upper);
-  }
-}
-
 TEST(FPTest, Multiply) {
   auto v = fp(123ULL << 32, 4) * fp(56ULL << 32, 7);
   EXPECT_EQ(v.f, 123u * 56u);
@@ -260,44 +212,83 @@
 }
 
 TEST(FPTest, GetCachedPower) {
-  typedef std::numeric_limits<double> limits;
+  using limits = std::numeric_limits<double>;
   for (auto exp = limits::min_exponent; exp <= limits::max_exponent; ++exp) {
     int dec_exp = 0;
-    auto fp = fmt::internal::get_cached_power(exp, dec_exp);
-    EXPECT_LE(exp, fp.e);
-    int dec_exp_step = 8;
-    EXPECT_LE(fp.e, exp + dec_exp_step * log2(10));
-    EXPECT_DOUBLE_EQ(pow(10, dec_exp), ldexp(static_cast<double>(fp.f), fp.e));
+    auto fp = fmt::detail::get_cached_power(exp, dec_exp);
+    bigint exact, cache(fp.f);
+    if (dec_exp >= 0) {
+      exact.assign_pow10(dec_exp);
+      if (fp.e <= 0)
+        exact <<= -fp.e;
+      else
+        cache <<= fp.e;
+      exact.align(cache);
+      cache.align(exact);
+      auto exact_str = fmt::format("{}", exact);
+      auto cache_str = fmt::format("{}", cache);
+      EXPECT_EQ(exact_str.size(), cache_str.size());
+      EXPECT_EQ(exact_str.substr(0, 15), cache_str.substr(0, 15));
+      int diff = cache_str[15] - exact_str[15];
+      if (diff == 1)
+        EXPECT_GT(exact_str[16], '8');
+      else
+        EXPECT_EQ(diff, 0);
+    } else {
+      cache.assign_pow10(-dec_exp);
+      cache *= fp.f + 1;  // Inexact check.
+      exact.assign(1);
+      exact <<= -fp.e;
+      exact.align(cache);
+      auto exact_str = fmt::format("{}", exact);
+      auto cache_str = fmt::format("{}", cache);
+      EXPECT_EQ(exact_str.size(), cache_str.size());
+      EXPECT_EQ(exact_str.substr(0, 16), cache_str.substr(0, 16));
+    }
   }
 }
 
+TEST(FPTest, DragonboxMaxK) {
+  using fmt::detail::dragonbox::floor_log10_pow2;
+  using float_info = fmt::detail::dragonbox::float_info<float>;
+  EXPECT_EQ(fmt::detail::const_check(float_info::max_k),
+            float_info::kappa - floor_log10_pow2(float_info::min_exponent -
+                                                 float_info::significand_bits));
+  using double_info = fmt::detail::dragonbox::float_info<double>;
+  EXPECT_EQ(
+      fmt::detail::const_check(double_info::max_k),
+      double_info::kappa - floor_log10_pow2(double_info::min_exponent -
+                                            double_info::significand_bits));
+}
+
 TEST(FPTest, GetRoundDirection) {
-  using fmt::internal::get_round_direction;
-  EXPECT_EQ(fmt::internal::down, get_round_direction(100, 50, 0));
-  EXPECT_EQ(fmt::internal::up, get_round_direction(100, 51, 0));
-  EXPECT_EQ(fmt::internal::down, get_round_direction(100, 40, 10));
-  EXPECT_EQ(fmt::internal::up, get_round_direction(100, 60, 10));
-  for (int i = 41; i < 60; ++i)
-    EXPECT_EQ(fmt::internal::unknown, get_round_direction(100, i, 10));
+  using fmt::detail::get_round_direction;
+  using fmt::detail::round_direction;
+  EXPECT_EQ(round_direction::down, get_round_direction(100, 50, 0));
+  EXPECT_EQ(round_direction::up, get_round_direction(100, 51, 0));
+  EXPECT_EQ(round_direction::down, get_round_direction(100, 40, 10));
+  EXPECT_EQ(round_direction::up, get_round_direction(100, 60, 10));
+  for (size_t i = 41; i < 60; ++i)
+    EXPECT_EQ(round_direction::unknown, get_round_direction(100, i, 10));
   uint64_t max = max_value<uint64_t>();
   EXPECT_THROW(get_round_direction(100, 100, 0), assertion_failure);
   EXPECT_THROW(get_round_direction(100, 0, 100), assertion_failure);
   EXPECT_THROW(get_round_direction(100, 0, 50), assertion_failure);
   // Check that remainder + error doesn't overflow.
-  EXPECT_EQ(fmt::internal::up, get_round_direction(max, max - 1, 2));
+  EXPECT_EQ(round_direction::up, get_round_direction(max, max - 1, 2));
   // Check that 2 * (remainder + error) doesn't overflow.
-  EXPECT_EQ(fmt::internal::unknown,
+  EXPECT_EQ(round_direction::unknown,
             get_round_direction(max, max / 2 + 1, max / 2));
   // Check that remainder - error doesn't overflow.
-  EXPECT_EQ(fmt::internal::unknown, get_round_direction(100, 40, 41));
+  EXPECT_EQ(round_direction::unknown, get_round_direction(100, 40, 41));
   // Check that 2 * (remainder - error) doesn't overflow.
-  EXPECT_EQ(fmt::internal::up, get_round_direction(max, max - 1, 1));
+  EXPECT_EQ(round_direction::up, get_round_direction(max, max - 1, 1));
 }
 
 TEST(FPTest, FixedHandler) {
-  struct handler : fmt::internal::fixed_handler {
+  struct handler : fmt::detail::fixed_handler {
     char buffer[10];
-    handler(int prec = 0) : fmt::internal::fixed_handler() {
+    handler(int prec = 0) : fmt::detail::fixed_handler() {
       buf = buffer;
       precision = prec;
     }
@@ -306,8 +297,8 @@
   handler().on_digit('0', 100, 99, 0, exp, false);
   EXPECT_THROW(handler().on_digit('0', 100, 100, 0, exp, false),
                assertion_failure);
-  namespace digits = fmt::internal::digits;
-  EXPECT_EQ(handler(1).on_digit('0', 100, 10, 10, exp, false), digits::done);
+  namespace digits = fmt::detail::digits;
+  EXPECT_EQ(handler(1).on_digit('0', 100, 10, 10, exp, false), digits::error);
   // Check that divisor - error doesn't overflow.
   EXPECT_EQ(handler(1).on_digit('0', 100, 10, 101, exp, false), digits::error);
   // Check that 2 * error doesn't overflow.
@@ -318,7 +309,7 @@
 
 TEST(FPTest, GrisuFormatCompilesWithNonIEEEDouble) {
   fmt::memory_buffer buf;
-  format_float(0.42, -1, fmt::internal::float_specs(), buf);
+  format_float(0.42, -1, fmt::detail::float_specs(), buf);
 }
 
 template <typename T> struct value_extractor {
@@ -328,41 +319,33 @@
     throw std::runtime_error(fmt::format("invalid type {}", typeid(U).name()));
   }
 
-#ifdef __apple_build_version__
+#if FMT_USE_INT128
   // Apple Clang does not define typeid for __int128_t and __uint128_t.
-  FMT_NORETURN T operator()(__int128_t) {
-    throw std::runtime_error(fmt::format("invalid type {}", "__int128_t"));
+  FMT_NORETURN T operator()(fmt::detail::int128_t) {
+    throw std::runtime_error("invalid type __int128_t");
   }
 
-  FMT_NORETURN T operator()(__uint128_t) {
-    throw std::runtime_error(fmt::format("invalid type {}", "__uint128_t"));
+  FMT_NORETURN T operator()(fmt::detail::uint128_t) {
+    throw std::runtime_error("invalid type __uint128_t");
   }
 #endif
 };
 
 TEST(FormatTest, ArgConverter) {
   long long value = max_value<long long>();
-  auto arg = fmt::internal::make_arg<fmt::format_context>(value);
+  auto arg = fmt::detail::make_arg<fmt::format_context>(value);
   fmt::visit_format_arg(
-      fmt::internal::arg_converter<long long, fmt::format_context>(arg, 'd'),
+      fmt::detail::arg_converter<long long, fmt::format_context>(arg, 'd'),
       arg);
   EXPECT_EQ(value, fmt::visit_format_arg(value_extractor<long long>(), arg));
 }
 
-TEST(FormatTest, FormatNegativeNaN) {
-  double nan = std::numeric_limits<double>::quiet_NaN();
-  if (std::signbit(-nan))
-    EXPECT_EQ("-nan", fmt::format("{}", -nan));
-  else
-    fmt::print("Warning: compiler doesn't handle negative NaN correctly");
-}
-
 TEST(FormatTest, StrError) {
   char* message = nullptr;
   char buffer[BUFFER_SIZE];
-  EXPECT_ASSERT(fmt::internal::safe_strerror(EDOM, message = nullptr, 0),
+  EXPECT_ASSERT(fmt::detail::safe_strerror(EDOM, message = nullptr, 0),
                 "invalid buffer");
-  EXPECT_ASSERT(fmt::internal::safe_strerror(EDOM, message = buffer, 0),
+  EXPECT_ASSERT(fmt::detail::safe_strerror(EDOM, message = buffer, 0),
                 "invalid buffer");
   buffer[0] = 'x';
 #if defined(_GNU_SOURCE) && !defined(__COVERITY__)
@@ -374,18 +357,18 @@
 #endif
 
   int result =
-      fmt::internal::safe_strerror(error_code, message = buffer, BUFFER_SIZE);
+      fmt::detail::safe_strerror(error_code, message = buffer, BUFFER_SIZE);
   EXPECT_EQ(result, 0);
-  std::size_t message_size = std::strlen(message);
+  size_t message_size = std::strlen(message);
   EXPECT_GE(BUFFER_SIZE - 1u, message_size);
   EXPECT_EQ(get_system_error(error_code), message);
 
   // safe_strerror never uses buffer on MinGW.
 #if !defined(__MINGW32__) && !defined(__sun)
   result =
-      fmt::internal::safe_strerror(error_code, message = buffer, message_size);
+      fmt::detail::safe_strerror(error_code, message = buffer, message_size);
   EXPECT_EQ(ERANGE, result);
-  result = fmt::internal::safe_strerror(error_code, message = buffer, 1);
+  result = fmt::detail::safe_strerror(error_code, message = buffer, 1);
   EXPECT_EQ(buffer, message);  // Message should point to buffer.
   EXPECT_EQ(ERANGE, result);
   EXPECT_STREQ("", message);
@@ -397,45 +380,48 @@
   {
     fmt::memory_buffer buffer;
     format_to(buffer, "garbage");
-    fmt::internal::format_error_code(buffer, 42, "test");
+    fmt::detail::format_error_code(buffer, 42, "test");
     EXPECT_EQ("test: " + msg, to_string(buffer));
   }
   {
     fmt::memory_buffer buffer;
     std::string prefix(fmt::inline_buffer_size - msg.size() - sep.size() + 1,
                        'x');
-    fmt::internal::format_error_code(buffer, 42, prefix);
+    fmt::detail::format_error_code(buffer, 42, prefix);
     EXPECT_EQ(msg, to_string(buffer));
   }
   int codes[] = {42, -1};
-  for (std::size_t i = 0, n = sizeof(codes) / sizeof(*codes); i < n; ++i) {
+  for (size_t i = 0, n = sizeof(codes) / sizeof(*codes); i < n; ++i) {
     // Test maximum buffer size.
     msg = fmt::format("error {}", codes[i]);
     fmt::memory_buffer buffer;
     std::string prefix(fmt::inline_buffer_size - msg.size() - sep.size(), 'x');
-    fmt::internal::format_error_code(buffer, codes[i], prefix);
+    fmt::detail::format_error_code(buffer, codes[i], prefix);
     EXPECT_EQ(prefix + sep + msg, to_string(buffer));
-    std::size_t size = fmt::inline_buffer_size;
+    size_t size = fmt::inline_buffer_size;
     EXPECT_EQ(size, buffer.size());
     buffer.resize(0);
     // Test with a message that doesn't fit into the buffer.
     prefix += 'x';
-    fmt::internal::format_error_code(buffer, codes[i], prefix);
+    fmt::detail::format_error_code(buffer, codes[i], prefix);
     EXPECT_EQ(msg, to_string(buffer));
   }
 }
 
 TEST(FormatTest, CountCodePoints) {
-  EXPECT_EQ(4, fmt::internal::count_code_points(fmt::u8string_view("ёжик")));
+  EXPECT_EQ(4,
+            fmt::detail::count_code_points(
+                fmt::basic_string_view<fmt::detail::char8_type>(
+                    reinterpret_cast<const fmt::detail::char8_type*>("ёжик"))));
 }
 
-// Tests fmt::internal::count_digits for integer type Int.
+// Tests fmt::detail::count_digits for integer type Int.
 template <typename Int> void test_count_digits() {
-  for (Int i = 0; i < 10; ++i) EXPECT_EQ(1u, fmt::internal::count_digits(i));
+  for (Int i = 0; i < 10; ++i) EXPECT_EQ(1u, fmt::detail::count_digits(i));
   for (Int i = 1, n = 1, end = max_value<Int>() / 10; n <= end; ++i) {
     n *= 10;
-    EXPECT_EQ(i, fmt::internal::count_digits(n - 1));
-    EXPECT_EQ(i + 1, fmt::internal::count_digits(n));
+    EXPECT_EQ(i, fmt::detail::count_digits(n - 1));
+    EXPECT_EQ(i + 1, fmt::detail::count_digits(n));
   }
 }
 
@@ -444,11 +430,17 @@
   test_count_digits<uint64_t>();
 }
 
-TEST(UtilTest, WriteUIntPtr) {
-  fmt::memory_buffer buf;
-  fmt::internal::writer writer(buf);
-  writer.write_pointer(fmt::internal::fallback_uintptr(
-                           reinterpret_cast<void*>(0xface)),
-                       nullptr);
-  EXPECT_EQ("0xface", to_string(buf));
+TEST(UtilTest, WriteFallbackUIntPtr) {
+  std::string s;
+  fmt::detail::write_ptr<char>(
+      std::back_inserter(s),
+      fmt::detail::fallback_uintptr(reinterpret_cast<void*>(0xface)), nullptr);
+  EXPECT_EQ(s, "0xface");
 }
+
+#ifdef _WIN32
+TEST(UtilTest, WriteConsoleSignature) {
+  decltype(WriteConsoleW)* p = fmt::detail::WriteConsoleW;
+  (void)p;
+}
+#endif
diff --git a/test/format-test.cc b/test/format-test.cc
index f52e127..8ed524c 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include <stdint.h>
+
 #include <cctype>
 #include <cfloat>
 #include <climits>
@@ -23,7 +24,6 @@
 // Check if fmt/format.h compiles with the X11 index macro defined.
 #define index(x, y) no nice things
 
-#include "fmt/color.h"
 #include "fmt/format.h"
 
 #undef index
@@ -34,10 +34,6 @@
 #include "util.h"
 
 #undef ERROR
-#undef min
-#undef max
-
-using std::size_t;
 
 using fmt::basic_memory_buffer;
 using fmt::format;
@@ -45,8 +41,8 @@
 using fmt::memory_buffer;
 using fmt::string_view;
 using fmt::wmemory_buffer;
-using fmt::internal::basic_writer;
-using fmt::internal::max_value;
+using fmt::wstring_view;
+using fmt::detail::max_value;
 
 using testing::Return;
 using testing::StrictMock;
@@ -100,47 +96,6 @@
   result = buffer;
 }
 #endif
-
-// Checks if writing value to BasicWriter<Char> produces the same result
-// as writing it to std::basic_ostringstream<Char>.
-template <typename Char, typename T>
-::testing::AssertionResult check_write(const T& value, const char* type) {
-  fmt::basic_memory_buffer<Char> buffer;
-  using range = fmt::buffer_range<Char>;
-  basic_writer<range> writer(buffer);
-  writer.write(value);
-  std::basic_string<Char> actual = to_string(buffer);
-  std::basic_string<Char> expected;
-  std_format(value, expected);
-  if (expected == actual) return ::testing::AssertionSuccess();
-  return ::testing::AssertionFailure()
-         << "Value of: (Writer<" << type << ">() << value).str()\n"
-         << "  Actual: " << actual << "\n"
-         << "Expected: " << expected << "\n";
-}
-
-struct AnyWriteChecker {
-  template <typename T>
-  ::testing::AssertionResult operator()(const char*, const T& value) const {
-    ::testing::AssertionResult result = check_write<char>(value, "char");
-    return result ? check_write<wchar_t>(value, "wchar_t") : result;
-  }
-};
-
-template <typename Char> struct WriteChecker {
-  template <typename T>
-  ::testing::AssertionResult operator()(const char*, const T& value) const {
-    return check_write<Char>(value, "char");
-  }
-};
-
-// Checks if writing value to BasicWriter produces the same result
-// as writing it to std::ostringstream both for char and wchar_t.
-#define CHECK_WRITE(value) EXPECT_PRED_FORMAT1(AnyWriteChecker(), value)
-
-#define CHECK_WRITE_CHAR(value) EXPECT_PRED_FORMAT1(WriteChecker<char>(), value)
-#define CHECK_WRITE_WCHAR(value) \
-  EXPECT_PRED_FORMAT1(WriteChecker<wchar_t>(), value)
 }  // namespace
 
 struct uint32_pair {
@@ -148,10 +103,10 @@
 };
 
 TEST(UtilTest, BitCast) {
-  auto s = fmt::internal::bit_cast<uint32_pair>(uint64_t{42});
-  EXPECT_EQ(fmt::internal::bit_cast<uint64_t>(s), 42ull);
-  s = fmt::internal::bit_cast<uint32_pair>(uint64_t(~0ull));
-  EXPECT_EQ(fmt::internal::bit_cast<uint64_t>(s), ~0ull);
+  auto s = fmt::detail::bit_cast<uint32_pair>(uint64_t{42});
+  EXPECT_EQ(fmt::detail::bit_cast<uint64_t>(s), 42ull);
+  s = fmt::detail::bit_cast<uint32_pair>(uint64_t(~0ull));
+  EXPECT_EQ(fmt::detail::bit_cast<uint64_t>(s), ~0ull);
 }
 
 TEST(UtilTest, Increment) {
@@ -176,26 +131,27 @@
   fmt::string_view s = "10000000000";
   auto begin = s.begin(), end = s.end();
   EXPECT_THROW_MSG(
-      parse_nonnegative_int(begin, end, fmt::internal::error_handler()),
+      parse_nonnegative_int(begin, end, fmt::detail::error_handler()),
       fmt::format_error, "number is too big");
   s = "2147483649";
   begin = s.begin();
   end = s.end();
   EXPECT_THROW_MSG(
-      parse_nonnegative_int(begin, end, fmt::internal::error_handler()),
+      parse_nonnegative_int(begin, end, fmt::detail::error_handler()),
       fmt::format_error, "number is too big");
 }
 
 TEST(IteratorTest, CountingIterator) {
-  fmt::internal::counting_iterator it;
+  fmt::detail::counting_iterator it;
   auto prev = it++;
   EXPECT_EQ(prev.count(), 0);
   EXPECT_EQ(it.count(), 1);
+  EXPECT_EQ((it + 41).count(), 42);
 }
 
 TEST(IteratorTest, TruncatingIterator) {
   char* p = nullptr;
-  fmt::internal::truncating_iterator<char*> it(p, 3);
+  fmt::detail::truncating_iterator<char*> it(p, 3);
   auto prev = it++;
   EXPECT_EQ(prev.base(), p);
   EXPECT_EQ(it.base(), p + 1);
@@ -204,7 +160,7 @@
 TEST(IteratorTest, TruncatingBackInserter) {
   std::string buffer;
   auto bi = std::back_inserter(buffer);
-  fmt::internal::truncating_iterator<decltype(bi)> it(bi, 2);
+  fmt::detail::truncating_iterator<decltype(bi)> it(bi, 2);
   *it++ = '4';
   *it++ = '2';
   *it++ = '1';
@@ -213,20 +169,22 @@
 }
 
 TEST(IteratorTest, IsOutputIterator) {
-  EXPECT_TRUE(fmt::internal::is_output_iterator<char*>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<const char*>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<std::string>::value);
-  EXPECT_TRUE(fmt::internal::is_output_iterator<
-              std::back_insert_iterator<std::string>>::value);
-  EXPECT_TRUE(fmt::internal::is_output_iterator<std::string::iterator>::value);
-  EXPECT_FALSE(
-      fmt::internal::is_output_iterator<std::string::const_iterator>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<std::list<char>>::value);
+  EXPECT_TRUE((fmt::detail::is_output_iterator<char*, char>::value));
+  EXPECT_FALSE((fmt::detail::is_output_iterator<const char*, char>::value));
+  EXPECT_FALSE((fmt::detail::is_output_iterator<std::string, char>::value));
   EXPECT_TRUE(
-      fmt::internal::is_output_iterator<std::list<char>::iterator>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<
-               std::list<char>::const_iterator>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<uint32_pair>::value);
+      (fmt::detail::is_output_iterator<std::back_insert_iterator<std::string>,
+                                       char>::value));
+  EXPECT_TRUE(
+      (fmt::detail::is_output_iterator<std::string::iterator, char>::value));
+  EXPECT_FALSE((fmt::detail::is_output_iterator<std::string::const_iterator,
+                                                char>::value));
+  EXPECT_FALSE((fmt::detail::is_output_iterator<std::list<char>, char>::value));
+  EXPECT_TRUE((
+      fmt::detail::is_output_iterator<std::list<char>::iterator, char>::value));
+  EXPECT_FALSE((fmt::detail::is_output_iterator<std::list<char>::const_iterator,
+                                                char>::value));
+  EXPECT_FALSE((fmt::detail::is_output_iterator<uint32_pair, char>::value));
 }
 
 TEST(MemoryBufferTest, Ctor) {
@@ -280,7 +238,7 @@
   std::allocator<char> alloc;
   basic_memory_buffer<char, 5, TestAllocator> buffer((TestAllocator(&alloc)));
   const char test[] = "test";
-  buffer.append(test, test + 4);
+  buffer.append(string_view(test, 4));
   check_move_buffer("test", buffer);
   // Adding one more character fills the inline buffer, but doesn't cause
   // dynamic allocation.
@@ -337,20 +295,16 @@
 
 TEST(MemoryBufferTest, Grow) {
   typedef allocator_ref<mock_allocator<int>> Allocator;
-  typedef basic_memory_buffer<int, 10, Allocator> Base;
   mock_allocator<int> alloc;
-  struct TestMemoryBuffer : Base {
-    TestMemoryBuffer(Allocator alloc) : Base(alloc) {}
-    void grow(std::size_t size) { Base::grow(size); }
-  } buffer((Allocator(&alloc)));
+  basic_memory_buffer<int, 10, Allocator> buffer((Allocator(&alloc)));
   buffer.resize(7);
-  using fmt::internal::to_unsigned;
+  using fmt::detail::to_unsigned;
   for (int i = 0; i < 7; ++i) buffer[to_unsigned(i)] = i * i;
   EXPECT_EQ(10u, buffer.capacity());
   int mem[20];
   mem[7] = 0xdead;
   EXPECT_CALL(alloc, allocate(20)).WillOnce(Return(mem));
-  buffer.grow(20);
+  buffer.try_reserve(20);
   EXPECT_EQ(20u, buffer.capacity());
   // Check if size elements have been copied
   for (int i = 0; i < 7; ++i) EXPECT_EQ(i * i, buffer[to_unsigned(i)]);
@@ -369,7 +323,7 @@
     basic_memory_buffer<char, 10, TestAllocator> buffer2(
         (TestAllocator(&alloc)));
     EXPECT_EQ(&alloc, buffer2.get_allocator().get());
-    std::size_t size = 2 * fmt::inline_buffer_size;
+    size_t size = 2 * fmt::inline_buffer_size;
     EXPECT_CALL(alloc, allocate(size)).WillOnce(Return(&mem));
     buffer2.reserve(size);
     EXPECT_CALL(alloc, deallocate(&mem, size));
@@ -380,7 +334,7 @@
   typedef allocator_ref<mock_allocator<char>> TestAllocator;
   StrictMock<mock_allocator<char>> alloc;
   basic_memory_buffer<char, 10, TestAllocator> buffer((TestAllocator(&alloc)));
-  std::size_t size = 2 * fmt::inline_buffer_size;
+  size_t size = 2 * fmt::inline_buffer_size;
   std::vector<char> mem(size);
   {
     EXPECT_CALL(alloc, allocate(size)).WillOnce(Return(&mem[0]));
@@ -395,93 +349,31 @@
     EXPECT_THROW(buffer.reserve(2 * size), std::exception);
     EXPECT_EQ(&mem2[0], &buffer[0]);
     // Check that the data has been copied.
-    for (std::size_t i = 0; i < size; ++i) EXPECT_EQ('x', buffer[i]);
+    for (size_t i = 0; i < size; ++i) EXPECT_EQ('x', buffer[i]);
   }
   EXPECT_CALL(alloc, deallocate(&mem2[0], 2 * size));
 }
 
-#ifdef _WIN32
-TEST(UtilTest, UTF16ToUTF8) {
-  std::string s = "ёжик";
-  fmt::internal::utf16_to_utf8 u(L"\x0451\x0436\x0438\x043A");
-  EXPECT_EQ(s, u.str());
-  EXPECT_EQ(s.size(), u.size());
-}
-
-TEST(UtilTest, UTF16ToUTF8EmptyString) {
-  std::string s = "";
-  fmt::internal::utf16_to_utf8 u(L"");
-  EXPECT_EQ(s, u.str());
-  EXPECT_EQ(s.size(), u.size());
-}
-
 TEST(UtilTest, UTF8ToUTF16) {
-  std::string s = "лошадка";
-  fmt::internal::utf8_to_utf16 u(s.c_str());
+  fmt::detail::utf8_to_utf16 u("лошадка");
   EXPECT_EQ(L"\x043B\x043E\x0448\x0430\x0434\x043A\x0430", u.str());
   EXPECT_EQ(7, u.size());
+  // U+10437 { DESERET SMALL LETTER YEE }
+  EXPECT_EQ(L"\xD801\xDC37", fmt::detail::utf8_to_utf16("𐐷").str());
+  EXPECT_THROW_MSG(fmt::detail::utf8_to_utf16("\xc3\x28"), std::runtime_error,
+                   "invalid utf8");
+  EXPECT_THROW_MSG(fmt::detail::utf8_to_utf16(fmt::string_view("л", 1)),
+                   std::runtime_error, "invalid utf8");
+  EXPECT_EQ(L"123456", fmt::detail::utf8_to_utf16("123456").str());
 }
 
 TEST(UtilTest, UTF8ToUTF16EmptyString) {
   std::string s = "";
-  fmt::internal::utf8_to_utf16 u(s.c_str());
+  fmt::detail::utf8_to_utf16 u(s.c_str());
   EXPECT_EQ(L"", u.str());
   EXPECT_EQ(s.size(), u.size());
 }
 
-template <typename Converter, typename Char>
-void check_utf_conversion_error(
-    const char* message,
-    fmt::basic_string_view<Char> str = fmt::basic_string_view<Char>(0, 1)) {
-  fmt::memory_buffer out;
-  fmt::internal::format_windows_error(out, ERROR_INVALID_PARAMETER, message);
-  fmt::system_error error(0, "");
-  try {
-    (Converter)(str);
-  } catch (const fmt::system_error& e) {
-    error = e;
-  }
-  EXPECT_EQ(ERROR_INVALID_PARAMETER, error.error_code());
-  EXPECT_EQ(fmt::to_string(out), error.what());
-}
-
-TEST(UtilTest, UTF16ToUTF8Error) {
-  check_utf_conversion_error<fmt::internal::utf16_to_utf8, wchar_t>(
-      "cannot convert string from UTF-16 to UTF-8");
-}
-
-TEST(UtilTest, UTF8ToUTF16Error) {
-  const char* message = "cannot convert string from UTF-8 to UTF-16";
-  check_utf_conversion_error<fmt::internal::utf8_to_utf16, char>(message);
-  check_utf_conversion_error<fmt::internal::utf8_to_utf16, char>(
-      message, fmt::string_view("foo", INT_MAX + 1u));
-}
-
-TEST(UtilTest, UTF16ToUTF8Convert) {
-  fmt::internal::utf16_to_utf8 u;
-  EXPECT_EQ(ERROR_INVALID_PARAMETER, u.convert(fmt::wstring_view(0, 1)));
-  EXPECT_EQ(ERROR_INVALID_PARAMETER,
-            u.convert(fmt::wstring_view(L"foo", INT_MAX + 1u)));
-}
-#endif  // _WIN32
-
-typedef void (*FormatErrorMessage)(fmt::internal::buffer<char>& out,
-                                   int error_code, string_view message);
-
-template <typename Error>
-void check_throw_error(int error_code, FormatErrorMessage format) {
-  fmt::system_error error(0, "");
-  try {
-    throw Error(error_code, "test {}", "error");
-  } catch (const fmt::system_error& e) {
-    error = e;
-  }
-  fmt::memory_buffer message;
-  format(message, error_code, "test error");
-  EXPECT_EQ(to_string(message), error.what());
-  EXPECT_EQ(error_code, error.error_code());
-}
-
 TEST(UtilTest, FormatSystemError) {
   fmt::memory_buffer message;
   fmt::format_system_error(message, EDOM, "test");
@@ -510,7 +402,17 @@
   fmt::system_error e(EDOM, "test");
   EXPECT_EQ(fmt::format("test: {}", get_system_error(EDOM)), e.what());
   EXPECT_EQ(EDOM, e.error_code());
-  check_throw_error<fmt::system_error>(EDOM, fmt::format_system_error);
+
+  fmt::system_error error(0, "");
+  try {
+    throw fmt::system_error(EDOM, "test {}", "error");
+  } catch (const fmt::system_error& e) {
+    error = e;
+  }
+  fmt::memory_buffer message;
+  fmt::format_system_error(message, EDOM, "test error");
+  EXPECT_EQ(to_string(message), error.what());
+  EXPECT_EQ(EDOM, error.error_code());
 }
 
 TEST(UtilTest, ReportSystemError) {
@@ -521,69 +423,6 @@
                to_string(out));
 }
 
-#ifdef _WIN32
-
-TEST(UtilTest, FormatWindowsError) {
-  LPWSTR message = 0;
-  FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
-                     FORMAT_MESSAGE_IGNORE_INSERTS,
-                 0, ERROR_FILE_EXISTS,
-                 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
-                 reinterpret_cast<LPWSTR>(&message), 0, 0);
-  fmt::internal::utf16_to_utf8 utf8_message(message);
-  LocalFree(message);
-  fmt::memory_buffer actual_message;
-  fmt::internal::format_windows_error(actual_message, ERROR_FILE_EXISTS,
-                                      "test");
-  EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
-            fmt::to_string(actual_message));
-  actual_message.resize(0);
-  fmt::internal::format_windows_error(actual_message, ERROR_FILE_EXISTS,
-                                      fmt::string_view(0, max_value<size_t>()));
-  EXPECT_EQ(fmt::format("error {}", ERROR_FILE_EXISTS),
-            fmt::to_string(actual_message));
-}
-
-TEST(UtilTest, FormatLongWindowsError) {
-  LPWSTR message = 0;
-  // this error code is not available on all Windows platforms and
-  // Windows SDKs, so do not fail the test if the error string cannot
-  // be retrieved.
-  const int provisioning_not_allowed =
-      0x80284013L /*TBS_E_PROVISIONING_NOT_ALLOWED*/;
-  if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
-                         FORMAT_MESSAGE_FROM_SYSTEM |
-                         FORMAT_MESSAGE_IGNORE_INSERTS,
-                     0, static_cast<DWORD>(provisioning_not_allowed),
-                     MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
-                     reinterpret_cast<LPWSTR>(&message), 0, 0) == 0) {
-    return;
-  }
-  fmt::internal::utf16_to_utf8 utf8_message(message);
-  LocalFree(message);
-  fmt::memory_buffer actual_message;
-  fmt::internal::format_windows_error(actual_message, provisioning_not_allowed,
-                                      "test");
-  EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
-            fmt::to_string(actual_message));
-}
-
-TEST(UtilTest, WindowsError) {
-  check_throw_error<fmt::windows_error>(ERROR_FILE_EXISTS,
-                                        fmt::internal::format_windows_error);
-}
-
-TEST(UtilTest, ReportWindowsError) {
-  fmt::memory_buffer out;
-  fmt::internal::format_windows_error(out, ERROR_FILE_EXISTS, "test error");
-  out.push_back('\n');
-  EXPECT_WRITE(stderr,
-               fmt::report_windows_error(ERROR_FILE_EXISTS, "test error"),
-               fmt::to_string(out));
-}
-
-#endif  // _WIN32
-
 TEST(StringViewTest, Ctor) {
   EXPECT_STREQ("abc", string_view("abc").data());
   EXPECT_EQ(3u, string_view("abc").size());
@@ -592,101 +431,6 @@
   EXPECT_EQ(4u, string_view(std::string("defg")).size());
 }
 
-TEST(WriterTest, Data) {
-  memory_buffer buf;
-  fmt::internal::writer w(buf);
-  w.write(42);
-  EXPECT_EQ("42", to_string(buf));
-}
-
-TEST(WriterTest, WriteInt) {
-  CHECK_WRITE(42);
-  CHECK_WRITE(-42);
-  CHECK_WRITE(static_cast<short>(12));
-  CHECK_WRITE(34u);
-  CHECK_WRITE(std::numeric_limits<int>::min());
-  CHECK_WRITE(max_value<int>());
-  CHECK_WRITE(max_value<unsigned>());
-}
-
-TEST(WriterTest, WriteLong) {
-  CHECK_WRITE(56l);
-  CHECK_WRITE(78ul);
-  CHECK_WRITE(std::numeric_limits<long>::min());
-  CHECK_WRITE(max_value<long>());
-  CHECK_WRITE(max_value<unsigned long>());
-}
-
-TEST(WriterTest, WriteLongLong) {
-  CHECK_WRITE(56ll);
-  CHECK_WRITE(78ull);
-  CHECK_WRITE(std::numeric_limits<long long>::min());
-  CHECK_WRITE(max_value<long long>());
-  CHECK_WRITE(max_value<unsigned long long>());
-}
-
-TEST(WriterTest, WriteDouble) {
-  CHECK_WRITE(4.2);
-  CHECK_WRITE(-4.2);
-  auto min = std::numeric_limits<double>::min();
-  auto max = max_value<double>();
-  if (fmt::internal::use_grisu<double>()) {
-    EXPECT_EQ("2.2250738585072014e-308", fmt::format("{}", min));
-    EXPECT_EQ("1.7976931348623157e+308", fmt::format("{}", max));
-  } else {
-    CHECK_WRITE(min);
-    CHECK_WRITE(max);
-  }
-}
-
-TEST(WriterTest, WriteLongDouble) {
-  CHECK_WRITE(4.2l);
-  CHECK_WRITE_CHAR(-4.2l);
-  std::wstring str;
-  std_format(4.2l, str);
-  if (str[0] != '-')
-    CHECK_WRITE_WCHAR(-4.2l);
-  else
-    fmt::print("warning: long double formatting with std::swprintf is broken");
-  auto min = std::numeric_limits<long double>::min();
-  auto max = max_value<long double>();
-  if (fmt::internal::use_grisu<long double>()) {
-    EXPECT_EQ("2.2250738585072014e-308", fmt::format("{}", min));
-    EXPECT_EQ("1.7976931348623157e+308", fmt::format("{}", max));
-  } else {
-    CHECK_WRITE(min);
-    CHECK_WRITE(max);
-  }
-}
-
-TEST(WriterTest, WriteDoubleAtBufferBoundary) {
-  memory_buffer buf;
-  fmt::internal::writer writer(buf);
-  for (int i = 0; i < 100; ++i) writer.write(1.23456789);
-}
-
-TEST(WriterTest, WriteDoubleWithFilledBuffer) {
-  memory_buffer buf;
-  fmt::internal::writer writer(buf);
-  // Fill the buffer.
-  for (int i = 0; i < fmt::inline_buffer_size; ++i) writer.write(' ');
-  writer.write(1.2);
-  fmt::string_view sv(buf.data(), buf.size());
-  sv.remove_prefix(fmt::inline_buffer_size);
-  EXPECT_EQ("1.2", sv);
-}
-
-TEST(WriterTest, WriteChar) { CHECK_WRITE('a'); }
-
-TEST(WriterTest, WriteWideChar) { CHECK_WRITE_WCHAR(L'a'); }
-
-TEST(WriterTest, WriteString) {
-  CHECK_WRITE_CHAR("abc");
-  CHECK_WRITE_WCHAR("abc");
-}
-
-TEST(WriterTest, WriteWideString) { CHECK_WRITE_WCHAR(L"abc"); }
-
 TEST(FormatToTest, FormatWithoutArgs) {
   std::string s;
   fmt::format_to(std::back_inserter(s), "test");
@@ -753,15 +497,14 @@
   EXPECT_THROW_MSG(format("{"), format_error, "invalid format string");
   EXPECT_THROW_MSG(format("{?}"), format_error, "invalid format string");
   EXPECT_THROW_MSG(format("{0"), format_error, "invalid format string");
-  EXPECT_THROW_MSG(format("{0}"), format_error, "argument index out of range");
+  EXPECT_THROW_MSG(format("{0}"), format_error, "argument not found");
   EXPECT_THROW_MSG(format("{00}", 42), format_error, "invalid format string");
 
   char format_str[BUFFER_SIZE];
   safe_sprintf(format_str, "{%u", INT_MAX);
   EXPECT_THROW_MSG(format(format_str), format_error, "invalid format string");
   safe_sprintf(format_str, "{%u}", INT_MAX);
-  EXPECT_THROW_MSG(format(format_str), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(format(format_str), format_error, "argument not found");
 
   safe_sprintf(format_str, "{%u", INT_MAX + 1u);
   EXPECT_THROW_MSG(format(format_str), format_error, "number is too big");
@@ -786,19 +529,18 @@
 TEST(FormatterTest, ManyArgs) {
   EXPECT_EQ("19", TestFormat<20>::format("{19}"));
   EXPECT_THROW_MSG(TestFormat<20>::format("{20}"), format_error,
-                   "argument index out of range");
+                   "argument not found");
   EXPECT_THROW_MSG(TestFormat<21>::format("{21}"), format_error,
-                   "argument index out of range");
-  enum { max_packed_args = fmt::internal::max_packed_args };
+                   "argument not found");
+  enum { max_packed_args = fmt::detail::max_packed_args };
   std::string format_str = fmt::format("{{{}}}", max_packed_args + 1);
   EXPECT_THROW_MSG(TestFormat<max_packed_args>::format(format_str),
-                   format_error, "argument index out of range");
+                   format_error, "argument not found");
 }
 
 TEST(FormatterTest, NamedArg) {
   EXPECT_EQ("1/a/A", format("{_1}/{a_}/{A_}", fmt::arg("a_", 'a'),
                             fmt::arg("A_", "A"), fmt::arg("_1", 1)));
-  EXPECT_THROW_MSG(format("{a}"), format_error, "argument not found");
   EXPECT_EQ(" -42", format("{0:{width}}", -42, fmt::arg("width", 4)));
   EXPECT_EQ("st", format("{0:.{precision}}", "str", fmt::arg("precision", 2)));
   EXPECT_EQ("1 2", format("{} {two}", 1, fmt::arg("two", 2)));
@@ -808,6 +550,8 @@
                          fmt::arg("i", 0), fmt::arg("j", 0), fmt::arg("k", 0),
                          fmt::arg("l", 0), fmt::arg("m", 0), fmt::arg("n", 0),
                          fmt::arg("o", 0), fmt::arg("p", 0)));
+  EXPECT_THROW_MSG(format("{a}"), format_error, "argument not found");
+  EXPECT_THROW_MSG(format("{a}", 42), format_error, "argument not found");
 }
 
 TEST(FormatterTest, AutoArgIndex) {
@@ -821,7 +565,7 @@
                    "cannot switch from manual to automatic argument indexing");
   EXPECT_THROW_MSG(format("{:.{0}}", 1.2345, 2), format_error,
                    "cannot switch from automatic to manual argument indexing");
-  EXPECT_THROW_MSG(format("{}"), format_error, "argument index out of range");
+  EXPECT_THROW_MSG(format("{}"), format_error, "argument not found");
 }
 
 TEST(FormatterTest, EmptySpecs) { EXPECT_EQ("42", format("{0:}", 42)); }
@@ -836,8 +580,8 @@
   EXPECT_EQ("42   ", format("{0:<5}", 42ul));
   EXPECT_EQ("-42  ", format("{0:<5}", -42ll));
   EXPECT_EQ("42   ", format("{0:<5}", 42ull));
-  EXPECT_EQ("-42.0  ", format("{0:<7}", -42.0));
-  EXPECT_EQ("-42.0  ", format("{0:<7}", -42.0l));
+  EXPECT_EQ("-42  ", format("{0:<5}", -42.0));
+  EXPECT_EQ("-42  ", format("{0:<5}", -42.0l));
   EXPECT_EQ("c    ", format("{0:<5}", 'c'));
   EXPECT_EQ("abc  ", format("{0:<5}", "abc"));
   EXPECT_EQ("0xface  ", format("{0:<8}", reinterpret_cast<void*>(0xface)));
@@ -853,45 +597,15 @@
   EXPECT_EQ("   42", format("{0:>5}", 42ul));
   EXPECT_EQ("  -42", format("{0:>5}", -42ll));
   EXPECT_EQ("   42", format("{0:>5}", 42ull));
-  EXPECT_EQ("  -42.0", format("{0:>7}", -42.0));
-  EXPECT_EQ("  -42.0", format("{0:>7}", -42.0l));
+  EXPECT_EQ("  -42", format("{0:>5}", -42.0));
+  EXPECT_EQ("  -42", format("{0:>5}", -42.0l));
   EXPECT_EQ("    c", format("{0:>5}", 'c'));
   EXPECT_EQ("  abc", format("{0:>5}", "abc"));
   EXPECT_EQ("  0xface", format("{0:>8}", reinterpret_cast<void*>(0xface)));
 }
 
-#if FMT_NUMERIC_ALIGN
-TEST(FormatterTest, NumericAlign) {
-  EXPECT_EQ("  42", format("{0:=4}", 42));
-  EXPECT_EQ("+ 42", format("{0:=+4}", 42));
-  EXPECT_EQ("  42", format("{0:=4o}", 042));
-  EXPECT_EQ("+ 42", format("{0:=+4o}", 042));
-  EXPECT_EQ("  42", format("{0:=4x}", 0x42));
-  EXPECT_EQ("+ 42", format("{0:=+4x}", 0x42));
-  EXPECT_EQ("-  42", format("{0:=5}", -42));
-  EXPECT_EQ("   42", format("{0:=5}", 42u));
-  EXPECT_EQ("-  42", format("{0:=5}", -42l));
-  EXPECT_EQ("   42", format("{0:=5}", 42ul));
-  EXPECT_EQ("-  42", format("{0:=5}", -42ll));
-  EXPECT_EQ("   42", format("{0:=5}", 42ull));
-  EXPECT_EQ("-  42.0", format("{0:=7}", -42.0));
-  EXPECT_EQ("-  42.0", format("{0:=7}", -42.0l));
-  EXPECT_THROW_MSG(format("{0:=5", 'c'), format_error,
-                   "missing '}' in format string");
-  EXPECT_THROW_MSG(format("{0:=5}", 'c'), format_error,
-                   "invalid format specifier for char");
-  EXPECT_THROW_MSG(format("{0:=5}", "abc"), format_error,
-                   "format specifier requires numeric argument");
-  EXPECT_THROW_MSG(format("{0:=8}", reinterpret_cast<void*>(0xface)),
-                   format_error, "format specifier requires numeric argument");
-  EXPECT_EQ(" 1.0", fmt::format("{:= }", 1.0));
-}
-
-TEST(FormatToTest, FormatToNonbackInsertIteratorWithSignAndNumericAlignment) {
-  char buffer[16] = {};
-  fmt::format_to(fmt::internal::make_checked(buffer, 16), "{: =+}", 42.0);
-  EXPECT_STREQ("+42.0", buffer);
-}
+#if FMT_DEPRECATED_NUMERIC_ALIGN
+TEST(FormatterTest, NumericAlign) { EXPECT_EQ("0042", format("{0:=4}", 42)); }
 #endif
 
 TEST(FormatterTest, CenterAlign) {
@@ -904,8 +618,8 @@
   EXPECT_EQ(" 42  ", format("{0:^5}", 42ul));
   EXPECT_EQ(" -42 ", format("{0:^5}", -42ll));
   EXPECT_EQ(" 42  ", format("{0:^5}", 42ull));
-  EXPECT_EQ(" -42.0 ", format("{0:^7}", -42.0));
-  EXPECT_EQ(" -42.0 ", format("{0:^7}", -42.0l));
+  EXPECT_EQ(" -42 ", format("{0:^5}", -42.0));
+  EXPECT_EQ(" -42 ", format("{0:^5}", -42.0l));
   EXPECT_EQ("  c  ", format("{0:^5}", 'c'));
   EXPECT_EQ(" abc  ", format("{0:^6}", "abc"));
   EXPECT_EQ(" 0xface ", format("{0:^8}", reinterpret_cast<void*>(0xface)));
@@ -923,13 +637,16 @@
   EXPECT_EQ("***42", format("{0:*>5}", 42ul));
   EXPECT_EQ("**-42", format("{0:*>5}", -42ll));
   EXPECT_EQ("***42", format("{0:*>5}", 42ull));
-  EXPECT_EQ("**-42.0", format("{0:*>7}", -42.0));
-  EXPECT_EQ("**-42.0", format("{0:*>7}", -42.0l));
+  EXPECT_EQ("**-42", format("{0:*>5}", -42.0));
+  EXPECT_EQ("**-42", format("{0:*>5}", -42.0l));
   EXPECT_EQ("c****", format("{0:*<5}", 'c'));
   EXPECT_EQ("abc**", format("{0:*<5}", "abc"));
   EXPECT_EQ("**0xface", format("{0:*>8}", reinterpret_cast<void*>(0xface)));
   EXPECT_EQ("foo=", format("{:}=", "foo"));
   EXPECT_EQ(std::string("\0\0\0*", 4), format(string_view("{:\0>4}", 6), '*'));
+  EXPECT_EQ("жж42", format("{0:ж>4}", 42));
+  EXPECT_THROW_MSG(format("{:\x80\x80\x80\x80\x80>}", 0), format_error,
+                   "missing '}' in format string");
 }
 
 TEST(FormatterTest, PlusSign) {
@@ -944,8 +661,8 @@
   EXPECT_EQ("+42", format("{0:+}", 42ll));
   EXPECT_THROW_MSG(format("{0:+}", 42ull), format_error,
                    "format specifier requires signed argument");
-  EXPECT_EQ("+42.0", format("{0:+}", 42.0));
-  EXPECT_EQ("+42.0", format("{0:+}", 42.0l));
+  EXPECT_EQ("+42", format("{0:+}", 42.0));
+  EXPECT_EQ("+42", format("{0:+}", 42.0l));
   EXPECT_THROW_MSG(format("{0:+", 'c'), format_error,
                    "missing '}' in format string");
   EXPECT_THROW_MSG(format("{0:+}", 'c'), format_error,
@@ -968,8 +685,8 @@
   EXPECT_EQ("42", format("{0:-}", 42ll));
   EXPECT_THROW_MSG(format("{0:-}", 42ull), format_error,
                    "format specifier requires signed argument");
-  EXPECT_EQ("42.0", format("{0:-}", 42.0));
-  EXPECT_EQ("42.0", format("{0:-}", 42.0l));
+  EXPECT_EQ("42", format("{0:-}", 42.0));
+  EXPECT_EQ("42", format("{0:-}", 42.0l));
   EXPECT_THROW_MSG(format("{0:-", 'c'), format_error,
                    "missing '}' in format string");
   EXPECT_THROW_MSG(format("{0:-}", 'c'), format_error,
@@ -992,8 +709,8 @@
   EXPECT_EQ(" 42", format("{0: }", 42ll));
   EXPECT_THROW_MSG(format("{0: }", 42ull), format_error,
                    "format specifier requires signed argument");
-  EXPECT_EQ(" 42.0", format("{0: }", 42.0));
-  EXPECT_EQ(" 42.0", format("{0: }", 42.0l));
+  EXPECT_EQ(" 42", format("{0: }", 42.0));
+  EXPECT_EQ(" 42", format("{0: }", 42.0l));
   EXPECT_THROW_MSG(format("{0: ", 'c'), format_error,
                    "missing '}' in format string");
   EXPECT_THROW_MSG(format("{0: }", 'c'), format_error,
@@ -1004,6 +721,12 @@
                    "format specifier requires numeric argument");
 }
 
+TEST(FormatterTest, SignNotTruncated) {
+  wchar_t format_str[] = {L'{', L':',
+                          '+' | (1 << fmt::detail::num_bits<char>()), L'}', 0};
+  EXPECT_THROW(format(format_str, 42), format_error);
+}
+
 TEST(FormatterTest, HashFlag) {
   EXPECT_EQ("42", format("{0:#}", 42));
   EXPECT_EQ("-42", format("{0:#}", -42));
@@ -1040,6 +763,10 @@
 
   EXPECT_EQ("-42.0", format("{0:#}", -42.0));
   EXPECT_EQ("-42.0", format("{0:#}", -42.0l));
+  EXPECT_EQ("4.e+01", format("{:#.0e}", 42.0));
+  EXPECT_EQ("0.", format("{:#.0f}", 0.01));
+  EXPECT_EQ("0.50", format("{:#.2g}", 0.5));
+  EXPECT_EQ("0.", format("{:#.0f}", 0.5));
   EXPECT_THROW_MSG(format("{0:#", 'c'), format_error,
                    "missing '}' in format string");
   EXPECT_THROW_MSG(format("{0:#}", 'c'), format_error,
@@ -1058,8 +785,8 @@
   EXPECT_EQ("00042", format("{0:05}", 42ul));
   EXPECT_EQ("-0042", format("{0:05}", -42ll));
   EXPECT_EQ("00042", format("{0:05}", 42ull));
-  EXPECT_EQ("-0042.0", format("{0:07}", -42.0));
-  EXPECT_EQ("-0042.0", format("{0:07}", -42.0l));
+  EXPECT_EQ("-000042", format("{0:07}", -42.0));
+  EXPECT_EQ("-000042", format("{0:07}", -42.0l));
   EXPECT_THROW_MSG(format("{0:0", 'c'), format_error,
                    "missing '}' in format string");
   EXPECT_THROW_MSG(format("{0:05}", 'c'), format_error,
@@ -1075,7 +802,7 @@
   safe_sprintf(format_str, "{0:%u", UINT_MAX);
   increment(format_str + 3);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1095,7 +822,9 @@
   EXPECT_EQ("    0xcafe", format("{0:10}", reinterpret_cast<void*>(0xcafe)));
   EXPECT_EQ("x          ", format("{0:11}", 'x'));
   EXPECT_EQ("str         ", format("{0:12}", "str"));
+  EXPECT_EQ(fmt::format("{:*^5}", "🤡"), "**🤡**");
 }
+
 template <typename T> inline T const_check(T value) { return value; }
 
 TEST(FormatterTest, RuntimeWidth) {
@@ -1103,7 +832,7 @@
   safe_sprintf(format_str, "{0:{%u", UINT_MAX);
   increment(format_str + 4);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1115,8 +844,7 @@
   EXPECT_THROW_MSG(format("{0:{}", 0), format_error,
                    "cannot switch from manual to automatic argument indexing");
   EXPECT_THROW_MSG(format("{0:{?}}", 0), format_error, "invalid format string");
-  EXPECT_THROW_MSG(format("{0:{1}}", 0), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(format("{0:{1}}", 0), format_error, "argument not found");
 
   EXPECT_THROW_MSG(format("{0:{0:}}", 0), format_error,
                    "invalid format string");
@@ -1157,7 +885,7 @@
   safe_sprintf(format_str, "{0:.%u", UINT_MAX);
   increment(format_str + 4);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1229,6 +957,11 @@
       "000000000000000000000000000000000000000000000000000P+127",
       format("{:.838A}", -2.14001164E+38));
   EXPECT_EQ("123.", format("{:#.0f}", 123.0));
+  EXPECT_EQ("1.23", format("{:.02f}", 1.234));
+  EXPECT_EQ("0.001", format("{:.1g}", 0.001));
+  EXPECT_EQ("1019666400", format("{}", 1019666432.0f));
+  EXPECT_EQ("1e+01", format("{:.0e}", 9.5));
+  EXPECT_EQ("1.0e-34", fmt::format("{:.1e}", 1e-34));
 
   EXPECT_THROW_MSG(format("{0:.2}", reinterpret_cast<void*>(0xcafe)),
                    format_error,
@@ -1236,6 +969,8 @@
   EXPECT_THROW_MSG(format("{0:.2f}", reinterpret_cast<void*>(0xcafe)),
                    format_error,
                    "precision not allowed for this argument type");
+  EXPECT_THROW_MSG(format("{:.{}e}", 42.0, fmt::detail::max_value<int>()),
+                   format_error, "number is too big");
 
   EXPECT_EQ("st", format("{0:.2}", "str"));
 }
@@ -1245,7 +980,7 @@
   safe_sprintf(format_str, "{0:.{%u", UINT_MAX);
   increment(format_str + 5);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1260,8 +995,7 @@
                    "invalid format string");
   EXPECT_THROW_MSG(format("{0:.{1}", 0, 0), format_error,
                    "precision not allowed for this argument type");
-  EXPECT_THROW_MSG(format("{0:.{1}}", 0), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(format("{0:.{1}}", 0), format_error, "argument not found");
 
   EXPECT_THROW_MSG(format("{0:.{0:}}", 0), format_error,
                    "invalid format string");
@@ -1356,7 +1090,8 @@
 TEST(FormatterTest, FormatInt) {
   EXPECT_THROW_MSG(format("{0:v", 42), format_error,
                    "missing '}' in format string");
-  check_unknown_types(42, "bBdoxXn", "integer");
+  check_unknown_types(42, "bBdoxXnLc", "integer");
+  EXPECT_EQ("x", format("{:c}", static_cast<int>('x')));
 }
 
 TEST(FormatterTest, FormatBin) {
@@ -1496,7 +1231,7 @@
 }
 
 TEST(FormatterTest, FormatIntLocale) {
-  EXPECT_EQ("1234", format("{:n}", 1234));
+  EXPECT_EQ("1234", format("{:L}", 1234));
 }
 
 struct ConvertibleToLongLong {
@@ -1508,19 +1243,23 @@
 }
 
 TEST(FormatterTest, FormatFloat) {
+  EXPECT_EQ("0", format("{}", 0.0f));
   EXPECT_EQ("392.500000", format("{0:f}", 392.5f));
 }
 
 TEST(FormatterTest, FormatDouble) {
-  check_unknown_types(1.2, "eEfFgGaAn%", "double");
-  EXPECT_EQ("0.0", format("{:}", 0.0));
+  EXPECT_EQ("0", format("{}", 0.0));
+  check_unknown_types(1.2, "eEfFgGaAnL%", "double");
+  EXPECT_EQ("0", format("{:}", 0.0));
   EXPECT_EQ("0.000000", format("{:f}", 0.0));
   EXPECT_EQ("0", format("{:g}", 0.0));
   EXPECT_EQ("392.65", format("{:}", 392.65));
   EXPECT_EQ("392.65", format("{:g}", 392.65));
   EXPECT_EQ("392.65", format("{:G}", 392.65));
+  EXPECT_EQ("4.9014e+06", format("{:g}", 4.9014e6));
   EXPECT_EQ("392.650000", format("{:f}", 392.65));
   EXPECT_EQ("392.650000", format("{:F}", 392.65));
+  EXPECT_EQ("42", format("{:L}", 42.0));
   char buffer[BUFFER_SIZE];
   safe_sprintf(buffer, "%e", 392.65);
   EXPECT_EQ(buffer, format("{0:e}", 392.65));
@@ -1531,6 +1270,8 @@
   EXPECT_EQ(buffer, format("{:a}", -42.0));
   safe_sprintf(buffer, "%A", -42.0);
   EXPECT_EQ(buffer, format("{:A}", -42.0));
+  EXPECT_EQ("9223372036854775808.000000",
+            format("{:f}", 9223372036854775807.0));
 }
 
 TEST(FormatterTest, PrecisionRounding) {
@@ -1544,17 +1285,42 @@
   EXPECT_EQ("1.000", format("{:.3f}", 0.9999));
   EXPECT_EQ("0.00123", format("{:.3}", 0.00123));
   EXPECT_EQ("0.1", format("{:.16g}", 0.1));
-  // Trigger rounding error in Grisu by a carefully chosen number.
-  auto n = 3788512123356.985352;
-  char buffer[64];
-  safe_sprintf(buffer, "%f", n);
-  EXPECT_EQ(buffer, format("{:f}", n));
+  EXPECT_EQ("1", fmt::format("{:.0}", 1.0));
+  EXPECT_EQ("225.51575035152063720",
+            fmt::format("{:.17f}", 225.51575035152064));
+  EXPECT_EQ("-761519619559038.2", fmt::format("{:.1f}", -761519619559038.2));
+  EXPECT_EQ("1.9156918820264798e-56",
+            fmt::format("{}", 1.9156918820264798e-56));
+  EXPECT_EQ("0.0000", fmt::format("{:.4f}", 7.2809479766055470e-15));
+
+  // Trigger a rounding error in Grisu by a specially chosen number.
+  EXPECT_EQ("3788512123356.985352", format("{:f}", 3788512123356.985352));
+}
+
+TEST(FormatterTest, PrettifyFloat) {
+  EXPECT_EQ("0.0001", fmt::format("{}", 1e-4));
+  EXPECT_EQ("1e-05", fmt::format("{}", 1e-5));
+  EXPECT_EQ("1000000000000000", fmt::format("{}", 1e15));
+  EXPECT_EQ("1e+16", fmt::format("{}", 1e16));
+  EXPECT_EQ("9.999e-05", fmt::format("{}", 9.999e-5));
+  EXPECT_EQ("10000000000", fmt::format("{}", 1e10));
+  EXPECT_EQ("100000000000", fmt::format("{}", 1e11));
+  EXPECT_EQ("12340000000", fmt::format("{}", 1234e7));
+  EXPECT_EQ("12.34", fmt::format("{}", 1234e-2));
+  EXPECT_EQ("0.001234", fmt::format("{}", 1234e-6));
+  EXPECT_EQ("0.1", fmt::format("{}", 0.1f));
+  EXPECT_EQ("0.10000000149011612", fmt::format("{}", double(0.1f)));
+  EXPECT_EQ("1.3563156e-19", fmt::format("{}", 1.35631564e-19f));
 }
 
 TEST(FormatterTest, FormatNaN) {
   double nan = std::numeric_limits<double>::quiet_NaN();
   EXPECT_EQ("nan", format("{}", nan));
   EXPECT_EQ("+nan", format("{:+}", nan));
+  if (std::signbit(-nan))
+    EXPECT_EQ("-nan", format("{}", -nan));
+  else
+    fmt::print("Warning: compiler doesn't handle negative NaN correctly");
   EXPECT_EQ(" nan", format("{: }", nan));
   EXPECT_EQ("NAN", format("{:F}", nan));
   EXPECT_EQ("nan    ", format("{:<7}", nan));
@@ -1575,7 +1341,7 @@
 }
 
 TEST(FormatterTest, FormatLongDouble) {
-  EXPECT_EQ("0.0", format("{0:}", 0.0l));
+  EXPECT_EQ("0", format("{0:}", 0.0l));
   EXPECT_EQ("0.000000", format("{0:f}", 0.0l));
   EXPECT_EQ("392.65", format("{0:}", 392.65l));
   EXPECT_EQ("392.65", format("{0:g}", 392.65l));
@@ -1591,7 +1357,7 @@
 }
 
 TEST(FormatterTest, FormatChar) {
-  const char types[] = "cbBdoxXn";
+  const char types[] = "cbBdoxXL";
   check_unknown_types('a', types, "char");
   EXPECT_EQ("a", format("{0}", 'a'));
   EXPECT_EQ("z", format("{0:c}", 'z'));
@@ -1685,14 +1451,68 @@
   EXPECT_EQ("test", format("{}", std::string_view("test")));
   EXPECT_EQ("foo", format("{}", string_viewable()));
 }
+
+struct explicitly_convertible_to_std_string_view {
+  explicit operator std::string_view() const { return "foo"; }
+};
+
+namespace fmt {
+template <>
+struct formatter<explicitly_convertible_to_std_string_view>
+    : formatter<std::string_view> {
+  auto format(const explicitly_convertible_to_std_string_view& v,
+              format_context& ctx) -> decltype(ctx.out()) {
+    return format_to(ctx.out(), "'{}'", std::string_view(v));
+  }
+};
+}  // namespace fmt
+
+TEST(FormatterTest, FormatExplicitlyConvertibleToStdStringView) {
+  EXPECT_EQ("'foo'",
+            fmt::format("{}", explicitly_convertible_to_std_string_view()));
+}
 #endif
 
+// std::is_constructible is broken in MSVC until version 2015.
+#if !FMT_MSC_VER || FMT_MSC_VER >= 1900
+struct explicitly_convertible_to_wstring_view {
+  explicit operator fmt::wstring_view() const { return L"foo"; }
+};
+
+TEST(FormatTest, FormatExplicitlyConvertibleToWStringView) {
+  EXPECT_EQ(L"foo",
+            fmt::format(L"{}", explicitly_convertible_to_wstring_view()));
+}
+#endif
+
+namespace fake_qt {
+class QString {
+ public:
+  QString(const wchar_t* s) : s_(std::make_shared<std::wstring>(s)) {}
+  const wchar_t* utf16() const FMT_NOEXCEPT { return s_->data(); }
+  int size() const FMT_NOEXCEPT { return static_cast<int>(s_->size()); }
+
+ private:
+  std::shared_ptr<std::wstring> s_;
+};
+
+fmt::basic_string_view<wchar_t> to_string_view(const QString& s) FMT_NOEXCEPT {
+  return {s.utf16(), static_cast<size_t>(s.size())};
+}
+}  // namespace fake_qt
+
+TEST(FormatTest, FormatForeignStrings) {
+  using fake_qt::QString;
+  EXPECT_EQ(fmt::format(QString(L"{}"), 42), L"42");
+  EXPECT_EQ(fmt::format(QString(L"{}"), QString(L"42")), L"42");
+}
+
 FMT_BEGIN_NAMESPACE
 template <> struct formatter<Date> {
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
     auto it = ctx.begin();
-    if (*it == 'd') ++it;
+    if (it != ctx.end() && *it == 'd') ++it;
     return it;
   }
 
@@ -1728,7 +1548,7 @@
 TEST(FormatterTest, CustomFormatTo) {
   char buf[10] = {};
   auto end =
-      &*fmt::format_to(fmt::internal::make_checked(buf, 10), "{}", Answer());
+      &*fmt::format_to(fmt::detail::make_checked(buf, 10), "{}", Answer());
   EXPECT_EQ(end, buf + 2);
   EXPECT_STREQ(buf, "42");
 }
@@ -1738,6 +1558,7 @@
   EXPECT_EQ(L"4.2", format(L"{}", 4.2));
   EXPECT_EQ(L"abc", format(L"{}", L"abc"));
   EXPECT_EQ(L"z", format(L"{}", L'z'));
+  EXPECT_THROW(fmt::format(L"{:*\x343E}", 42), fmt::format_error);
 }
 
 TEST(FormatterTest, FormatStringFromSpeedTest) {
@@ -1837,6 +1658,8 @@
   EXPECT_WRITE(stderr, fmt::print(stderr, "Don't {}!", "panic"),
                "Don't panic!");
 #endif
+  // Check that the wide print overload compiles.
+  if (fmt::detail::const_check(false)) fmt::print(L"test");
 }
 
 TEST(FormatTest, Variadic) {
@@ -1847,17 +1670,23 @@
 TEST(FormatTest, Dynamic) {
   typedef fmt::format_context ctx;
   std::vector<fmt::basic_format_arg<ctx>> args;
-  args.emplace_back(fmt::internal::make_arg<ctx>(42));
-  args.emplace_back(fmt::internal::make_arg<ctx>("abc1"));
-  args.emplace_back(fmt::internal::make_arg<ctx>(1.5f));
+  args.emplace_back(fmt::detail::make_arg<ctx>(42));
+  args.emplace_back(fmt::detail::make_arg<ctx>("abc1"));
+  args.emplace_back(fmt::detail::make_arg<ctx>(1.5f));
 
   std::string result = fmt::vformat(
-      "{} and {} and {}", fmt::basic_format_args<ctx>(
-                              args.data(), static_cast<unsigned>(args.size())));
+      "{} and {} and {}",
+      fmt::basic_format_args<ctx>(args.data(), static_cast<int>(args.size())));
 
   EXPECT_EQ("42 and abc1 and 1.5", result);
 }
 
+TEST(FormatTest, Bytes) {
+  auto s = fmt::format("{:10}", fmt::bytes("ёжик"));
+  EXPECT_EQ("ёжик  ", s);
+  EXPECT_EQ(10, s.size());
+}
+
 TEST(FormatTest, JoinArg) {
   using fmt::join;
   int v1[3] = {1, 2, 3};
@@ -1929,16 +1758,31 @@
 struct string_like {};
 fmt::string_view to_string_view(string_like) { return "foo"; }
 
+constexpr char with_null[3] = {'{', '}', '\0'};
+constexpr char no_null[2] = {'{', '}'};
+
 TEST(FormatTest, CompileTimeString) {
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), 42));
   EXPECT_EQ(L"42", fmt::format(FMT_STRING(L"{}"), 42));
   EXPECT_EQ("foo", fmt::format(FMT_STRING("{}"), string_like()));
+  (void)with_null;
+  (void)no_null;
+#if __cplusplus >= 201703L
+  EXPECT_EQ("42", fmt::format(FMT_STRING(with_null), 42));
+  EXPECT_EQ("42", fmt::format(FMT_STRING(no_null), 42));
+#endif
+#if defined(FMT_USE_STRING_VIEW) && __cplusplus >= 201703L
+  EXPECT_EQ("42", fmt::format(FMT_STRING(std::string_view("{}")), 42));
+  EXPECT_EQ(L"42", fmt::format(FMT_STRING(std::wstring_view(L"{}")), 42));
+#endif
 }
 
 TEST(FormatTest, CustomFormatCompileTimeString) {
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), Answer()));
   Answer answer;
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), answer));
+  char buf[10] = {};
+  fmt::format_to(buf, FMT_STRING("{}"), answer);
   const Answer const_answer = Answer();
   EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), const_answer));
 }
@@ -2000,58 +1844,6 @@
 }
 #endif
 
-using buffer_range = fmt::buffer_range<char>;
-
-class mock_arg_formatter
-    : public fmt::internal::arg_formatter_base<buffer_range> {
- private:
-#if FMT_USE_INT128
-  MOCK_METHOD1(call, void(__int128_t value));
-#else
-  MOCK_METHOD1(call, void(long long value));
-#endif
-
- public:
-  typedef fmt::internal::arg_formatter_base<buffer_range> base;
-  typedef buffer_range range;
-
-  mock_arg_formatter(fmt::format_context& ctx, fmt::format_parse_context*,
-                     fmt::format_specs* s = nullptr)
-      : base(fmt::internal::get_container(ctx.out()), s, ctx.locale()) {
-    EXPECT_CALL(*this, call(42));
-  }
-
-  template <typename T>
-  typename std::enable_if<fmt::internal::is_integral<T>::value, iterator>::type
-  operator()(T value) {
-    call(value);
-    return base::operator()(value);
-  }
-
-  template <typename T>
-  typename std::enable_if<!fmt::internal::is_integral<T>::value, iterator>::type
-  operator()(T value) {
-    return base::operator()(value);
-  }
-
-  iterator operator()(fmt::basic_format_arg<fmt::format_context>::handle) {
-    return base::operator()(fmt::monostate());
-  }
-};
-
-static void custom_vformat(fmt::string_view format_str, fmt::format_args args) {
-  fmt::memory_buffer buffer;
-  fmt::vformat_to<mock_arg_formatter>(buffer, format_str, args);
-}
-
-template <typename... Args>
-void custom_format(const char* format_str, const Args&... args) {
-  auto va = fmt::make_format_args(args...);
-  return custom_vformat(format_str, va);
-}
-
-TEST(FormatTest, CustomArgFormatter) { custom_format("{}", 42); }
-
 TEST(FormatTest, NonNullTerminatedFormatString) {
   EXPECT_EQ("42", format(string_view("{}foo", 2), 42));
 }
@@ -2081,7 +1873,7 @@
                    "cannot switch from manual to automatic argument indexing");
   EXPECT_THROW_MSG(format("{:{0}}", num), format_error,
                    "cannot switch from automatic to manual argument indexing");
-#if FMT_NUMERIC_ALIGN
+#if FMT_DEPRECATED_NUMERIC_ALIGN
   EXPECT_THROW_MSG(format("{:=}", str), format_error,
                    "format specifier requires numeric argument");
 #endif
@@ -2099,9 +1891,30 @@
                    "precision not allowed for this argument type");
 }
 
+namespace adl_test {
+namespace fmt {
+namespace detail {
+struct foo {};
+template <typename, typename OutputIt> void write(OutputIt, foo) = delete;
+}  // namespace detail
+}  // namespace fmt
+}  // namespace adl_test
+
+FMT_BEGIN_NAMESPACE
+template <>
+struct formatter<adl_test::fmt::detail::foo> : formatter<std::string> {
+  template <typename FormatContext>
+  auto format(adl_test::fmt::detail::foo, FormatContext& ctx)
+      -> decltype(ctx.out()) {
+    return formatter<std::string>::format("foo", ctx);
+  }
+};
+FMT_END_NAMESPACE
+
 TEST(FormatTest, ToString) {
   EXPECT_EQ("42", fmt::to_string(42));
   EXPECT_EQ("0x1234", fmt::to_string(reinterpret_cast<void*>(0x1234)));
+  EXPECT_EQ("foo", fmt::to_string(adl_test::fmt::detail::foo()));
 }
 
 TEST(FormatTest, ToWString) { EXPECT_EQ(L"42", fmt::to_wstring(42)); }
@@ -2119,6 +1932,12 @@
   EXPECT_EQ(2u, fmt::formatted_size("{}", 42));
 }
 
+TEST(FormatTest, FormatTo) {
+  std::vector<char> v;
+  fmt::format_to(std::back_inserter(v), "{}", "foo");
+  EXPECT_EQ(string_view(v.data(), v.size()), "foo");
+}
+
 TEST(FormatTest, FormatToN) {
   char buffer[4];
   buffer[3] = 'x';
@@ -2126,10 +1945,12 @@
   EXPECT_EQ(5u, result.size);
   EXPECT_EQ(buffer + 3, result.out);
   EXPECT_EQ("123x", fmt::string_view(buffer, 4));
+
   result = fmt::format_to_n(buffer, 3, "{:s}", "foobar");
   EXPECT_EQ(6u, result.size);
   EXPECT_EQ(buffer + 3, result.out);
   EXPECT_EQ("foox", fmt::string_view(buffer, 4));
+
   buffer[0] = 'x';
   buffer[1] = 'x';
   buffer[2] = 'x';
@@ -2137,10 +1958,20 @@
   EXPECT_EQ(1u, result.size);
   EXPECT_EQ(buffer + 1, result.out);
   EXPECT_EQ("Axxx", fmt::string_view(buffer, 4));
+
   result = fmt::format_to_n(buffer, 3, "{}{} ", 'B', 'C');
   EXPECT_EQ(3u, result.size);
   EXPECT_EQ(buffer + 3, result.out);
   EXPECT_EQ("BC x", fmt::string_view(buffer, 4));
+
+  result = fmt::format_to_n(buffer, 4, "{}", "ABCDE");
+  EXPECT_EQ(5u, result.size);
+  EXPECT_EQ("ABCD", fmt::string_view(buffer, 4));
+
+  buffer[3] = 'x';
+  result = fmt::format_to_n(buffer, 3, "{}", std::string(1000, '*'));
+  EXPECT_EQ(1000u, result.size);
+  EXPECT_EQ("***x", fmt::string_view(buffer, 4));
 }
 
 TEST(FormatTest, WideFormatToN) {
@@ -2163,16 +1994,43 @@
   EXPECT_EQ(L"BC x", fmt::wstring_view(buffer, 4));
 }
 
+struct test_output_iterator {
+  char* data;
+
+  using iterator_category = std::output_iterator_tag;
+  using value_type = void;
+  using difference_type = void;
+  using pointer = void;
+  using reference = void;
+
+  test_output_iterator& operator++() {
+    ++data;
+    return *this;
+  }
+  test_output_iterator operator++(int) {
+    auto tmp = *this;
+    ++data;
+    return tmp;
+  }
+  char& operator*() { return *data; }
+};
+
+TEST(FormatTest, FormatToNOutputIterator) {
+  char buf[10] = {};
+  fmt::format_to_n(test_output_iterator{buf}, 10, "{}", 42);
+  EXPECT_STREQ(buf, "42");
+}
+
 #if FMT_USE_CONSTEXPR
 struct test_arg_id_handler {
   enum result { NONE, EMPTY, INDEX, NAME, ERROR };
   result res = NONE;
-  unsigned index = 0;
+  int index = 0;
   string_view name;
 
   FMT_CONSTEXPR void operator()() { res = EMPTY; }
 
-  FMT_CONSTEXPR void operator()(unsigned i) {
+  FMT_CONSTEXPR void operator()(int i) {
     res = INDEX;
     index = i;
   }
@@ -2188,7 +2046,7 @@
 template <size_t N>
 FMT_CONSTEXPR test_arg_id_handler parse_arg_id(const char (&s)[N]) {
   test_arg_id_handler h;
-  fmt::internal::parse_arg_id(s, s + N, h);
+  fmt::detail::parse_arg_id(s, s + N, h);
   return h;
 }
 
@@ -2208,10 +2066,10 @@
 
   fmt::align_t align = fmt::align::none;
   char fill = 0;
-  unsigned width = 0;
-  fmt::internal::arg_ref<char> width_ref;
-  unsigned precision = 0;
-  fmt::internal::arg_ref<char> precision_ref;
+  int width = 0;
+  fmt::detail::arg_ref<char> width_ref;
+  int precision = 0;
+  fmt::detail::arg_ref<char> precision_ref;
   char type = 0;
 
   // Workaround for MSVC2017 bug that results in "expression did not evaluate
@@ -2229,23 +2087,21 @@
         type(other.type) {}
 
   FMT_CONSTEXPR void on_align(fmt::align_t a) { align = a; }
-  FMT_CONSTEXPR void on_fill(char f) { fill = f; }
+  FMT_CONSTEXPR void on_fill(fmt::string_view f) { fill = f[0]; }
   FMT_CONSTEXPR void on_plus() { res = PLUS; }
   FMT_CONSTEXPR void on_minus() { res = MINUS; }
   FMT_CONSTEXPR void on_space() { res = SPACE; }
   FMT_CONSTEXPR void on_hash() { res = HASH; }
   FMT_CONSTEXPR void on_zero() { res = ZERO; }
 
-  FMT_CONSTEXPR void on_width(unsigned w) { width = w; }
-  FMT_CONSTEXPR void on_dynamic_width(fmt::internal::auto_id) {}
-  FMT_CONSTEXPR void on_dynamic_width(unsigned index) { width_ref = index; }
+  FMT_CONSTEXPR void on_width(int w) { width = w; }
+  FMT_CONSTEXPR void on_dynamic_width(fmt::detail::auto_id) {}
+  FMT_CONSTEXPR void on_dynamic_width(int index) { width_ref = index; }
   FMT_CONSTEXPR void on_dynamic_width(string_view) {}
 
-  FMT_CONSTEXPR void on_precision(unsigned p) { precision = p; }
-  FMT_CONSTEXPR void on_dynamic_precision(fmt::internal::auto_id) {}
-  FMT_CONSTEXPR void on_dynamic_precision(unsigned index) {
-    precision_ref = index;
-  }
+  FMT_CONSTEXPR void on_precision(int p) { precision = p; }
+  FMT_CONSTEXPR void on_dynamic_precision(fmt::detail::auto_id) {}
+  FMT_CONSTEXPR void on_dynamic_precision(int index) { precision_ref = index; }
   FMT_CONSTEXPR void on_dynamic_precision(string_view) {}
 
   FMT_CONSTEXPR void end_precision() {}
@@ -2256,7 +2112,7 @@
 template <size_t N>
 FMT_CONSTEXPR test_format_specs_handler parse_test_specs(const char (&s)[N]) {
   test_format_specs_handler h;
-  fmt::internal::parse_format_specs(s, s + N, h);
+  fmt::detail::parse_format_specs(s, s + N, h);
   return h;
 }
 
@@ -2280,7 +2136,7 @@
 struct test_parse_context {
   typedef char char_type;
 
-  FMT_CONSTEXPR unsigned next_arg_id() { return 11; }
+  FMT_CONSTEXPR int next_arg_id() { return 11; }
   template <typename Id> FMT_CONSTEXPR void check_arg_id(Id) {}
 
   FMT_CONSTEXPR const char* begin() { return nullptr; }
@@ -2290,8 +2146,9 @@
 };
 
 struct test_context {
-  typedef char char_type;
-  typedef fmt::basic_format_arg<test_context> format_arg;
+  using char_type = char;
+  using format_arg = fmt::basic_format_arg<test_context>;
+  using parse_context_type = fmt::format_parse_context;
 
   template <typename T> struct formatter_type {
     typedef fmt::formatter<T, char_type> type;
@@ -2299,7 +2156,7 @@
 
   template <typename Id>
   FMT_CONSTEXPR fmt::basic_format_arg<test_context> arg(Id id) {
-    return fmt::internal::make_arg<test_context>(id);
+    return fmt::detail::make_arg<test_context>(id);
   }
 
   void on_error(const char*) {}
@@ -2312,7 +2169,7 @@
   auto specs = fmt::format_specs();
   auto parse_ctx = test_parse_context();
   auto ctx = test_context();
-  fmt::internal::specs_handler<test_parse_context, test_context> h(
+  fmt::detail::specs_handler<test_parse_context, test_context> h(
       specs, parse_ctx, ctx);
   parse_format_specs(s, s + N, h);
   return specs;
@@ -2336,11 +2193,11 @@
 }
 
 template <size_t N>
-FMT_CONSTEXPR fmt::internal::dynamic_format_specs<char> parse_dynamic_specs(
+FMT_CONSTEXPR fmt::detail::dynamic_format_specs<char> parse_dynamic_specs(
     const char (&s)[N]) {
-  fmt::internal::dynamic_format_specs<char> specs;
+  fmt::detail::dynamic_format_specs<char> specs;
   test_parse_context ctx{};
-  fmt::internal::dynamic_specs_handler<test_parse_context> h(specs, ctx);
+  fmt::detail::dynamic_specs_handler<test_parse_context> h(specs, ctx);
   parse_format_specs(s, s + N, h);
   return specs;
 }
@@ -2364,8 +2221,8 @@
 
 template <size_t N>
 FMT_CONSTEXPR test_format_specs_handler check_specs(const char (&s)[N]) {
-  fmt::internal::specs_checker<test_format_specs_handler> checker(
-      test_format_specs_handler(), fmt::internal::double_type);
+  fmt::detail::specs_checker<test_format_specs_handler> checker(
+      test_format_specs_handler(), fmt::detail::type::double_type);
   parse_format_specs(s, s + N, checker);
   return checker;
 }
@@ -2390,13 +2247,14 @@
 struct test_format_string_handler {
   FMT_CONSTEXPR void on_text(const char*, const char*) {}
 
-  FMT_CONSTEXPR void on_arg_id() {}
+  FMT_CONSTEXPR int on_arg_id() { return 0; }
 
-  template <typename T> FMT_CONSTEXPR void on_arg_id(T) {}
+  template <typename T> FMT_CONSTEXPR int on_arg_id(T) { return 0; }
 
-  FMT_CONSTEXPR void on_replacement_field(const char*) {}
+  FMT_CONSTEXPR void on_replacement_field(int, const char*) {}
 
-  FMT_CONSTEXPR const char* on_format_specs(const char* begin, const char*) {
+  FMT_CONSTEXPR const char* on_format_specs(int, const char* begin,
+                                            const char*) {
     return begin;
   }
 
@@ -2407,7 +2265,7 @@
 
 template <size_t N> FMT_CONSTEXPR bool parse_string(const char (&s)[N]) {
   test_format_string_handler h;
-  fmt::internal::parse_format_string<true>(fmt::string_view(s, N - 1), h);
+  fmt::detail::parse_format_string<true>(fmt::string_view(s, N - 1), h);
   return !h.error;
 }
 
@@ -2451,8 +2309,10 @@
 template <typename... Args>
 FMT_CONSTEXPR bool test_error(const char* fmt, const char* expected_error) {
   const char* actual_error = nullptr;
-  fmt::internal::do_check_format_string<char, test_error_handler, Args...>(
-      string_view(fmt, len(fmt)), test_error_handler(actual_error));
+  string_view s(fmt, len(fmt));
+  fmt::detail::format_string_checker<char, test_error_handler, Args...> checker(
+      s, test_error_handler(actual_error));
+  fmt::detail::parse_format_string<true>(s, checker);
   return equal(actual_error, expected_error);
 }
 
@@ -2465,13 +2325,13 @@
   EXPECT_ERROR_NOARGS("foo", nullptr);
   EXPECT_ERROR_NOARGS("}", "unmatched '}' in format string");
   EXPECT_ERROR("{0:s", "unknown format specifier", Date);
-#  if FMT_MSC_VER >= 1916
-  // This causes an internal compiler error in MSVC2017.
+#  if !FMT_MSC_VER || FMT_MSC_VER >= 1916
+  // This causes an detail compiler error in MSVC2017.
   EXPECT_ERROR("{:{<}", "invalid fill character '{'", int);
   EXPECT_ERROR("{:10000000000}", "number is too big", int);
   EXPECT_ERROR("{:.10000000000}", "number is too big", int);
-  EXPECT_ERROR_NOARGS("{:x}", "argument index out of range");
-#    if FMT_NUMERIC_ALIGN
+  EXPECT_ERROR_NOARGS("{:x}", "argument not found");
+#    if FMT_DEPRECATED_NUMERIC_ALIGN
   EXPECT_ERROR("{0:=5", "unknown format specifier", int);
   EXPECT_ERROR("{:=}", "format specifier requires numeric argument",
                const char*);
@@ -2489,6 +2349,8 @@
   EXPECT_ERROR("{:+}", "format specifier requires signed argument", unsigned);
   EXPECT_ERROR("{:-}", "format specifier requires signed argument", unsigned);
   EXPECT_ERROR("{: }", "format specifier requires signed argument", unsigned);
+  EXPECT_ERROR("{:{}}", "argument not found", int);
+  EXPECT_ERROR("{:.{}}", "argument not found", double);
   EXPECT_ERROR("{:.2}", "precision not allowed for this argument type", int);
   EXPECT_ERROR("{:s}", "invalid type specifier", int);
   EXPECT_ERROR("{:s}", "invalid type specifier", bool);
@@ -2511,8 +2373,8 @@
   EXPECT_ERROR("{:.{0x}}", "invalid format string", int);
   EXPECT_ERROR("{:.{-}}", "invalid format string", int);
   EXPECT_ERROR("{:.x}", "missing precision specifier", int);
-  EXPECT_ERROR_NOARGS("{}", "argument index out of range");
-  EXPECT_ERROR("{1}", "argument index out of range", int);
+  EXPECT_ERROR_NOARGS("{}", "argument not found");
+  EXPECT_ERROR("{1}", "argument not found", int);
   EXPECT_ERROR("{1}{}",
                "cannot switch from manual to automatic argument indexing", int,
                int);
@@ -2523,7 +2385,7 @@
 
 TEST(FormatTest, VFormatTo) {
   typedef fmt::format_context context;
-  fmt::basic_format_arg<context> arg = fmt::internal::make_arg<context>(42);
+  fmt::basic_format_arg<context> arg = fmt::detail::make_arg<context>(42);
   fmt::basic_format_args<context> args(&arg, 1);
   std::string s;
   fmt::vformat_to(std::back_inserter(s), "{}", args);
@@ -2533,7 +2395,7 @@
   EXPECT_EQ("42", s);
 
   typedef fmt::wformat_context wcontext;
-  fmt::basic_format_arg<wcontext> warg = fmt::internal::make_arg<wcontext>(42);
+  fmt::basic_format_arg<wcontext> warg = fmt::detail::make_arg<wcontext>(42);
   fmt::basic_format_args<wcontext> wargs(&warg, 1);
   std::wstring w;
   fmt::vformat_to(std::back_inserter(w), L"{}", wargs);
@@ -2554,54 +2416,8 @@
 
 #endif  // FMT_USE_CONSTEXPR
 
-// C++20 feature test, since r346892 Clang considers char8_t a fundamental
-// type in this mode. If this is the case __cpp_char8_t will be defined.
-#ifndef __cpp_char8_t
-// Locally provide type char8_t defined in format.h
-using fmt::char8_t;
-#endif
-
-TEST(FormatTest, ConstructU8StringViewFromCString) {
-  fmt::u8string_view s("ab");
-  EXPECT_EQ(s.size(), 2u);
-  const char8_t* data = s.data();
-  EXPECT_EQ(data[0], 'a');
-  EXPECT_EQ(data[1], 'b');
-}
-
-TEST(FormatTest, ConstructU8StringViewFromDataAndSize) {
-  fmt::u8string_view s("foobar", 3);
-  EXPECT_EQ(s.size(), 3u);
-  const char8_t* data = s.data();
-  EXPECT_EQ(data[0], 'f');
-  EXPECT_EQ(data[1], 'o');
-  EXPECT_EQ(data[2], 'o');
-}
-
-#if FMT_USE_USER_DEFINED_LITERALS
-TEST(FormatTest, U8StringViewLiteral) {
-  using namespace fmt::literals;
-  fmt::u8string_view s = "ab"_u;
-  EXPECT_EQ(s.size(), 2u);
-  const char8_t* data = s.data();
-  EXPECT_EQ(data[0], 'a');
-  EXPECT_EQ(data[1], 'b');
-  EXPECT_EQ(format("{:*^5}"_u, "🤡"_u), "**🤡**"_u);
-}
-#endif
-
-TEST(FormatTest, FormatU8String) {
-  EXPECT_EQ(format(fmt::u8string_view("{}"), 42), fmt::u8string_view("42"));
-}
-
-TEST(FormatTest, EmphasisNonHeaderOnly) {
-  // ensure this compiles even if FMT_HEADER_ONLY is not defined.
-  EXPECT_EQ(fmt::format(fmt::emphasis::bold, "bold error"),
-            "\x1b[1mbold error\x1b[0m");
-}
-
 TEST(FormatTest, CharTraitsIsNotAmbiguous) {
-  // Test that we don't inject internal names into the std namespace.
+  // Test that we don't inject detail names into the std namespace.
   using namespace std;
   char_traits<char>::char_type c;
   (void)c;
@@ -2612,32 +2428,68 @@
 #endif
 }
 
-struct mychar {
+#if __cplusplus > 201103L
+struct custom_char {
   int value;
-  mychar() = default;
+  custom_char() = default;
 
-  template <typename T> mychar(T val) : value(static_cast<int>(val)) {}
+  template <typename T>
+  constexpr custom_char(T val) : value(static_cast<int>(val)) {}
 
   operator int() const { return value; }
 };
 
+int to_ascii(custom_char c) { return c; }
+
 FMT_BEGIN_NAMESPACE
-template <> struct is_char<mychar> : std::true_type {};
+template <> struct is_char<custom_char> : std::true_type {};
 FMT_END_NAMESPACE
 
 TEST(FormatTest, FormatCustomChar) {
-  const mychar format[] = {'{', '}', 0};
-  auto result = fmt::format(format, mychar('x'));
+  const custom_char format[] = {'{', '}', 0};
+  auto result = fmt::format(format, custom_char('x'));
   EXPECT_EQ(result.size(), 1);
-  EXPECT_EQ(result[0], mychar('x'));
+  EXPECT_EQ(result[0], custom_char('x'));
+}
+#endif
+
+// Convert a char8_t string to std::string. Otherwise GTest will insist on
+// inserting `char8_t` NTBS into a `char` stream which is disabled by P1423.
+template <typename S> std::string from_u8str(const S& str) {
+  return std::string(str.begin(), str.end());
 }
 
 TEST(FormatTest, FormatUTF8Precision) {
-  using str_type = std::basic_string<char8_t>;
-  str_type format(reinterpret_cast<const char8_t*>(u8"{:.4}"));
-  str_type str(reinterpret_cast<const char8_t*>(u8"caf\u00e9s"));  // cafés
+  using str_type = std::basic_string<fmt::detail::char8_type>;
+  str_type format(reinterpret_cast<const fmt::detail::char8_type*>(u8"{:.4}"));
+  str_type str(reinterpret_cast<const fmt::detail::char8_type*>(
+      u8"caf\u00e9s"));  // cafés
   auto result = fmt::format(format, str);
-  EXPECT_EQ(fmt::internal::count_code_points(result), 4);
+  EXPECT_EQ(fmt::detail::count_code_points(result), 4);
   EXPECT_EQ(result.size(), 5);
-  EXPECT_EQ(result, str.substr(0, 5));
+  EXPECT_EQ(from_u8str(result), from_u8str(str.substr(0, 5)));
+}
+
+struct check_back_appender {};
+
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<check_back_appender> {
+  template <typename ParseContext>
+  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename Context>
+  auto format(check_back_appender, Context& ctx) -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    static_assert(std::is_same<decltype(++out), decltype(out)&>::value,
+                  "needs to satisfy weakly_incrementable");
+    *out = 'y';
+    return ++out;
+  }
+};
+FMT_END_NAMESPACE
+
+TEST(FormatTest, BackInsertSlicing) {
+  EXPECT_EQ(fmt::format("{}", check_back_appender{}), "y");
 }
diff --git a/test/fuzzing/CMakeLists.txt b/test/fuzzing/CMakeLists.txt
index 31344fc..2f716d8 100644
--- a/test/fuzzing/CMakeLists.txt
+++ b/test/fuzzing/CMakeLists.txt
@@ -1,38 +1,30 @@
 # Copyright (c) 2019, Paul Dreik
 # License: see LICENSE.rst in the fmt root directory
 
-# settings this links in a main. useful for reproducing,
-# kcov, gdb, afl, valgrind.
-# (note that libFuzzer can also reproduce, just pass it the files)
-option(FMT_FUZZ_LINKMAIN "enables the reproduce mode, instead of libFuzzer" On)
+# Link in the main function. Useful for reproducing, kcov, gdb, afl, valgrind.
+# (Note that libFuzzer can also reproduce, just pass it the files.)
+option(FMT_FUZZ_LINKMAIN "Enables the reproduce mode, instead of libFuzzer" On)
 
 # For oss-fuzz - insert $LIB_FUZZING_ENGINE into the link flags, but only for
-# the fuzz targets, otherwise the cmake configuration step fails.
+# the fuzz targets, otherwise the CMake configuration step fails.
 set(FMT_FUZZ_LDFLAGS "" CACHE STRING "LDFLAGS for the fuzz targets")
 
-# Find all fuzzers.
-set(SOURCES
-  chrono_duration.cpp
-  named_arg.cpp
-  one_arg.cpp
-  sprintf.cpp
-  two_args.cpp
-)
-
-macro(implement_fuzzer sourcefile)
-  get_filename_component(basename ${sourcefile} NAME_WE)
-  set(name fuzzer_${basename})
-  add_executable(${name} ${sourcefile} fuzzer_common.h)
+# Adds a binary for reproducing, i.e. no fuzzing, just enables replaying data
+# through the fuzzers.
+function(add_fuzzer source)
+  get_filename_component(basename ${source} NAME_WE)
+  set(name ${basename}-fuzzer)
+  add_executable(${name} ${source} fuzzer-common.h)
   if (FMT_FUZZ_LINKMAIN)
-      target_sources(${name} PRIVATE main.cpp)
+    target_sources(${name} PRIVATE main.cc)
   endif ()
   target_link_libraries(${name} PRIVATE fmt)
-if (FMT_FUZZ_LDFLAGS)
-  target_link_libraries(${name} PRIVATE ${FMT_FUZZ_LDFLAGS})
-endif ()
+  if (FMT_FUZZ_LDFLAGS)
+    target_link_libraries(${name} PRIVATE ${FMT_FUZZ_LDFLAGS})
+  endif ()
   target_compile_features(${name} PRIVATE cxx_generic_lambdas)
-endmacro ()
+endfunction()
 
-foreach (X IN ITEMS ${SOURCES})
-  implement_fuzzer(${X})
+foreach (source chrono-duration.cc float.cc named-arg.cc one-arg.cc two-args.cc)
+  add_fuzzer(${source})
 endforeach ()
diff --git a/test/fuzzing/README.md b/test/fuzzing/README.md
index 0499d00..bb3d0e0 100644
--- a/test/fuzzing/README.md
+++ b/test/fuzzing/README.md
@@ -1,22 +1,4 @@
-# FMT Fuzzer
-
-Fuzzing has revealed [several bugs](https://github.com/fmtlib/fmt/issues?&q=is%3Aissue+fuzz)
-in fmt. It is a part of the continous fuzzing at
-[oss-fuzz](https://github.com/google/oss-fuzz).
-
-The source code is modified to make the fuzzing possible without locking up on
-resource exhaustion:
-```cpp
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-if(spec.precision>100000) {
-  throw std::runtime_error("fuzz mode - avoiding large precision");
-}
-#endif
-```
-This macro is the defacto standard for making fuzzing practically possible, see
-[the libFuzzer documentation](https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode).
-
-## Running the fuzzers locally
+# Running the fuzzers locally
 
 There is a [helper script](build.sh) to build the fuzzers, which has only been
 tested on Debian and Ubuntu linux so far. There should be no problems fuzzing on
@@ -29,7 +11,7 @@
 cd build
 export CXX=clang++
 export CXXFLAGS="-fsanitize=fuzzer-no-link -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION= -g"
-cmake ..  -DFMT_SAFE_DURATION_CAST=On -DFMT_FUZZ=On -DFMT_FUZZ_LINKMAIN=Off -DFMT_FUZZ_LDFLAGS="-fsanitize=fuzzer"
+cmake .. -DFMT_SAFE_DURATION_CAST=On -DFMT_FUZZ=On -DFMT_FUZZ_LINKMAIN=Off -DFMT_FUZZ_LDFLAGS="-fsanitize=fuzzer"
 cmake --build .
 ```
 should work to build the fuzzers for all platforms which clang supports.
@@ -39,5 +21,5 @@
 cd build
 export UBSAN_OPTIONS=halt_on_error=1
 mkdir out_chrono
-bin/fuzzer_chrono_duration  out_chrono
+bin/fuzzer_chrono_duration out_chrono
 ```
diff --git a/test/fuzzing/build.sh b/test/fuzzing/build.sh
index 141a50d..28c5063 100755
--- a/test/fuzzing/build.sh
+++ b/test/fuzzing/build.sh
@@ -1,7 +1,6 @@
 #!/bin/sh
 #
 # Creates fuzzer builds of various kinds
-# - reproduce mode (no fuzzing, just enables replaying data through the fuzzers)
 # - oss-fuzz emulated mode (makes sure a simulated invocation by oss-fuzz works)
 # - libFuzzer build (you will need clang)
 # - afl build (you will need afl)
@@ -9,7 +8,7 @@
 #
 # Copyright (c) 2019 Paul Dreik
 #
-# License: see LICENSE.rst in the fmt root directory
+# For the license information refer to format.h.
 
 set -e
 me=$(basename $0)
@@ -23,16 +22,7 @@
 CXXFLAGSALL="-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION= -g"
 CMAKEFLAGSALL="$root -GNinja -DCMAKE_BUILD_TYPE=Debug -DFMT_DOC=Off -DFMT_TEST=Off -DFMT_FUZZ=On -DCMAKE_CXX_STANDARD=17"
 
-#builds the fuzzers as one would do if using afl or just making
-#binaries for reproducing.
-builddir=$here/build-fuzzers-reproduce
-mkdir -p $builddir
-cd $builddir
-CXX="ccache g++" CXXFLAGS="$CXXFLAGSALL" cmake \
-$CMAKEFLAGSALL
-cmake --build $builddir
-
-#for performance analysis of the fuzzers
+# For performance analysis of the fuzzers.
 builddir=$here/build-fuzzers-perfanalysis
 mkdir -p $builddir
 cd $builddir
@@ -43,7 +33,7 @@
 
 cmake --build $builddir
 
-#builds the fuzzers as oss-fuzz does
+# Builds the fuzzers as oss-fuzz does.
 builddir=$here/build-fuzzers-ossfuzz
 mkdir -p $builddir
 cd $builddir
@@ -56,7 +46,7 @@
 cmake --build $builddir
 
 
-#builds fuzzers for local fuzzing with libfuzzer with asan+usan
+# Builds fuzzers for local fuzzing with libfuzzer with asan+usan.
 builddir=$here/build-fuzzers-libfuzzer
 mkdir -p $builddir
 cd $builddir
@@ -68,19 +58,7 @@
 
 cmake --build $builddir
 
-#builds fuzzers for local fuzzing with libfuzzer with asan only
-builddir=$here/build-fuzzers-libfuzzer-addr
-mkdir -p $builddir
-cd $builddir
-CXX="clang++" \
-CXXFLAGS="$CXXFLAGSALL -fsanitize=fuzzer-no-link,undefined" cmake \
-cmake $CMAKEFLAGSALL \
--DFMT_FUZZ_LINKMAIN=Off \
--DFMT_FUZZ_LDFLAGS="-fsanitize=fuzzer"
-
-cmake --build $builddir
-
-#builds a fast fuzzer for making coverage fast
+# Builds a fast fuzzer for making coverage fast.
 builddir=$here/build-fuzzers-fast
 mkdir -p $builddir
 cd $builddir
@@ -94,7 +72,7 @@
 cmake --build $builddir
 
 
-#builds fuzzers for local fuzzing with afl
+# Builds fuzzers for local fuzzing with afl.
 builddir=$here/build-fuzzers-afl
 mkdir -p $builddir
 cd $builddir
diff --git a/test/fuzzing/chrono-duration.cc b/test/fuzzing/chrono-duration.cc
new file mode 100644
index 0000000..fdad989
--- /dev/null
+++ b/test/fuzzing/chrono-duration.cc
@@ -0,0 +1,135 @@
+// Copyright (c) 2019, Paul Dreik
+// For the license information refer to format.h.
+
+#include <cstdint>
+#include <fmt/chrono.h>
+
+#include "fuzzer-common.h"
+
+template <typename Period, typename Rep>
+void invoke_inner(fmt::string_view format_str, Rep rep) {
+  auto value = std::chrono::duration<Rep, Period>(rep);
+  try {
+#if FMT_FUZZ_FORMAT_TO_STRING
+    std::string message = fmt::format(format_str, value);
+#else
+    fmt::memory_buffer buf;
+    fmt::format_to(buf, format_str, value);
+#endif
+  } catch (std::exception&) {
+  }
+}
+
+// Rep is a duration's representation type.
+template <typename Rep>
+void invoke_outer(const uint8_t* data, size_t size, int period) {
+  // Always use a fixed location of the data.
+  static_assert(sizeof(Rep) <= fixed_size, "fixed size is too small");
+  if (size <= fixed_size + 1) return;
+
+  const Rep rep = assign_from_buf<Rep>(data);
+  data += fixed_size;
+  size -= fixed_size;
+
+  // data is already allocated separately in libFuzzer so reading past the end 
+  // will most likely be detected anyway.
+  const auto format_str = fmt::string_view(as_chars(data), size);
+
+  // yocto, zepto, zetta and yotta are not handled.
+  switch (period) {
+  case 1:
+    invoke_inner<std::atto>(format_str, rep);
+    break;
+  case 2:
+    invoke_inner<std::femto>(format_str, rep);
+    break;
+  case 3:
+    invoke_inner<std::pico>(format_str, rep);
+    break;
+  case 4:
+    invoke_inner<std::nano>(format_str, rep);
+    break;
+  case 5:
+    invoke_inner<std::micro>(format_str, rep);
+    break;
+  case 6:
+    invoke_inner<std::milli>(format_str, rep);
+    break;
+  case 7:
+    invoke_inner<std::centi>(format_str, rep);
+    break;
+  case 8:
+    invoke_inner<std::deci>(format_str, rep);
+    break;
+  case 9:
+    invoke_inner<std::deca>(format_str, rep);
+    break;
+  case 10:
+    invoke_inner<std::kilo>(format_str, rep);
+    break;
+  case 11:
+    invoke_inner<std::mega>(format_str, rep);
+    break;
+  case 12:
+    invoke_inner<std::giga>(format_str, rep);
+    break;
+  case 13:
+    invoke_inner<std::tera>(format_str, rep);
+    break;
+  case 14:
+    invoke_inner<std::peta>(format_str, rep);
+    break;
+  case 15:
+    invoke_inner<std::exa>(format_str, rep);
+    break;
+  }
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size <= 4)  return 0;
+
+  const auto representation = data[0];
+  const auto period = data[1];
+  data += 2;
+  size -= 2;
+
+  switch (representation) {
+  case 1:
+    invoke_outer<char>(data, size, period);
+    break;
+  case 2:
+    invoke_outer<signed char>(data, size, period);
+    break;
+  case 3:
+    invoke_outer<unsigned char>(data, size, period);
+    break;
+  case 4:
+    invoke_outer<short>(data, size, period);
+    break;
+  case 5:
+    invoke_outer<unsigned short>(data, size, period);
+    break;
+  case 6:
+    invoke_outer<int>(data, size, period);
+    break;
+  case 7:
+    invoke_outer<unsigned int>(data, size, period);
+    break;
+  case 8:
+    invoke_outer<long>(data, size, period);
+    break;
+  case 9:
+    invoke_outer<unsigned long>(data, size, period);
+    break;
+  case 10:
+    invoke_outer<float>(data, size, period);
+    break;
+  case 11:
+    invoke_outer<double>(data, size, period);
+    break;
+  case 12:
+    invoke_outer<long double>(data, size, period);
+    break;
+  }
+  return 0;
+}
diff --git a/test/fuzzing/chrono_duration.cpp b/test/fuzzing/chrono_duration.cpp
deleted file mode 100644
index d1de9ae..0000000
--- a/test/fuzzing/chrono_duration.cpp
+++ /dev/null
@@ -1,152 +0,0 @@
-// Copyright (c) 2019, Paul Dreik
-// License: see LICENSE.rst in the fmt root directory
-
-#include <fmt/chrono.h>
-#include <cstdint>
-#include <limits>
-#include <stdexcept>
-#include <type_traits>
-#include <vector>
-#include "fuzzer_common.h"
-
-template <typename Item, typename Ratio>
-void invoke_inner(fmt::string_view formatstring, const Item item) {
-  const std::chrono::duration<Item, Ratio> value(item);
-  try {
-#if FMT_FUZZ_FORMAT_TO_STRING
-    std::string message = fmt::format(formatstring, value);
-#else
-    fmt::memory_buffer buf;
-    fmt::format_to(buf, formatstring, value);
-#endif
-  } catch (std::exception& /*e*/) {
-  }
-}
-
-// Item is the underlying type for duration (int, long etc)
-template <typename Item>
-void invoke_outer(const uint8_t* Data, std::size_t Size, const int scaling) {
-  // always use a fixed location of the data
-  using fmt_fuzzer::Nfixed;
-
-  constexpr auto N = sizeof(Item);
-  static_assert(N <= Nfixed, "fixed size is too small");
-  if (Size <= Nfixed + 1) {
-    return;
-  }
-
-  const Item item = fmt_fuzzer::assignFromBuf<Item>(Data);
-
-  // fast forward
-  Data += Nfixed;
-  Size -= Nfixed;
-
-  // Data is already allocated separately in libFuzzer so reading past
-  // the end will most likely be detected anyway
-  const auto formatstring = fmt::string_view(fmt_fuzzer::as_chars(Data), Size);
-
-  // doit_impl<Item,std::yocto>(buf.data(),item);
-  // doit_impl<Item,std::zepto>(buf.data(),item);
-  switch (scaling) {
-  case 1:
-    invoke_inner<Item, std::atto>(formatstring, item);
-    break;
-  case 2:
-    invoke_inner<Item, std::femto>(formatstring, item);
-    break;
-  case 3:
-    invoke_inner<Item, std::pico>(formatstring, item);
-    break;
-  case 4:
-    invoke_inner<Item, std::nano>(formatstring, item);
-    break;
-  case 5:
-    invoke_inner<Item, std::micro>(formatstring, item);
-    break;
-  case 6:
-    invoke_inner<Item, std::milli>(formatstring, item);
-    break;
-  case 7:
-    invoke_inner<Item, std::centi>(formatstring, item);
-    break;
-  case 8:
-    invoke_inner<Item, std::deci>(formatstring, item);
-    break;
-  case 9:
-    invoke_inner<Item, std::deca>(formatstring, item);
-    break;
-  case 10:
-    invoke_inner<Item, std::kilo>(formatstring, item);
-    break;
-  case 11:
-    invoke_inner<Item, std::mega>(formatstring, item);
-    break;
-  case 12:
-    invoke_inner<Item, std::giga>(formatstring, item);
-    break;
-  case 13:
-    invoke_inner<Item, std::tera>(formatstring, item);
-    break;
-  case 14:
-    invoke_inner<Item, std::peta>(formatstring, item);
-    break;
-  case 15:
-    invoke_inner<Item, std::exa>(formatstring, item);
-  }
-  // doit_impl<Item,std::zeta>(buf.data(),item);
-  // doit_impl<Item,std::yotta>(buf.data(),item);
-}
-
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
-  if (Size <= 4) {
-    return 0;
-  }
-
-  const auto representation = Data[0];
-  const auto scaling = Data[1];
-  Data += 2;
-  Size -= 2;
-
-  switch (representation) {
-  case 1:
-    invoke_outer<char>(Data, Size, scaling);
-    break;
-  case 2:
-    invoke_outer<unsigned char>(Data, Size, scaling);
-    break;
-  case 3:
-    invoke_outer<signed char>(Data, Size, scaling);
-    break;
-  case 4:
-    invoke_outer<short>(Data, Size, scaling);
-    break;
-  case 5:
-    invoke_outer<unsigned short>(Data, Size, scaling);
-    break;
-  case 6:
-    invoke_outer<int>(Data, Size, scaling);
-    break;
-  case 7:
-    invoke_outer<unsigned int>(Data, Size, scaling);
-    break;
-  case 8:
-    invoke_outer<long>(Data, Size, scaling);
-    break;
-  case 9:
-    invoke_outer<unsigned long>(Data, Size, scaling);
-    break;
-  case 10:
-    invoke_outer<float>(Data, Size, scaling);
-    break;
-  case 11:
-    invoke_outer<double>(Data, Size, scaling);
-    break;
-  case 12:
-    invoke_outer<long double>(Data, Size, scaling);
-    break;
-  default:
-    break;
-  }
-
-  return 0;
-}
diff --git a/test/fuzzing/float.cc b/test/fuzzing/float.cc
new file mode 100644
index 0000000..a9a347e
--- /dev/null
+++ b/test/fuzzing/float.cc
@@ -0,0 +1,34 @@
+// A fuzzer for floating-point formatter.
+// For the license information refer to format.h.
+
+#include <cstdint>
+#include <cstdlib>
+#include <stdexcept>
+#include <limits>
+#include <fmt/format.h>
+
+#include "fuzzer-common.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size <= sizeof(double) || !std::numeric_limits<double>::is_iec559)
+    return 0;
+
+  auto value = assign_from_buf<double>(data);
+  auto buffer = fmt::memory_buffer();
+  fmt::format_to(buffer, "{}", value);
+
+  // Check a round trip.
+  if (std::isnan(value)) {
+    auto nan = std::signbit(value) ? "-nan" : "nan";
+    if (fmt::string_view(buffer.data(), buffer.size()) != nan)
+      throw std::runtime_error("round trip failure");
+    return 0;
+  }
+  buffer.push_back('\0');
+  char* ptr = nullptr;
+  if (std::strtod(buffer.data(), &ptr) != value)
+    throw std::runtime_error("round trip failure");
+  if (ptr + 1 != buffer.end())
+    throw std::runtime_error("unparsed output");
+  return 0;
+}
diff --git a/test/fuzzing/fuzzer-common.h b/test/fuzzing/fuzzer-common.h
new file mode 100644
index 0000000..635a5d9
--- /dev/null
+++ b/test/fuzzing/fuzzer-common.h
@@ -0,0 +1,75 @@
+// Copyright (c) 2019, Paul Dreik
+// For the license information refer to format.h.
+
+#ifndef FUZZER_COMMON_H
+#define FUZZER_COMMON_H
+
+#include <cstdint>      // std::uint8_t
+#include <cstring>      // memcpy
+#include <vector>
+
+#include <fmt/core.h>
+
+// One can format to either a string, or a buffer. The latter is faster, but
+// one may be interested in formatting to a string instead to verify it works
+// as intended. To avoid a combinatoric explosion, select this at compile time
+// instead of dynamically from the fuzz data.
+#define FMT_FUZZ_FORMAT_TO_STRING 0
+
+// If {fmt} is given a buffer that is separately allocated, chances that address
+// sanitizer detects out of bound reads is much higher. However, it slows down
+// the fuzzing.
+#define FMT_FUZZ_SEPARATE_ALLOCATION 1
+
+// The size of the largest possible type in use.
+// To let the the fuzzer mutation be efficient at cross pollinating between
+// different types, use a fixed size format. The same bit pattern, interpreted
+// as another type, is likely interesting.
+constexpr auto fixed_size = 16;
+
+// Casts data to a char pointer.
+template <typename T> inline const char* as_chars(const T* data) {
+  return reinterpret_cast<const char*>(data);
+}
+
+// Casts data to a byte pointer.
+template <typename T> inline const std::uint8_t* as_bytes(const T* data) {
+  return reinterpret_cast<const std::uint8_t*>(data);
+}
+
+// Blits bytes from data to form an (assumed trivially constructible) object
+// of type Item.
+template <class Item> inline Item assign_from_buf(const std::uint8_t* data) {
+  auto item = Item();
+  std::memcpy(&item, data, sizeof(Item));
+  return item;
+}
+
+// Reads a boolean value by looking at the first byte from data.
+template <> inline bool assign_from_buf<bool>(const std::uint8_t* data) {
+  return *data != 0;
+}
+
+struct data_to_string {
+#if FMT_FUZZ_SEPARATE_ALLOCATION
+  std::vector<char> buffer;
+
+  data_to_string(const uint8_t* data, size_t size, bool add_terminator = false)
+      : buffer(size + (add_terminator ? 1 : 0)) {
+    std::memcpy(buffer.data(), data, size);
+  }
+
+  fmt::string_view get() const { return {buffer.data(), buffer.size()}; }
+#else
+  fmt::string_view sv;
+
+  data_to_string(const uint8_t* data, size_t size, bool = false)
+      : str(as_chars(data), size) {}
+
+  fmt::string_view get() const { return sv; }
+#endif
+
+  const char* data() const { return get().data(); }
+};
+
+#endif  // FUZZER_COMMON_H
diff --git a/test/fuzzing/fuzzer_common.h b/test/fuzzing/fuzzer_common.h
deleted file mode 100644
index c3d8561..0000000
--- a/test/fuzzing/fuzzer_common.h
+++ /dev/null
@@ -1,67 +0,0 @@
-#ifndef FUZZER_COMMON_H
-#define FUZZER_COMMON_H
-
-// Copyright (c) 2019, Paul Dreik
-// License: see LICENSE.rst in the fmt root directory
-
-#include <cstdint>      // std::uint8_t
-#include <cstring>      // memcpy
-#include <type_traits>  // trivially copyable
-
-// one can format to either a string, or a buf. buf is faster,
-// but one may be interested in formatting to a string instead to
-// verify it works as intended. to avoid a combinatoric explosion,
-// select this at compile time instead of dynamically from the fuzz data
-#define FMT_FUZZ_FORMAT_TO_STRING 0
-
-// if fmt is given a buffer that is separately allocated,
-// chances that address sanitizer detects out of bound reads is
-// much higher. However, it slows down the fuzzing.
-#define FMT_FUZZ_SEPARATE_ALLOCATION 1
-
-// To let the the fuzzer mutation be efficient at cross pollinating
-// between different types, use a fixed size format.
-// The same bit pattern, interpreted as another type,
-// is likely interesting.
-// For this, we must know the size of the largest possible type in use.
-
-// There are some problems on travis, claiming Nfixed is not a constant
-// expression which seems to be an issue with older versions of libstdc++
-#if _GLIBCXX_RELEASE >= 7
-#  include <algorithm>
-namespace fmt_fuzzer {
-constexpr auto Nfixed = std::max(sizeof(long double), sizeof(std::intmax_t));
-}
-#else
-namespace fmt_fuzzer {
-constexpr auto Nfixed = 16;
-}
-#endif
-
-namespace fmt_fuzzer {
-// view data as a c char pointer.
-template <typename T> inline const char* as_chars(const T* data) {
-  return static_cast<const char*>(static_cast<const void*>(data));
-}
-
-// view data as a byte pointer
-template <typename T> inline const std::uint8_t* as_bytes(const T* data) {
-  return static_cast<const std::uint8_t*>(static_cast<const void*>(data));
-}
-
-// blits bytes from Data to form an (assumed trivially constructible) object
-// of type Item
-template <class Item> inline Item assignFromBuf(const std::uint8_t* Data) {
-  Item item{};
-  std::memcpy(&item, Data, sizeof(Item));
-  return item;
-}
-
-// reads a boolean value by looking at the first byte from Data
-template <> inline bool assignFromBuf<bool>(const std::uint8_t* Data) {
-  return !!Data[0];
-}
-
-}  // namespace fmt_fuzzer
-
-#endif  // FUZZER_COMMON_H
diff --git a/test/fuzzing/main.cc b/test/fuzzing/main.cc
new file mode 100644
index 0000000..8f8c719
--- /dev/null
+++ b/test/fuzzing/main.cc
@@ -0,0 +1,22 @@
+#include <cassert>
+#include <fstream>
+#include <vector>
+
+#include "fuzzer-common.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
+
+int main(int argc, char** argv) {
+  for (int i = 1; i < argc; ++i) {
+    std::ifstream in(argv[i]);
+    assert(in);
+    in.seekg(0, std::ios_base::end);
+    const auto size = in.tellg();
+    assert(size >= 0);
+    in.seekg(0, std::ios_base::beg);
+    std::vector<char> buf(static_cast<size_t>(size));
+    in.read(buf.data(), size);
+    assert(in.gcount() == size);
+    LLVMFuzzerTestOneInput(as_bytes(buf.data()), buf.size());
+  }
+}
diff --git a/test/fuzzing/main.cpp b/test/fuzzing/main.cpp
deleted file mode 100644
index 6ac8130..0000000
--- a/test/fuzzing/main.cpp
+++ /dev/null
@@ -1,21 +0,0 @@
-#include <cassert>
-#include <fstream>
-#include <sstream>
-#include <vector>
-#include "fuzzer_common.h"
-
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size);
-int main(int argc, char* argv[]) {
-  for (int i = 1; i < argc; ++i) {
-    std::ifstream in(argv[i]);
-    assert(in);
-    in.seekg(0, std::ios_base::end);
-    const auto pos = in.tellg();
-    assert(pos >= 0);
-    in.seekg(0, std::ios_base::beg);
-    std::vector<char> buf(static_cast<std::size_t>(pos));
-    in.read(buf.data(), static_cast<long>(buf.size()));
-    assert(in.gcount() == pos);
-    LLVMFuzzerTestOneInput(fmt_fuzzer::as_bytes(buf.data()), buf.size());
-  }
-}
diff --git a/test/fuzzing/named-arg.cc b/test/fuzzing/named-arg.cc
new file mode 100644
index 0000000..ffd8e90
--- /dev/null
+++ b/test/fuzzing/named-arg.cc
@@ -0,0 +1,100 @@
+// Copyright (c) 2019, Paul Dreik
+// For the license information refer to format.h.
+
+#include <cstdint>
+#include <type_traits>
+#include <vector>
+#include <fmt/chrono.h>
+
+#include "fuzzer-common.h"
+
+template <typename T>
+void invoke_fmt(const uint8_t* data, size_t size, unsigned arg_name_size) {
+  static_assert(sizeof(T) <= fixed_size, "fixed_size too small");
+  if (size <= fixed_size) return;
+  const T value = assign_from_buf<T>(data);
+  data += fixed_size;
+  size -= fixed_size;
+
+  if (arg_name_size <= 0 || arg_name_size >= size) return;
+  data_to_string arg_name(data, arg_name_size, true);
+  data += arg_name_size;
+  size -= arg_name_size;
+
+  data_to_string format_str(data, size);
+  try {
+#if FMT_FUZZ_FORMAT_TO_STRING
+    std::string message =
+      fmt::format(format_str.get(), fmt::arg(arg_name.data(), value));
+#else
+    fmt::memory_buffer out;
+    fmt::format_to(out, format_str.get(), fmt::arg(arg_name.data(), value));
+#endif
+  } catch (std::exception&) {
+  }
+}
+
+// For dynamic dispatching to an explicit instantiation.
+template <typename Callback> void invoke(int type, Callback callback) {
+  switch (type) {
+  case 0:
+    callback(bool());
+    break;
+  case 1:
+    callback(char());
+    break;
+  case 2:
+    using sc = signed char;
+    callback(sc());
+    break;
+  case 3:
+    using uc = unsigned char;
+    callback(uc());
+    break;
+  case 4:
+    callback(short());
+    break;
+  case 5:
+    using us = unsigned short;
+    callback(us());
+    break;
+  case 6:
+    callback(int());
+    break;
+  case 7:
+    callback(unsigned());
+    break;
+  case 8:
+    callback(long());
+    break;
+  case 9:
+    using ul = unsigned long;
+    callback(ul());
+    break;
+  case 10:
+    callback(float());
+    break;
+  case 11:
+    callback(double());
+    break;
+  case 12:
+    using LD = long double;
+    callback(LD());
+    break;
+  }
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size <= 3) return 0;
+
+  // Switch types depending on the first byte of the input.
+  const auto type = data[0] & 0x0F;
+  const unsigned arg_name_size = (data[0] & 0xF0) >> 4;
+  data++;
+  size--;
+
+  invoke(type, [=](auto arg) {
+    invoke_fmt<decltype(arg)>(data, size, arg_name_size);
+  });
+  return 0;
+}
diff --git a/test/fuzzing/named_arg.cpp b/test/fuzzing/named_arg.cpp
deleted file mode 100644
index 0f9a451..0000000
--- a/test/fuzzing/named_arg.cpp
+++ /dev/null
@@ -1,128 +0,0 @@
-// Copyright (c) 2019, Paul Dreik
-// License: see LICENSE.rst in the fmt root directory
-
-#include <fmt/chrono.h>
-#include <fmt/core.h>
-#include <cstdint>
-#include <stdexcept>
-#include <type_traits>
-#include <vector>
-#include "fuzzer_common.h"
-
-template <typename Item1>
-void invoke_fmt(const uint8_t* Data, std::size_t Size, unsigned int argsize) {
-  constexpr auto N1 = sizeof(Item1);
-  static_assert(N1 <= fmt_fuzzer::Nfixed, "Nfixed too small");
-  if (Size <= fmt_fuzzer::Nfixed) {
-    return;
-  }
-  const Item1 item1 = fmt_fuzzer::assignFromBuf<Item1>(Data);
-
-  Data += fmt_fuzzer::Nfixed;
-  Size -= fmt_fuzzer::Nfixed;
-
-  // how many chars should be used for the argument name?
-  if (argsize <= 0 || argsize >= Size) {
-    return;
-  }
-
-  // allocating buffers separately is slower, but increases chances
-  // of detecting memory errors
-#if FMT_FUZZ_SEPARATE_ALLOCATION
-  std::vector<char> argnamebuffer(argsize);
-  std::memcpy(argnamebuffer.data(), Data, argsize);
-  auto argname = fmt::string_view(argnamebuffer.data(), argsize);
-#else
-  auto argname = fmt::string_view(fmt_fuzzer::as_chars(Data), argsize);
-#endif
-  Data += argsize;
-  Size -= argsize;
-
-#if FMT_FUZZ_SEPARATE_ALLOCATION
-  // allocates as tight as possible, making it easier to catch buffer overruns.
-  std::vector<char> fmtstringbuffer(Size);
-  std::memcpy(fmtstringbuffer.data(), Data, Size);
-  auto fmtstring = fmt::string_view(fmtstringbuffer.data(), Size);
-#else
-  auto fmtstring = fmt::string_view(fmt_fuzzer::as_chars(Data), Size);
-#endif
-
-#if FMT_FUZZ_FORMAT_TO_STRING
-  std::string message = fmt::format(fmtstring, fmt::arg(argname, item1));
-#else
-  fmt::memory_buffer outbuf;
-  fmt::format_to(outbuf, fmtstring, fmt::arg(argname, item1));
-#endif
-}
-
-// for dynamic dispatching to an explicit instantiation
-template <typename Callback> void invoke(int index, Callback callback) {
-  switch (index) {
-  case 0:
-    callback(bool{});
-    break;
-  case 1:
-    callback(char{});
-    break;
-  case 2:
-    using sc = signed char;
-    callback(sc{});
-    break;
-  case 3:
-    using uc = unsigned char;
-    callback(uc{});
-    break;
-  case 4:
-    callback(short{});
-    break;
-  case 5:
-    using us = unsigned short;
-    callback(us{});
-    break;
-  case 6:
-    callback(int{});
-    break;
-  case 7:
-    callback(unsigned{});
-    break;
-  case 8:
-    callback(long{});
-    break;
-  case 9:
-    using ul = unsigned long;
-    callback(ul{});
-    break;
-  case 10:
-    callback(float{});
-    break;
-  case 11:
-    callback(double{});
-    break;
-  case 12:
-    using LD = long double;
-    callback(LD{});
-    break;
-  }
-}
-
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
-  if (Size <= 3) {
-    return 0;
-  }
-
-  // switch types depending on the first byte of the input
-  const auto first = Data[0] & 0x0F;
-  const unsigned int second = (Data[0] & 0xF0) >> 4;
-  Data++;
-  Size--;
-
-  auto outerfcn = [=](auto param1) {
-    invoke_fmt<decltype(param1)>(Data, Size, second);
-  };
-
-  try {
-    invoke(first, outerfcn);
-  } catch (std::exception& /*e*/) {
-  }
-  return 0;
-}
diff --git a/test/fuzzing/one-arg.cc b/test/fuzzing/one-arg.cc
new file mode 100644
index 0000000..df17343
--- /dev/null
+++ b/test/fuzzing/one-arg.cc
@@ -0,0 +1,91 @@
+// Copyright (c) 2019, Paul Dreik
+// For the license information refer to format.h.
+
+#include <cstdint>
+#include <exception>
+#include <fmt/chrono.h>
+
+#include "fuzzer-common.h"
+
+template <typename T, typename Repr>
+const T* from_repr(const Repr& r) { return &r; }
+
+template <>
+const std::tm* from_repr<std::tm>(const std::time_t& t) {
+  return std::localtime(&t);
+}
+
+template <typename T, typename Repr = T>
+void invoke_fmt(const uint8_t* data, size_t size) {
+  static_assert(sizeof(Repr) <= fixed_size, "Nfixed is too small");
+  if (size <= fixed_size) return;
+  auto repr = assign_from_buf<Repr>(data);
+  const T* value = from_repr<T>(repr);
+  if (!value) return;
+  data += fixed_size;
+  size -= fixed_size;
+  data_to_string format_str(data, size);
+  try {
+#if FMT_FUZZ_FORMAT_TO_STRING
+    std::string message = fmt::format(format_str.get(), *value);
+#else
+    fmt::memory_buffer message;
+    fmt::format_to(message, format_str.get(), *value);
+#endif
+  } catch (std::exception&) {
+  }
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size <= 3) return 0;
+
+  const auto first = data[0];
+  data++;
+  size--;
+
+  switch (first) {
+  case 0:
+    invoke_fmt<bool>(data, size);
+    break;
+  case 1:
+    invoke_fmt<char>(data, size);
+    break;
+  case 2:
+    invoke_fmt<unsigned char>(data, size);
+    break;
+  case 3:
+    invoke_fmt<signed char>(data, size);
+    break;
+  case 4:
+    invoke_fmt<short>(data, size);
+    break;
+  case 5:
+    invoke_fmt<unsigned short>(data, size);
+    break;
+  case 6:
+    invoke_fmt<int>(data, size);
+    break;
+  case 7:
+    invoke_fmt<unsigned int>(data, size);
+    break;
+  case 8:
+    invoke_fmt<long>(data, size);
+    break;
+  case 9:
+    invoke_fmt<unsigned long>(data, size);
+    break;
+  case 10:
+    invoke_fmt<float>(data, size);
+    break;
+  case 11:
+    invoke_fmt<double>(data, size);
+    break;
+  case 12:
+    invoke_fmt<long double>(data, size);
+    break;
+  case 13:
+    invoke_fmt<std::tm, std::time_t>(data, size);
+    break;
+  }
+  return 0;
+}
diff --git a/test/fuzzing/one_arg.cpp b/test/fuzzing/one_arg.cpp
deleted file mode 100644
index 86a159b..0000000
--- a/test/fuzzing/one_arg.cpp
+++ /dev/null
@@ -1,131 +0,0 @@
-// Copyright (c) 2019, Paul Dreik
-// License: see LICENSE.rst in the fmt root directory
-
-#include <fmt/core.h>
-#include <cstdint>
-#include <stdexcept>
-#include <type_traits>
-#include <vector>
-
-#include <fmt/chrono.h>
-#include "fuzzer_common.h"
-
-using fmt_fuzzer::Nfixed;
-
-template <typename Item>
-void invoke_fmt(const uint8_t* Data, std::size_t Size) {
-  constexpr auto N = sizeof(Item);
-  static_assert(N <= Nfixed, "Nfixed is too small");
-  if (Size <= Nfixed) {
-    return;
-  }
-  const Item item = fmt_fuzzer::assignFromBuf<Item>(Data);
-  Data += Nfixed;
-  Size -= Nfixed;
-
-#if FMT_FUZZ_SEPARATE_ALLOCATION
-  // allocates as tight as possible, making it easier to catch buffer overruns.
-  std::vector<char> fmtstringbuffer(Size);
-  std::memcpy(fmtstringbuffer.data(), Data, Size);
-  auto fmtstring = fmt::string_view(fmtstringbuffer.data(), Size);
-#else
-  auto fmtstring = fmt::string_view(fmt_fuzzer::as_chars(Data), Size);
-#endif
-
-#if FMT_FUZZ_FORMAT_TO_STRING
-  std::string message = fmt::format(fmtstring, item);
-#else
-  fmt::memory_buffer message;
-  fmt::format_to(message, fmtstring, item);
-#endif
-}
-
-void invoke_fmt_time(const uint8_t* Data, std::size_t Size) {
-  using Item = std::time_t;
-  constexpr auto N = sizeof(Item);
-  static_assert(N <= Nfixed, "Nfixed too small");
-  if (Size <= Nfixed) {
-    return;
-  }
-  const Item item = fmt_fuzzer::assignFromBuf<Item>(Data);
-  Data += Nfixed;
-  Size -= Nfixed;
-#if FMT_FUZZ_SEPARATE_ALLOCATION
-  // allocates as tight as possible, making it easier to catch buffer overruns.
-  std::vector<char> fmtstringbuffer(Size);
-  std::memcpy(fmtstringbuffer.data(), Data, Size);
-  auto fmtstring = fmt::string_view(fmtstringbuffer.data(), Size);
-#else
-  auto fmtstring = fmt::string_view(fmt_fuzzer::as_chars(Data), Size);
-#endif
-  auto* b = std::localtime(&item);
-  if (b) {
-#if FMT_FUZZ_FORMAT_TO_STRING
-    std::string message = fmt::format(fmtstring, *b);
-#else
-    fmt::memory_buffer message;
-    fmt::format_to(message, fmtstring, *b);
-#endif
-  }
-}
-
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
-  if (Size <= 3) {
-    return 0;
-  }
-
-  const auto first = Data[0];
-  Data++;
-  Size--;
-
-  try {
-    switch (first) {
-    case 0:
-      invoke_fmt<bool>(Data, Size);
-      break;
-    case 1:
-      invoke_fmt<char>(Data, Size);
-      break;
-    case 2:
-      invoke_fmt<unsigned char>(Data, Size);
-      break;
-    case 3:
-      invoke_fmt<signed char>(Data, Size);
-      break;
-    case 4:
-      invoke_fmt<short>(Data, Size);
-      break;
-    case 5:
-      invoke_fmt<unsigned short>(Data, Size);
-      break;
-    case 6:
-      invoke_fmt<int>(Data, Size);
-      break;
-    case 7:
-      invoke_fmt<unsigned int>(Data, Size);
-      break;
-    case 8:
-      invoke_fmt<long>(Data, Size);
-      break;
-    case 9:
-      invoke_fmt<unsigned long>(Data, Size);
-      break;
-    case 10:
-      invoke_fmt<float>(Data, Size);
-      break;
-    case 11:
-      invoke_fmt<double>(Data, Size);
-      break;
-    case 12:
-      invoke_fmt<long double>(Data, Size);
-      break;
-    case 13:
-      invoke_fmt_time(Data, Size);
-      break;
-    default:
-      break;
-    }
-  } catch (std::exception& /*e*/) {
-  }
-  return 0;
-}
diff --git a/test/fuzzing/sprintf.cpp b/test/fuzzing/sprintf.cpp
deleted file mode 100644
index 7dd0222..0000000
--- a/test/fuzzing/sprintf.cpp
+++ /dev/null
@@ -1,116 +0,0 @@
-// Copyright (c) 2019, Paul Dreik
-// License: see LICENSE.rst in the fmt root directory
-#include <fmt/format.h>
-#include <fmt/printf.h>
-#include <cstdint>
-#include <stdexcept>
-
-#include "fuzzer_common.h"
-
-using fmt_fuzzer::Nfixed;
-
-template <typename Item1, typename Item2>
-void invoke_fmt(const uint8_t* Data, std::size_t Size) {
-  constexpr auto N1 = sizeof(Item1);
-  constexpr auto N2 = sizeof(Item2);
-  static_assert(N1 <= Nfixed, "size1 exceeded");
-  static_assert(N2 <= Nfixed, "size2 exceeded");
-  if (Size <= Nfixed + Nfixed) {
-    return;
-  }
-  Item1 item1 = fmt_fuzzer::assignFromBuf<Item1>(Data);
-  Data += Nfixed;
-  Size -= Nfixed;
-
-  Item2 item2 = fmt_fuzzer::assignFromBuf<Item2>(Data);
-  Data += Nfixed;
-  Size -= Nfixed;
-
-  auto fmtstring = fmt::string_view(fmt_fuzzer::as_chars(Data), Size);
-
-#if FMT_FUZZ_FORMAT_TO_STRING
-  std::string message = fmt::format(fmtstring, item1, item2);
-#else
-  fmt::memory_buffer message;
-  fmt::format_to(message, fmtstring, item1, item2);
-#endif
-}
-
-// for dynamic dispatching to an explicit instantiation
-template <typename Callback> void invoke(int index, Callback callback) {
-  switch (index) {
-  case 0:
-    callback(bool{});
-    break;
-  case 1:
-    callback(char{});
-    break;
-  case 2:
-    using sc = signed char;
-    callback(sc{});
-    break;
-  case 3:
-    using uc = unsigned char;
-    callback(uc{});
-    break;
-  case 4:
-    callback(short{});
-    break;
-  case 5:
-    using us = unsigned short;
-    callback(us{});
-    break;
-  case 6:
-    callback(int{});
-    break;
-  case 7:
-    callback(unsigned{});
-    break;
-  case 8:
-    callback(long{});
-    break;
-  case 9:
-    using ul = unsigned long;
-    callback(ul{});
-    break;
-  case 10:
-    callback(float{});
-    break;
-  case 11:
-    callback(double{});
-    break;
-  case 12:
-    using LD = long double;
-    callback(LD{});
-    break;
-  case 13:
-    using ptr = void*;
-    callback(ptr{});
-    break;
-  }
-}
-
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
-  if (Size <= 3) {
-    return 0;
-  }
-
-  // switch types depending on the first byte of the input
-  const auto first = Data[0] & 0x0F;
-  const auto second = (Data[0] & 0xF0) >> 4;
-  Data++;
-  Size--;
-
-  auto outer = [=](auto param1) {
-    auto inner = [=](auto param2) {
-      invoke_fmt<decltype(param1), decltype(param2)>(Data, Size);
-    };
-    invoke(second, inner);
-  };
-
-  try {
-    invoke(first, outer);
-  } catch (std::exception& /*e*/) {
-  }
-  return 0;
-}
diff --git a/test/fuzzing/two-args.cc b/test/fuzzing/two-args.cc
new file mode 100644
index 0000000..4d7d345
--- /dev/null
+++ b/test/fuzzing/two-args.cc
@@ -0,0 +1,105 @@
+// Copyright (c) 2019, Paul Dreik
+// For the license information refer to format.h.
+
+#include <cstdint>
+#include <exception>
+#include <string>
+#include <fmt/format.h>
+
+#include "fuzzer-common.h"
+
+template <typename Item1, typename Item2>
+void invoke_fmt(const uint8_t* data, size_t size) {
+  static_assert(sizeof(Item1) <= fixed_size, "size1 exceeded");
+  static_assert(sizeof(Item2) <= fixed_size, "size2 exceeded");
+  if (size <= fixed_size + fixed_size) return;
+
+  const Item1 item1 = assign_from_buf<Item1>(data);
+  data += fixed_size;
+  size -= fixed_size;
+
+  const Item2 item2 = assign_from_buf<Item2>(data);
+  data += fixed_size;
+  size -= fixed_size;
+
+  auto format_str = fmt::string_view(as_chars(data), size);
+#if FMT_FUZZ_FORMAT_TO_STRING
+  std::string message = fmt::format(format_str, item1, item2);
+#else
+  fmt::memory_buffer message;
+  fmt::format_to(message, format_str, item1, item2);
+#endif
+}
+
+// For dynamic dispatching to an explicit instantiation.
+template <typename Callback> void invoke(int index, Callback callback) {
+  switch (index) {
+  case 0:
+    callback(bool());
+    break;
+  case 1:
+    callback(char());
+    break;
+  case 2:
+    using sc = signed char;
+    callback(sc());
+    break;
+  case 3:
+    using uc = unsigned char;
+    callback(uc());
+    break;
+  case 4:
+    callback(short());
+    break;
+  case 5:
+    using us = unsigned short;
+    callback(us());
+    break;
+  case 6:
+    callback(int());
+    break;
+  case 7:
+    callback(unsigned());
+    break;
+  case 8:
+    callback(long());
+    break;
+  case 9:
+    using ul = unsigned long;
+    callback(ul());
+    break;
+  case 10:
+    callback(float());
+    break;
+  case 11:
+    callback(double());
+    break;
+  case 12:
+    using LD = long double;
+    callback(LD());
+    break;
+  case 13:
+    using ptr = void*;
+    callback(ptr());
+    break;
+  }
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size <= 3) return 0;
+
+  // Switch types depending on the first byte of the input.
+  const auto type1 = data[0] & 0x0F;
+  const auto type2 = (data[0] & 0xF0) >> 4;
+  data++;
+  size--;
+  try {
+    invoke(type1, [=](auto param1) {
+      invoke(type2, [=](auto param2) {
+        invoke_fmt<decltype(param1), decltype(param2)>(data, size);
+      });
+    });
+  } catch (std::exception&) {
+  }
+  return 0;
+}
diff --git a/test/fuzzing/two_args.cpp b/test/fuzzing/two_args.cpp
deleted file mode 100644
index 72b035c..0000000
--- a/test/fuzzing/two_args.cpp
+++ /dev/null
@@ -1,112 +0,0 @@
-// Copyright (c) 2019, Paul Dreik
-// License: see LICENSE.rst in the fmt root directory
-#include <fmt/format.h>
-#include <cstdint>
-#include <stdexcept>
-#include <type_traits>
-
-#include "fuzzer_common.h"
-
-constexpr auto Nfixed = fmt_fuzzer::Nfixed;
-
-template <typename Item1, typename Item2>
-void invoke_fmt(const uint8_t* Data, std::size_t Size) {
-  constexpr auto N1 = sizeof(Item1);
-  constexpr auto N2 = sizeof(Item2);
-  static_assert(N1 <= Nfixed, "size1 exceeded");
-  static_assert(N2 <= Nfixed, "size2 exceeded");
-  if (Size <= Nfixed + Nfixed) {
-    return;
-  }
-  const Item1 item1 = fmt_fuzzer::assignFromBuf<Item1>(Data);
-  Data += Nfixed;
-  Size -= Nfixed;
-
-  const Item2 item2 = fmt_fuzzer::assignFromBuf<Item2>(Data);
-  Data += Nfixed;
-  Size -= Nfixed;
-
-  auto fmtstring = fmt::string_view(fmt_fuzzer::as_chars(Data), Size);
-
-#if FMT_FUZZ_FORMAT_TO_STRING
-  std::string message = fmt::format(fmtstring, item1, item2);
-#else
-  fmt::memory_buffer message;
-  fmt::format_to(message, fmtstring, item1, item2);
-#endif
-}
-
-// for dynamic dispatching to an explicit instantiation
-template <typename Callback> void invoke(int index, Callback callback) {
-  switch (index) {
-  case 0:
-    callback(bool{});
-    break;
-  case 1:
-    callback(char{});
-    break;
-  case 2:
-    using sc = signed char;
-    callback(sc{});
-    break;
-  case 3:
-    using uc = unsigned char;
-    callback(uc{});
-    break;
-  case 4:
-    callback(short{});
-    break;
-  case 5:
-    using us = unsigned short;
-    callback(us{});
-    break;
-  case 6:
-    callback(int{});
-    break;
-  case 7:
-    callback(unsigned{});
-    break;
-  case 8:
-    callback(long{});
-    break;
-  case 9:
-    using ul = unsigned long;
-    callback(ul{});
-    break;
-  case 10:
-    callback(float{});
-    break;
-  case 11:
-    callback(double{});
-    break;
-  case 12:
-    using LD = long double;
-    callback(LD{});
-    break;
-  }
-}
-
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
-  if (Size <= 3) {
-    return 0;
-  }
-
-  // switch types depending on the first byte of the input
-  const auto first = Data[0] & 0x0F;
-  const auto second = (Data[0] & 0xF0) >> 4;
-  Data++;
-  Size--;
-
-  auto outer = [=](auto param1) {
-    auto inner = [=](auto param2) {
-      invoke_fmt<decltype(param1), decltype(param2)>(Data, Size);
-    };
-    invoke(second, inner);
-  };
-
-  try {
-    invoke(first, outer);
-  } catch (std::exception& /*e*/) {
-  }
-  return 0;
-}
diff --git a/test/gmock-gtest-all.cc b/test/gmock-gtest-all.cc
index 980cc60..bc43f93 100644
--- a/test/gmock-gtest-all.cc
+++ b/test/gmock-gtest-all.cc
@@ -344,6 +344,7 @@
 #  include <sys/mman.h>  // NOLINT
 #  include <sys/time.h>  // NOLINT
 #  include <unistd.h>    // NOLINT
+
 #  include <string>
 
 #elif GTEST_OS_SYMBIAN
@@ -7728,6 +7729,7 @@
 #  include <sys/syslimits.h>
 #else
 #  include <limits.h>
+
 #  include <climits>  // Some Linux distributions define PATH_MAX here.
 #endif                // GTEST_OS_WINDOWS_MOBILE
 
@@ -8899,6 +8901,7 @@
 
 #include <ctype.h>
 #include <stdio.h>
+
 #include <ostream>  // NOLINT
 #include <string>
 
@@ -9494,6 +9497,7 @@
 // This file implements cardinalities.
 
 #include <limits.h>
+
 #include <ostream>  // NOLINT
 #include <sstream>
 #include <string>
@@ -9646,6 +9650,7 @@
 // USE THEM IN USER CODE.
 
 #include <ctype.h>
+
 #include <ostream>  // NOLINT
 #include <string>
 
@@ -9808,6 +9813,7 @@
 // utilities for defining matchers.
 
 #include <string.h>
+
 #include <sstream>
 #include <string>
 
@@ -10291,6 +10297,7 @@
 // EXPECT_CALL).
 
 #include <stdlib.h>
+
 #include <iostream>  // NOLINT
 #include <map>
 #include <set>
diff --git a/test/grisu-test.cc b/test/grisu-test.cc
deleted file mode 100644
index 3fc670c..0000000
--- a/test/grisu-test.cc
+++ /dev/null
@@ -1,75 +0,0 @@
-// Formatting library for C++ - Grisu tests
-//
-// Copyright (c) 2012 - present, Victor Zverovich
-// All rights reserved.
-//
-// For the license information refer to format.h.
-
-#include "fmt/format.h"
-#include "gtest.h"
-
-static bool reported_skipped;
-
-#undef TEST
-#define TEST(test_fixture, test_name)        \
-  void test_fixture##test_name();            \
-  GTEST_TEST(test_fixture, test_name) {      \
-    if (FMT_USE_GRISU) {                     \
-      test_fixture##test_name();             \
-    } else if (!reported_skipped) {          \
-      reported_skipped = true;               \
-      fmt::print("Skipping Grisu tests.\n"); \
-    }                                        \
-  }                                          \
-  void test_fixture##test_name()
-
-TEST(GrisuTest, NaN) {
-  auto nan = std::numeric_limits<double>::quiet_NaN();
-  EXPECT_EQ("nan", fmt::format("{}", nan));
-  EXPECT_EQ("-nan", fmt::format("{}", -nan));
-}
-
-TEST(GrisuTest, Inf) {
-  auto inf = std::numeric_limits<double>::infinity();
-  EXPECT_EQ("inf", fmt::format("{}", inf));
-  EXPECT_EQ("-inf", fmt::format("{}", -inf));
-}
-
-TEST(GrisuTest, Zero) { EXPECT_EQ("0.0", fmt::format("{}", 0.0)); }
-
-TEST(GrisuTest, Round) {
-  EXPECT_EQ("1.9156918820264798e-56",
-            fmt::format("{}", 1.9156918820264798e-56));
-  EXPECT_EQ("0.0000", fmt::format("{:.4f}", 7.2809479766055470e-15));
-}
-
-TEST(GrisuTest, Prettify) {
-  EXPECT_EQ("0.0001", fmt::format("{}", 1e-4));
-  EXPECT_EQ("1e-05", fmt::format("{}", 1e-5));
-  EXPECT_EQ("9.999e-05", fmt::format("{}", 9.999e-5));
-  EXPECT_EQ("10000000000.0", fmt::format("{}", 1e10));
-  EXPECT_EQ("100000000000.0", fmt::format("{}", 1e11));
-  EXPECT_EQ("12340000000.0", fmt::format("{}", 1234e7));
-  EXPECT_EQ("12.34", fmt::format("{}", 1234e-2));
-  EXPECT_EQ("0.001234", fmt::format("{}", 1234e-6));
-  EXPECT_EQ("0.1", fmt::format("{}", 0.1f));
-  EXPECT_EQ("0.10000000149011612", fmt::format("{}", double(0.1f)));
-}
-
-TEST(GrisuTest, ZeroPrecision) { EXPECT_EQ("1", fmt::format("{:.0}", 1.0)); }
-
-TEST(GrisuTest, Fallback) {
-  EXPECT_EQ("1e+23", fmt::format("{}", 1e23));
-  EXPECT_EQ("9e-265", fmt::format("{}", 9e-265));
-  EXPECT_EQ("5.423717798060526e+125",
-            fmt::format("{}", 5.423717798060526e+125));
-  EXPECT_EQ("1.372371880954233e-288",
-            fmt::format("{}", 1.372371880954233e-288));
-  EXPECT_EQ("55388492.622190244", fmt::format("{}", 55388492.622190244));
-  EXPECT_EQ("2.2506787569811123e-253",
-            fmt::format("{}", 2.2506787569811123e-253));
-  EXPECT_EQ("1103618912042992.8", fmt::format("{}", 1103618912042992.8));
-  // pow(2, -25) - assymetric boundaries:
-  EXPECT_EQ("2.9802322387695312e-08",
-            fmt::format("{}", 2.9802322387695312e-08));
-}
diff --git a/test/gtest-extra-test.cc b/test/gtest-extra-test.cc
index 99d1d03..ea72860 100644
--- a/test/gtest-extra-test.cc
+++ b/test/gtest-extra-test.cc
@@ -8,6 +8,7 @@
 #include "gtest-extra.h"
 
 #include <gtest/gtest-spi.h>
+
 #include <algorithm>
 #include <cstring>
 #include <memory>
@@ -167,22 +168,24 @@
 // Tests that assertion arguments are evaluated exactly once.
 TEST_F(SingleEvaluationTest, WriteTests) {
   // successful EXPECT_WRITE
-  EXPECT_WRITE(stdout,
-               {  // NOLINT
-                 a_++;
-                 std::printf("test");
-               },
-               (b_++, "test"));
+  EXPECT_WRITE(
+      stdout,
+      {  // NOLINT
+        a_++;
+        std::printf("test");
+      },
+      (b_++, "test"));
   EXPECT_EQ(1, a_);
   EXPECT_EQ(1, b_);
 
   // failed EXPECT_WRITE
-  EXPECT_NONFATAL_FAILURE(EXPECT_WRITE(stdout,
-                                       {  // NOLINT
-                                         a_++;
-                                         std::printf("test");
-                                       },
-                                       (b_++, "other")),
+  EXPECT_NONFATAL_FAILURE(EXPECT_WRITE(
+                              stdout,
+                              {  // NOLINT
+                                a_++;
+                                std::printf("test");
+                              },
+                              (b_++, "other")),
                           "Actual: test");
   EXPECT_EQ(2, a_);
   EXPECT_EQ(2, b_);
@@ -417,16 +420,17 @@
   std::unique_ptr<OutputRedirect> redir(new OutputRedirect(f.get()));
   // Put a character in a file buffer.
   EXPECT_EQ('x', fputc('x', f.get()));
-  EXPECT_WRITE(stderr,
-               {
-                 // The close function must be called inside EXPECT_WRITE,
-                 // otherwise the system may recycle closed file descriptor when
-                 // redirecting the output in EXPECT_STDERR and the second close
-                 // will break output redirection.
-                 FMT_POSIX(close(write_fd));
-                 SUPPRESS_ASSERT(redir.reset(nullptr));
-               },
-               format_system_error(EBADF, "cannot flush stream"));
+  EXPECT_WRITE(
+      stderr,
+      {
+        // The close function must be called inside EXPECT_WRITE,
+        // otherwise the system may recycle closed file descriptor when
+        // redirecting the output in EXPECT_STDERR and the second close
+        // will break output redirection.
+        FMT_POSIX(close(write_fd));
+        SUPPRESS_ASSERT(redir.reset(nullptr));
+      },
+      format_system_error(EBADF, "cannot flush stream"));
   write_copy.dup2(write_fd);  // "undo" close or dtor of buffered_file will fail
 }
 
diff --git a/test/gtest-extra.cc b/test/gtest-extra.cc
index cf92852..58628a8 100644
--- a/test/gtest-extra.cc
+++ b/test/gtest-extra.cc
@@ -57,7 +57,7 @@
   if (read_end_.descriptor() == -1) return content;  // Already read.
   enum { BUFFER_SIZE = 4096 };
   char buffer[BUFFER_SIZE];
-  std::size_t count = 0;
+  size_t count = 0;
   do {
     count = read_end_.read(buffer, BUFFER_SIZE);
     content.append(buffer, count);
@@ -66,9 +66,9 @@
   return content;
 }
 
-std::string read(file& f, std::size_t count) {
+std::string read(file& f, size_t count) {
   std::string buffer(count, '\0');
-  std::size_t n = 0, offset = 0;
+  size_t n = 0, offset = 0;
   do {
     n = f.read(&buffer[offset], count - offset);
     // We can't read more than size_t bytes since count has type size_t.
diff --git a/test/gtest-extra.h b/test/gtest-extra.h
index ee33561..01c70dd 100644
--- a/test/gtest-extra.h
+++ b/test/gtest-extra.h
@@ -9,8 +9,9 @@
 #define FMT_GTEST_EXTRA_H_
 
 #include <string>
+
+#include "fmt/os.h"
 #include "gmock.h"
-#include "fmt/posix.h"
 
 #define FMT_TEST_THROW_(statement, expected_exception, expected_message, fail) \
   GTEST_AMBIGUOUS_ELSE_BLOCKER_                                                \
@@ -137,13 +138,20 @@
     EXPECT_SYSTEM_ERROR(SUPPRESS_ASSERT(statement), error_code, message)
 
 // Attempts to read count characters from a file.
-std::string read(fmt::file& f, std::size_t count);
+std::string read(fmt::file& f, size_t count);
 
 #  define EXPECT_READ(file, expected_content) \
-    EXPECT_EQ(expected_content, read(file, std::strlen(expected_content)))
+    EXPECT_EQ(expected_content, \
+              read(file, fmt::string_view(expected_content).size()))
 
 #else
-#  define EXPECT_WRITE(file, statement, expected_output) SUCCEED()
+#  define EXPECT_WRITE(file, statement, expected_output) \
+    do {                                                 \
+      (void)(file);                                      \
+      (void)(statement);                                 \
+      (void)(expected_output);                           \
+      SUCCEED();                                         \
+    } while (false)
 #endif  // FMT_USE_FCNTL
 
 template <typename Mock> struct ScopedMock : testing::StrictMock<Mock> {
diff --git a/test/locale-test.cc b/test/locale-test.cc
index a064ecd..c7c30f2 100644
--- a/test/locale-test.cc
+++ b/test/locale-test.cc
@@ -6,9 +6,12 @@
 // For the license information refer to format.h.
 
 #include "fmt/locale.h"
+
+#include <complex>
+
 #include "gmock.h"
 
-using fmt::internal::max_value;
+using fmt::detail::max_value;
 
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 template <typename Char> struct numpunct : std::numpunct<Char> {
@@ -41,49 +44,117 @@
 
 TEST(LocaleTest, DoubleDecimalPoint) {
   std::locale loc(std::locale(), new numpunct<char>());
-  EXPECT_EQ("1?23", fmt::format(loc, "{:n}", 1.23));
+  EXPECT_EQ("1?23", fmt::format(loc, "{:L}", 1.23));
 }
 
 TEST(LocaleTest, Format) {
   std::locale loc(std::locale(), new numpunct<char>());
-  EXPECT_EQ("1234567", fmt::format(std::locale(), "{:n}", 1234567));
-  EXPECT_EQ("1~234~567", fmt::format(loc, "{:n}", 1234567));
+  EXPECT_EQ("1234567", fmt::format(std::locale(), "{:L}", 1234567));
+  EXPECT_EQ("1~234~567", fmt::format(loc, "{:L}", 1234567));
+  EXPECT_EQ("-1~234~567", fmt::format(loc, "{:L}", -1234567));
+  EXPECT_EQ("-256", fmt::format(loc, "{:L}", -256));
   fmt::format_arg_store<fmt::format_context, int> as{1234567};
-  EXPECT_EQ("1~234~567", fmt::vformat(loc, "{:n}", fmt::format_args(as)));
+  EXPECT_EQ("1~234~567", fmt::vformat(loc, "{:L}", fmt::format_args(as)));
   std::string s;
-  fmt::format_to(std::back_inserter(s), loc, "{:n}", 1234567);
+  fmt::format_to(std::back_inserter(s), loc, "{:L}", 1234567);
   EXPECT_EQ("1~234~567", s);
 
   std::locale no_grouping_loc(std::locale(), new no_grouping<char>());
-  EXPECT_EQ("1234567", fmt::format(no_grouping_loc, "{:n}", 1234567));
+  EXPECT_EQ("1234567", fmt::format(no_grouping_loc, "{:L}", 1234567));
 
   std::locale special_grouping_loc(std::locale(), new special_grouping<char>());
-  EXPECT_EQ("1,23,45,678", fmt::format(special_grouping_loc, "{:n}", 12345678));
+  EXPECT_EQ("1,23,45,678", fmt::format(special_grouping_loc, "{:L}", 12345678));
+  EXPECT_EQ("12,345", fmt::format(special_grouping_loc, "{:L}", 12345));
 
   std::locale small_grouping_loc(std::locale(), new small_grouping<char>());
   EXPECT_EQ("4,2,9,4,9,6,7,2,9,5",
-            fmt::format(small_grouping_loc, "{:n}", max_value<uint32_t>()));
+            fmt::format(small_grouping_loc, "{:L}", max_value<uint32_t>()));
+}
+
+TEST(LocaleTest, FormatDetaultAlign) {
+  std::locale special_grouping_loc(std::locale(), new special_grouping<char>());
+  EXPECT_EQ("  12,345", fmt::format(special_grouping_loc, "{:8L}", 12345));
 }
 
 TEST(LocaleTest, WFormat) {
   std::locale loc(std::locale(), new numpunct<wchar_t>());
-  EXPECT_EQ(L"1234567", fmt::format(std::locale(), L"{:n}", 1234567));
-  EXPECT_EQ(L"1~234~567", fmt::format(loc, L"{:n}", 1234567));
+  EXPECT_EQ(L"1234567", fmt::format(std::locale(), L"{:L}", 1234567));
+  EXPECT_EQ(L"1~234~567", fmt::format(loc, L"{:L}", 1234567));
   fmt::format_arg_store<fmt::wformat_context, int> as{1234567};
-  EXPECT_EQ(L"1~234~567", fmt::vformat(loc, L"{:n}", fmt::wformat_args(as)));
-  EXPECT_EQ(L"1234567", fmt::format(std::locale("C"), L"{:n}", 1234567));
+  EXPECT_EQ(L"1~234~567", fmt::vformat(loc, L"{:L}", fmt::wformat_args(as)));
+  EXPECT_EQ(L"1234567", fmt::format(std::locale("C"), L"{:L}", 1234567));
 
   std::locale no_grouping_loc(std::locale(), new no_grouping<wchar_t>());
-  EXPECT_EQ(L"1234567", fmt::format(no_grouping_loc, L"{:n}", 1234567));
+  EXPECT_EQ(L"1234567", fmt::format(no_grouping_loc, L"{:L}", 1234567));
 
   std::locale special_grouping_loc(std::locale(),
                                    new special_grouping<wchar_t>());
   EXPECT_EQ(L"1,23,45,678",
-            fmt::format(special_grouping_loc, L"{:n}", 12345678));
+            fmt::format(special_grouping_loc, L"{:L}", 12345678));
 
   std::locale small_grouping_loc(std::locale(), new small_grouping<wchar_t>());
   EXPECT_EQ(L"4,2,9,4,9,6,7,2,9,5",
-            fmt::format(small_grouping_loc, L"{:n}", max_value<uint32_t>()));
+            fmt::format(small_grouping_loc, L"{:L}", max_value<uint32_t>()));
+}
+
+TEST(LocaleTest, DoubleFormatter) {
+  auto loc = std::locale(std::locale(), new special_grouping<char>());
+  auto f = fmt::formatter<int>();
+  auto parse_ctx = fmt::format_parse_context("L");
+  f.parse(parse_ctx);
+  char buf[10] = {};
+  fmt::basic_format_context<char*, char> format_ctx(
+      buf, {}, fmt::detail::locale_ref(loc));
+  *f.format(12345, format_ctx) = 0;
+  EXPECT_STREQ("12,345", buf);
+}
+
+FMT_BEGIN_NAMESPACE
+template <class charT> struct formatter<std::complex<double>, charT> {
+ private:
+  detail::dynamic_format_specs<char> specs_;
+
+ public:
+  typename basic_format_parse_context<charT>::iterator parse(
+      basic_format_parse_context<charT>& ctx) {
+    using handler_type =
+        detail::dynamic_specs_handler<basic_format_parse_context<charT>>;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                detail::type::string_type);
+    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
+    detail::parse_float_type_spec(specs_, ctx.error_handler());
+    return it;
+  }
+
+  template <class FormatContext>
+  typename FormatContext::iterator format(const std::complex<double>& c,
+                                          FormatContext& ctx) {
+    detail::handle_dynamic_spec<detail::precision_checker>(
+        specs_.precision, specs_.precision_ref, ctx);
+    auto format_specs = std::string();
+    if (specs_.precision > 0)
+      format_specs = fmt::format(".{}", specs_.precision);
+    if (specs_.type)
+      format_specs += specs_.type;
+    auto real = fmt::format(ctx.locale().template get<std::locale>(),
+                            "{:" + format_specs + "}", c.real());
+    auto imag = fmt::format(ctx.locale().template get<std::locale>(),
+                            "{:" + format_specs + "}", c.imag());
+    auto fill_align_width = std::string();
+    if (specs_.width > 0)
+      fill_align_width = fmt::format(">{}", specs_.width);
+    return format_to(
+        ctx.out(), "{:" + fill_align_width + "}",
+        fmt::format(c.real() != 0 ? "({0}+{1}i)" : "{1}i", real, imag));
+  }
+};
+FMT_END_NAMESPACE
+
+TEST(FormatTest, Complex) {
+  std::string s = fmt::format("{}", std::complex<double>(1, 2));
+  EXPECT_EQ(s, "(1+2i)");
+  EXPECT_EQ(fmt::format("{:.2f}", std::complex<double>(1, 2)), "(1.00+2.00i)");
+  EXPECT_EQ(fmt::format("{:8}", std::complex<double>(1, 2)), "  (1+2i)");
 }
 
 #endif  // FMT_STATIC_THOUSANDS_SEPARATOR
diff --git a/test/mock-allocator.h b/test/mock-allocator.h
index 1dd2dad..513a62e 100644
--- a/test/mock-allocator.h
+++ b/test/mock-allocator.h
@@ -16,8 +16,8 @@
   mock_allocator() {}
   mock_allocator(const mock_allocator&) {}
   typedef T value_type;
-  MOCK_METHOD1_T(allocate, T*(std::size_t n));
-  MOCK_METHOD2_T(deallocate, void(T* p, std::size_t n));
+  MOCK_METHOD1_T(allocate, T*(size_t n));
+  MOCK_METHOD2_T(deallocate, void(T* p, size_t n));
 };
 
 template <typename Allocator> class allocator_ref {
@@ -51,10 +51,10 @@
  public:
   Allocator* get() const { return alloc_; }
 
-  value_type* allocate(std::size_t n) {
+  value_type* allocate(size_t n) {
     return std::allocator_traits<Allocator>::allocate(*alloc_, n);
   }
-  void deallocate(value_type* p, std::size_t n) { alloc_->deallocate(p, n); }
+  void deallocate(value_type* p, size_t n) { alloc_->deallocate(p, n); }
 };
 
 #endif  // FMT_MOCK_ALLOCATOR_H_
diff --git a/test/os-test.cc b/test/os-test.cc
new file mode 100644
index 0000000..359b5ff
--- /dev/null
+++ b/test/os-test.cc
@@ -0,0 +1,532 @@
+// Formatting library for C++ - tests of the OS-specific functionality
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#include "fmt/os.h"
+
+#include <cstdlib>  // std::exit
+#include <cstring>
+#include <memory>
+
+#include "gtest-extra.h"
+#include "util.h"
+
+#ifdef fileno
+#  undef fileno
+#endif
+
+using fmt::buffered_file;
+using fmt::error_code;
+
+#ifdef _WIN32
+
+#  include <windows.h>
+
+TEST(UtilTest, UTF16ToUTF8) {
+  std::string s = "ёжик";
+  fmt::detail::utf16_to_utf8 u(L"\x0451\x0436\x0438\x043A");
+  EXPECT_EQ(s, u.str());
+  EXPECT_EQ(s.size(), u.size());
+}
+
+TEST(UtilTest, UTF16ToUTF8EmptyString) {
+  std::string s = "";
+  fmt::detail::utf16_to_utf8 u(L"");
+  EXPECT_EQ(s, u.str());
+  EXPECT_EQ(s.size(), u.size());
+}
+
+template <typename Converter, typename Char>
+void check_utf_conversion_error(
+    const char* message,
+    fmt::basic_string_view<Char> str = fmt::basic_string_view<Char>(0, 1)) {
+  fmt::memory_buffer out;
+  fmt::detail::format_windows_error(out, ERROR_INVALID_PARAMETER, message);
+  fmt::system_error error(0, "");
+  try {
+    (Converter)(str);
+  } catch (const fmt::system_error& e) {
+    error = e;
+  }
+  EXPECT_EQ(ERROR_INVALID_PARAMETER, error.error_code());
+  EXPECT_EQ(fmt::to_string(out), error.what());
+}
+
+TEST(UtilTest, UTF16ToUTF8Error) {
+  check_utf_conversion_error<fmt::detail::utf16_to_utf8, wchar_t>(
+      "cannot convert string from UTF-16 to UTF-8");
+}
+
+TEST(UtilTest, UTF16ToUTF8Convert) {
+  fmt::detail::utf16_to_utf8 u;
+  EXPECT_EQ(ERROR_INVALID_PARAMETER, u.convert(fmt::wstring_view(0, 1)));
+  EXPECT_EQ(ERROR_INVALID_PARAMETER,
+            u.convert(fmt::wstring_view(L"foo", INT_MAX + 1u)));
+}
+
+TEST(UtilTest, FormatWindowsError) {
+  LPWSTR message = 0;
+  FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+                     FORMAT_MESSAGE_IGNORE_INSERTS,
+                 0, ERROR_FILE_EXISTS,
+                 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                 reinterpret_cast<LPWSTR>(&message), 0, 0);
+  fmt::detail::utf16_to_utf8 utf8_message(message);
+  LocalFree(message);
+  fmt::memory_buffer actual_message;
+  fmt::detail::format_windows_error(actual_message, ERROR_FILE_EXISTS, "test");
+  EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
+            fmt::to_string(actual_message));
+  actual_message.resize(0);
+  auto max_size = fmt::detail::max_value<size_t>() / 2;
+  fmt::detail::format_windows_error(actual_message, ERROR_FILE_EXISTS,
+                                    fmt::string_view(nullptr, max_size));
+  EXPECT_EQ(fmt::format("error {}", ERROR_FILE_EXISTS),
+            fmt::to_string(actual_message));
+}
+
+TEST(UtilTest, FormatLongWindowsError) {
+  LPWSTR message = 0;
+  // this error code is not available on all Windows platforms and
+  // Windows SDKs, so do not fail the test if the error string cannot
+  // be retrieved.
+  const int provisioning_not_allowed =
+      0x80284013L /*TBS_E_PROVISIONING_NOT_ALLOWED*/;
+  if (FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                         FORMAT_MESSAGE_FROM_SYSTEM |
+                         FORMAT_MESSAGE_IGNORE_INSERTS,
+                     0, static_cast<DWORD>(provisioning_not_allowed),
+                     MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                     reinterpret_cast<LPWSTR>(&message), 0, 0) == 0) {
+    return;
+  }
+  fmt::detail::utf16_to_utf8 utf8_message(message);
+  LocalFree(message);
+  fmt::memory_buffer actual_message;
+  fmt::detail::format_windows_error(actual_message, provisioning_not_allowed,
+                                    "test");
+  EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
+            fmt::to_string(actual_message));
+}
+
+TEST(UtilTest, WindowsError) {
+  fmt::system_error error(0, "");
+  try {
+    throw fmt::windows_error(ERROR_FILE_EXISTS, "test {}", "error");
+  } catch (const fmt::system_error& e) {
+    error = e;
+  }
+  fmt::memory_buffer message;
+  fmt::detail::format_windows_error(message, ERROR_FILE_EXISTS, "test error");
+  EXPECT_EQ(to_string(message), error.what());
+  EXPECT_EQ(ERROR_FILE_EXISTS, error.error_code());
+}
+
+TEST(UtilTest, ReportWindowsError) {
+  fmt::memory_buffer out;
+  fmt::detail::format_windows_error(out, ERROR_FILE_EXISTS, "test error");
+  out.push_back('\n');
+  EXPECT_WRITE(stderr,
+               fmt::report_windows_error(ERROR_FILE_EXISTS, "test error"),
+               fmt::to_string(out));
+}
+
+#endif  // _WIN32
+
+#if FMT_USE_FCNTL
+
+using fmt::file;
+
+// Checks if the file is open by reading one character from it.
+static bool isopen(int fd) {
+  char buffer;
+  return FMT_POSIX(read(fd, &buffer, 1)) == 1;
+}
+
+static bool isclosed(int fd) {
+  char buffer;
+  std::streamsize result = 0;
+  SUPPRESS_ASSERT(result = FMT_POSIX(read(fd, &buffer, 1)));
+  return result == -1 && errno == EBADF;
+}
+
+// Opens a file for reading.
+static file open_file() {
+  file read_end, write_end;
+  file::pipe(read_end, write_end);
+  write_end.write(FILE_CONTENT, std::strlen(FILE_CONTENT));
+  write_end.close();
+  return read_end;
+}
+
+// Attempts to write a string to a file.
+static void write(file& f, fmt::string_view s) {
+  size_t num_chars_left = s.size();
+  const char* ptr = s.data();
+  do {
+    size_t count = f.write(ptr, num_chars_left);
+    ptr += count;
+    // We can't write more than size_t bytes since num_chars_left
+    // has type size_t.
+    num_chars_left -= count;
+  } while (num_chars_left != 0);
+}
+
+TEST(BufferedFileTest, DefaultCtor) {
+  buffered_file f;
+  EXPECT_TRUE(f.get() == nullptr);
+}
+
+TEST(BufferedFileTest, MoveCtor) {
+  buffered_file bf = open_buffered_file();
+  FILE* fp = bf.get();
+  EXPECT_TRUE(fp != nullptr);
+  buffered_file bf2(std::move(bf));
+  EXPECT_EQ(fp, bf2.get());
+  EXPECT_TRUE(bf.get() == nullptr);
+}
+
+TEST(BufferedFileTest, MoveAssignment) {
+  buffered_file bf = open_buffered_file();
+  FILE* fp = bf.get();
+  EXPECT_TRUE(fp != nullptr);
+  buffered_file bf2;
+  bf2 = std::move(bf);
+  EXPECT_EQ(fp, bf2.get());
+  EXPECT_TRUE(bf.get() == nullptr);
+}
+
+TEST(BufferedFileTest, MoveAssignmentClosesFile) {
+  buffered_file bf = open_buffered_file();
+  buffered_file bf2 = open_buffered_file();
+  int old_fd = bf2.fileno();
+  bf2 = std::move(bf);
+  EXPECT_TRUE(isclosed(old_fd));
+}
+
+TEST(BufferedFileTest, MoveFromTemporaryInCtor) {
+  FILE* fp = nullptr;
+  buffered_file f(open_buffered_file(&fp));
+  EXPECT_EQ(fp, f.get());
+}
+
+TEST(BufferedFileTest, MoveFromTemporaryInAssignment) {
+  FILE* fp = nullptr;
+  buffered_file f;
+  f = open_buffered_file(&fp);
+  EXPECT_EQ(fp, f.get());
+}
+
+TEST(BufferedFileTest, MoveFromTemporaryInAssignmentClosesFile) {
+  buffered_file f = open_buffered_file();
+  int old_fd = f.fileno();
+  f = open_buffered_file();
+  EXPECT_TRUE(isclosed(old_fd));
+}
+
+TEST(BufferedFileTest, CloseFileInDtor) {
+  int fd = 0;
+  {
+    buffered_file f = open_buffered_file();
+    fd = f.fileno();
+  }
+  EXPECT_TRUE(isclosed(fd));
+}
+
+TEST(BufferedFileTest, CloseErrorInDtor) {
+  std::unique_ptr<buffered_file> f(new buffered_file(open_buffered_file()));
+  EXPECT_WRITE(
+      stderr,
+      {
+        // The close function must be called inside EXPECT_WRITE,
+        // otherwise the system may recycle closed file descriptor when
+        // redirecting the output in EXPECT_STDERR and the second close
+        // will break output redirection.
+        FMT_POSIX(close(f->fileno()));
+        SUPPRESS_ASSERT(f.reset(nullptr));
+      },
+      format_system_error(EBADF, "cannot close file") + "\n");
+}
+
+TEST(BufferedFileTest, Close) {
+  buffered_file f = open_buffered_file();
+  int fd = f.fileno();
+  f.close();
+  EXPECT_TRUE(f.get() == nullptr);
+  EXPECT_TRUE(isclosed(fd));
+}
+
+TEST(BufferedFileTest, CloseError) {
+  buffered_file f = open_buffered_file();
+  FMT_POSIX(close(f.fileno()));
+  EXPECT_SYSTEM_ERROR_NOASSERT(f.close(), EBADF, "cannot close file");
+  EXPECT_TRUE(f.get() == nullptr);
+}
+
+TEST(BufferedFileTest, Fileno) {
+  buffered_file f;
+#  ifndef __COVERITY__
+  // fileno on a null FILE pointer either crashes or returns an error.
+  // Disable Coverity because this is intentional.
+  EXPECT_DEATH_IF_SUPPORTED(
+      {
+        try {
+          f.fileno();
+        } catch (const fmt::system_error&) {
+          std::exit(1);
+        }
+      },
+      "");
+#  endif
+  f = open_buffered_file();
+  EXPECT_TRUE(f.fileno() != -1);
+  file copy = file::dup(f.fileno());
+  EXPECT_READ(copy, FILE_CONTENT);
+}
+
+TEST(OStreamTest, Move) {
+  fmt::ostream out = fmt::output_file("test-file");
+  fmt::ostream moved(std::move(out));
+  moved.print("hello");
+}
+
+TEST(OStreamTest, Print) {
+  fmt::ostream out = fmt::output_file("test-file");
+  out.print("The answer is {}.\n", 42);
+  out.close();
+  file in("test-file", file::RDONLY);
+  EXPECT_READ(in, "The answer is 42.\n");
+}
+
+TEST(OStreamTest, BufferBoundary) {
+  auto str = std::string(4096, 'x');
+  fmt::ostream out = fmt::output_file("test-file");
+  out.print("{}", str);
+  out.print("{}", str);
+  out.close();
+  file in("test-file", file::RDONLY);
+  EXPECT_READ(in, str + str);
+}
+
+TEST(OStreamTest, BufferSize) {
+  fmt::ostream out = fmt::output_file("test-file", fmt::buffer_size=1);
+  out.print("{}", "foo");
+  out.close();
+  file in("test-file", file::RDONLY);
+  EXPECT_READ(in, "foo");
+}
+
+TEST(FileTest, DefaultCtor) {
+  file f;
+  EXPECT_EQ(-1, f.descriptor());
+}
+
+TEST(FileTest, OpenBufferedFileInCtor) {
+  FILE* fp = safe_fopen("test-file", "w");
+  std::fputs(FILE_CONTENT, fp);
+  std::fclose(fp);
+  file f("test-file", file::RDONLY);
+  ASSERT_TRUE(isopen(f.descriptor()));
+}
+
+TEST(FileTest, OpenBufferedFileError) {
+  EXPECT_SYSTEM_ERROR(file("nonexistent", file::RDONLY), ENOENT,
+                      "cannot open file nonexistent");
+}
+
+TEST(FileTest, MoveCtor) {
+  file f = open_file();
+  int fd = f.descriptor();
+  EXPECT_NE(-1, fd);
+  file f2(std::move(f));
+  EXPECT_EQ(fd, f2.descriptor());
+  EXPECT_EQ(-1, f.descriptor());
+}
+
+TEST(FileTest, MoveAssignment) {
+  file f = open_file();
+  int fd = f.descriptor();
+  EXPECT_NE(-1, fd);
+  file f2;
+  f2 = std::move(f);
+  EXPECT_EQ(fd, f2.descriptor());
+  EXPECT_EQ(-1, f.descriptor());
+}
+
+TEST(FileTest, MoveAssignmentClosesFile) {
+  file f = open_file();
+  file f2 = open_file();
+  int old_fd = f2.descriptor();
+  f2 = std::move(f);
+  EXPECT_TRUE(isclosed(old_fd));
+}
+
+static file OpenBufferedFile(int& fd) {
+  file f = open_file();
+  fd = f.descriptor();
+  return f;
+}
+
+TEST(FileTest, MoveFromTemporaryInCtor) {
+  int fd = 0xdead;
+  file f(OpenBufferedFile(fd));
+  EXPECT_EQ(fd, f.descriptor());
+}
+
+TEST(FileTest, MoveFromTemporaryInAssignment) {
+  int fd = 0xdead;
+  file f;
+  f = OpenBufferedFile(fd);
+  EXPECT_EQ(fd, f.descriptor());
+}
+
+TEST(FileTest, MoveFromTemporaryInAssignmentClosesFile) {
+  int fd = 0xdead;
+  file f = open_file();
+  int old_fd = f.descriptor();
+  f = OpenBufferedFile(fd);
+  EXPECT_TRUE(isclosed(old_fd));
+}
+
+TEST(FileTest, CloseFileInDtor) {
+  int fd = 0;
+  {
+    file f = open_file();
+    fd = f.descriptor();
+  }
+  EXPECT_TRUE(isclosed(fd));
+}
+
+TEST(FileTest, CloseErrorInDtor) {
+  std::unique_ptr<file> f(new file(open_file()));
+  EXPECT_WRITE(
+      stderr,
+      {
+        // The close function must be called inside EXPECT_WRITE,
+        // otherwise the system may recycle closed file descriptor when
+        // redirecting the output in EXPECT_STDERR and the second close
+        // will break output redirection.
+        FMT_POSIX(close(f->descriptor()));
+        SUPPRESS_ASSERT(f.reset(nullptr));
+      },
+      format_system_error(EBADF, "cannot close file") + "\n");
+}
+
+TEST(FileTest, Close) {
+  file f = open_file();
+  int fd = f.descriptor();
+  f.close();
+  EXPECT_EQ(-1, f.descriptor());
+  EXPECT_TRUE(isclosed(fd));
+}
+
+TEST(FileTest, CloseError) {
+  file f = open_file();
+  FMT_POSIX(close(f.descriptor()));
+  EXPECT_SYSTEM_ERROR_NOASSERT(f.close(), EBADF, "cannot close file");
+  EXPECT_EQ(-1, f.descriptor());
+}
+
+TEST(FileTest, Read) {
+  file f = open_file();
+  EXPECT_READ(f, FILE_CONTENT);
+}
+
+TEST(FileTest, ReadError) {
+  file f("test-file", file::WRONLY);
+  char buf;
+  // We intentionally read from a file opened in the write-only mode to
+  // cause error.
+  EXPECT_SYSTEM_ERROR(f.read(&buf, 1), EBADF, "cannot read from file");
+}
+
+TEST(FileTest, Write) {
+  file read_end, write_end;
+  file::pipe(read_end, write_end);
+  write(write_end, "test");
+  write_end.close();
+  EXPECT_READ(read_end, "test");
+}
+
+TEST(FileTest, WriteError) {
+  file f("test-file", file::RDONLY);
+  // We intentionally write to a file opened in the read-only mode to
+  // cause error.
+  EXPECT_SYSTEM_ERROR(f.write(" ", 1), EBADF, "cannot write to file");
+}
+
+TEST(FileTest, Dup) {
+  file f = open_file();
+  file copy = file::dup(f.descriptor());
+  EXPECT_NE(f.descriptor(), copy.descriptor());
+  EXPECT_EQ(FILE_CONTENT, read(copy, std::strlen(FILE_CONTENT)));
+}
+
+#  ifndef __COVERITY__
+TEST(FileTest, DupError) {
+  int value = -1;
+  EXPECT_SYSTEM_ERROR_NOASSERT(file::dup(value), EBADF,
+                               "cannot duplicate file descriptor -1");
+}
+#  endif
+
+TEST(FileTest, Dup2) {
+  file f = open_file();
+  file copy = open_file();
+  f.dup2(copy.descriptor());
+  EXPECT_NE(f.descriptor(), copy.descriptor());
+  EXPECT_READ(copy, FILE_CONTENT);
+}
+
+TEST(FileTest, Dup2Error) {
+  file f = open_file();
+  EXPECT_SYSTEM_ERROR_NOASSERT(
+      f.dup2(-1), EBADF,
+      fmt::format("cannot duplicate file descriptor {} to -1", f.descriptor()));
+}
+
+TEST(FileTest, Dup2NoExcept) {
+  file f = open_file();
+  file copy = open_file();
+  error_code ec;
+  f.dup2(copy.descriptor(), ec);
+  EXPECT_EQ(ec.get(), 0);
+  EXPECT_NE(f.descriptor(), copy.descriptor());
+  EXPECT_READ(copy, FILE_CONTENT);
+}
+
+TEST(FileTest, Dup2NoExceptError) {
+  file f = open_file();
+  error_code ec;
+  SUPPRESS_ASSERT(f.dup2(-1, ec));
+  EXPECT_EQ(EBADF, ec.get());
+}
+
+TEST(FileTest, Pipe) {
+  file read_end, write_end;
+  file::pipe(read_end, write_end);
+  EXPECT_NE(-1, read_end.descriptor());
+  EXPECT_NE(-1, write_end.descriptor());
+  write(write_end, "test");
+  EXPECT_READ(read_end, "test");
+}
+
+TEST(FileTest, Fdopen) {
+  file read_end, write_end;
+  file::pipe(read_end, write_end);
+  int read_fd = read_end.descriptor();
+  EXPECT_EQ(read_fd, FMT_POSIX(fileno(read_end.fdopen("r").get())));
+}
+
+#  ifdef FMT_LOCALE
+TEST(LocaleTest, Strtod) {
+  fmt::locale loc;
+  const char *start = "4.2", *ptr = start;
+  EXPECT_EQ(4.2, loc.strtod(ptr));
+  EXPECT_EQ(start + 3, ptr);
+}
+#  endif
+#endif  // FMT_USE_FCNTL
diff --git a/test/ostream-test.cc b/test/ostream-test.cc
index 8a55d89..4f432fb 100644
--- a/test/ostream-test.cc
+++ b/test/ostream-test.cc
@@ -5,7 +5,6 @@
 //
 // For the license information refer to format.h.
 
-#define FMT_STRING_ALIAS 1
 #include "fmt/format.h"
 
 struct test {};
@@ -21,9 +20,10 @@
 };
 }  // namespace fmt
 
-#include "fmt/ostream.h"
-
 #include <sstream>
+
+#include "fmt/ostream.h"
+#include "fmt/ranges.h"
 #include "gmock.h"
 #include "gtest-extra.h"
 #include "util.h"
@@ -64,22 +64,23 @@
   EXPECT_EQ(L"0", fmt::format(L"{}", unstreamable_enum()));
 }
 
-using range = fmt::buffer_range<char>;
-
-struct test_arg_formatter : fmt::arg_formatter<range> {
+struct test_arg_formatter
+    : fmt::detail::arg_formatter<fmt::format_context::iterator, char> {
   fmt::format_parse_context parse_ctx;
   test_arg_formatter(fmt::format_context& ctx, fmt::format_specs& s)
-      : fmt::arg_formatter<range>(ctx, &parse_ctx, &s), parse_ctx("") {}
+      : fmt::detail::arg_formatter<fmt::format_context::iterator, char>(
+            ctx, &parse_ctx, &s),
+        parse_ctx("") {}
 };
 
 TEST(OStreamTest, CustomArg) {
   fmt::memory_buffer buffer;
-  fmt::internal::buffer<char>& base = buffer;
-  fmt::format_context ctx(std::back_inserter(base), fmt::format_args());
+  fmt::format_context ctx(fmt::detail::buffer_appender<char>{buffer},
+                          fmt::format_args());
   fmt::format_specs spec;
   test_arg_formatter af(ctx, spec);
   fmt::visit_format_arg(
-      af, fmt::internal::make_arg<fmt::format_context>(streamable_enum()));
+      af, fmt::detail::make_arg<fmt::format_context>(streamable_enum()));
   EXPECT_EQ("streamable_enum", std::string(buffer.data(), buffer.size()));
 }
 
@@ -95,7 +96,7 @@
 TEST(OStreamTest, FormatSpecs) {
   EXPECT_EQ("def  ", format("{0:<5}", TestString("def")));
   EXPECT_EQ("  def", format("{0:>5}", TestString("def")));
-#if FMT_NUMERIC_ALIGN
+#if FMT_DEPRECATED_NUMERIC_ALIGN
   EXPECT_THROW_MSG(format("{0:=5}", TestString("def")), format_error,
                    "format specifier requires numeric argument");
 #endif
@@ -140,18 +141,19 @@
   fmt::memory_buffer buffer;
   const char* foo = "foo";
   buffer.append(foo, foo + std::strlen(foo));
-  fmt::internal::write(os, buffer);
+  fmt::detail::write_buffer(os, buffer);
   EXPECT_EQ("foo", os.str());
 }
 
 TEST(OStreamTest, WriteToOStreamMaxSize) {
-  std::size_t max_size = fmt::internal::max_value<std::size_t>();
-  std::streamsize max_streamsize = fmt::internal::max_value<std::streamsize>();
-  if (max_size <= fmt::internal::to_unsigned(max_streamsize)) return;
+  size_t max_size = fmt::detail::max_value<size_t>();
+  std::streamsize max_streamsize = fmt::detail::max_value<std::streamsize>();
+  if (max_size <= fmt::detail::to_unsigned(max_streamsize)) return;
 
-  struct test_buffer : fmt::internal::buffer<char> {
-    explicit test_buffer(std::size_t size) { resize(size); }
-    void grow(std::size_t) {}
+  struct test_buffer final : fmt::detail::buffer<char> {
+    explicit test_buffer(size_t size)
+      : fmt::detail::buffer<char>(nullptr, size, size) {}
+    void grow(size_t) {}
   } buffer(max_size);
 
   struct mock_streambuf : std::streambuf {
@@ -171,13 +173,13 @@
   typedef std::make_unsigned<std::streamsize>::type ustreamsize;
   ustreamsize size = max_size;
   do {
-    auto n = std::min(size, fmt::internal::to_unsigned(max_streamsize));
+    auto n = std::min(size, fmt::detail::to_unsigned(max_streamsize));
     EXPECT_CALL(streambuf, xsputn(data, static_cast<std::streamsize>(n)))
         .WillOnce(testing::Return(max_streamsize));
     data += n;
     size -= n;
   } while (size != 0);
-  fmt::internal::write(os, buffer);
+  fmt::detail::write_buffer(os, buffer);
 }
 
 TEST(OStreamTest, Join) {
@@ -258,21 +260,71 @@
 struct explicitly_convertible_to_string_like {
   template <typename String,
             typename = typename std::enable_if<std::is_constructible<
-                String, const char*, std::size_t>::value>::type>
+                String, const char*, size_t>::value>::type>
   explicit operator String() const {
     return String("foo", 3u);
   }
 };
 
-TEST(FormatterTest, FormatExplicitlyConvertibleToStringLike) {
-  EXPECT_EQ("foo", fmt::format("{}", explicitly_convertible_to_string_like()));
-}
-
 std::ostream& operator<<(std::ostream& os,
                          explicitly_convertible_to_string_like) {
   return os << "bar";
 }
 
-TEST(FormatterTest, FormatExplicitlyConvertibleToStringLikeIgnoreInserter) {
-  EXPECT_EQ("foo", fmt::format("{}", explicitly_convertible_to_string_like()));
+TEST(OStreamTest, FormatExplicitlyConvertibleToStringLike) {
+  EXPECT_EQ("bar", fmt::format("{}", explicitly_convertible_to_string_like()));
 }
+
+#ifdef FMT_USE_STRING_VIEW
+struct explicitly_convertible_to_std_string_view {
+  explicit operator fmt::detail::std_string_view<char>() const {
+    return {"foo", 3u};
+  }
+};
+
+std::ostream& operator<<(std::ostream& os,
+                         explicitly_convertible_to_std_string_view) {
+  return os << "bar";
+}
+
+TEST(OStreamTest, FormatExplicitlyConvertibleToStdStringView) {
+  EXPECT_EQ("bar", fmt::format("{}", explicitly_convertible_to_string_like()));
+}
+#endif  // FMT_USE_STRING_VIEW
+
+struct streamable_and_convertible_to_bool {
+  operator bool() const { return true; }
+};
+
+std::ostream& operator<<(std::ostream& os, streamable_and_convertible_to_bool) {
+  return os << "foo";
+}
+
+TEST(OStreamTest, FormatConvertibleToBool) {
+  EXPECT_EQ("foo", fmt::format("{}", streamable_and_convertible_to_bool()));
+}
+
+struct copyfmt_test {};
+
+std::ostream& operator<<(std::ostream& os, copyfmt_test) {
+  std::ios ios(nullptr);
+  ios.copyfmt(os);
+  return os << "foo";
+}
+
+TEST(OStreamTest, CopyFmt) {
+  EXPECT_EQ("foo", fmt::format("{}", copyfmt_test()));
+}
+
+TEST(OStreamTest, CompileTimeString) {
+  EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), 42));
+}
+
+TEST(OStreamTest, ToString) {
+  EXPECT_EQ("ABC", fmt::to_string(fmt_test::ABC()));
+}
+
+TEST(OStreamTest, Range) {
+  auto strs = std::vector<TestString>{TestString("foo"), TestString("bar")};
+  EXPECT_EQ("{foo, bar}", format("{}", strs));
+}
\ No newline at end of file
diff --git a/test/posix-mock-test.cc b/test/posix-mock-test.cc
index fbd4a68..eb85756 100644
--- a/test/posix-mock-test.cc
+++ b/test/posix-mock-test.cc
@@ -11,13 +11,15 @@
 #endif
 
 #include "posix-mock.h"
-#include "../src/posix.cc"
 
 #include <errno.h>
 #include <fcntl.h>
+
 #include <climits>
 #include <memory>
 
+#include "../src/os.cc"
+
 #ifdef _WIN32
 #  include <io.h>
 #  undef max
@@ -47,11 +49,11 @@
 int fopen_count;
 int fclose_count;
 int fileno_count;
-std::size_t read_nbyte;
-std::size_t write_nbyte;
+size_t read_nbyte;
+size_t write_nbyte;
 bool sysconf_error;
 
-enum FStatSimulation { NONE, MAX_SIZE, ERROR } fstat_sim;
+enum { NONE, MAX_SIZE, ERROR } fstat_sim;
 }  // namespace
 
 #define EMULATE_EINTR(func, error_result) \
@@ -201,28 +203,28 @@
 using fmt::file;
 
 TEST(UtilTest, GetPageSize) {
-#ifdef _WIN32
+#  ifdef _WIN32
   SYSTEM_INFO si = {};
   GetSystemInfo(&si);
   EXPECT_EQ(si.dwPageSize, fmt::getpagesize());
-#else
+#  else
   EXPECT_EQ(sysconf(_SC_PAGESIZE), fmt::getpagesize());
   sysconf_error = true;
   EXPECT_SYSTEM_ERROR(fmt::getpagesize(), EINVAL,
                       "cannot get memory page size");
   sysconf_error = false;
-#endif
+#  endif
 }
 
 TEST(FileTest, OpenRetry) {
-  write_file("test", "there must be something here");
+  write_file("temp", "there must be something here");
   std::unique_ptr<file> f{nullptr};
-  EXPECT_RETRY(f.reset(new file("test", file::RDONLY)), open,
-               "cannot open file test");
-#ifndef _WIN32
+  EXPECT_RETRY(f.reset(new file("temp", file::RDONLY)), open,
+               "cannot open file temp");
+#  ifndef _WIN32
   char c = 0;
   f->read(&c, 1);
-#endif
+#  endif
 }
 
 TEST(FileTest, CloseNoRetryInDtor) {
@@ -230,14 +232,15 @@
   file::pipe(read_end, write_end);
   std::unique_ptr<file> f(new file(std::move(read_end)));
   int saved_close_count = 0;
-  EXPECT_WRITE(stderr,
-               {
-                 close_count = 1;
-                 f.reset(nullptr);
-                 saved_close_count = close_count;
-                 close_count = 0;
-               },
-               format_system_error(EINTR, "cannot close file") + "\n");
+  EXPECT_WRITE(
+      stderr,
+      {
+        close_count = 1;
+        f.reset(nullptr);
+        saved_close_count = close_count;
+        close_count = 0;
+      },
+      format_system_error(EINTR, "cannot close file") + "\n");
   EXPECT_EQ(2, saved_close_count);
 }
 
@@ -252,26 +255,26 @@
 
 TEST(FileTest, Size) {
   std::string content = "top secret, destroy before reading";
-  write_file("test", content);
-  file f("test", file::RDONLY);
+  write_file("temp", content);
+  file f("temp", file::RDONLY);
   EXPECT_GE(f.size(), 0);
   EXPECT_EQ(content.size(), static_cast<unsigned long long>(f.size()));
-#ifdef _WIN32
+#  ifdef _WIN32
   fmt::memory_buffer message;
-  fmt::internal::format_windows_error(message, ERROR_ACCESS_DENIED,
-                                      "cannot get file size");
+  fmt::detail::format_windows_error(message, ERROR_ACCESS_DENIED,
+                                    "cannot get file size");
   fstat_sim = ERROR;
   EXPECT_THROW_MSG(f.size(), fmt::windows_error, fmt::to_string(message));
   fstat_sim = NONE;
-#else
+#  else
   f.close();
   EXPECT_SYSTEM_ERROR(f.size(), EBADF, "cannot get file attributes");
-#endif
+#  endif
 }
 
 TEST(FileTest, MaxSize) {
-  write_file("test", "");
-  file f("test", file::RDONLY);
+  write_file("temp", "");
+  file f("temp", file::RDONLY);
   fstat_sim = MAX_SIZE;
   EXPECT_GE(f.size(), 0);
   EXPECT_EQ(max_file_size(), f.size());
@@ -285,7 +288,7 @@
   write_end.write("test", SIZE);
   write_end.close();
   char buffer[SIZE];
-  std::size_t count = 0;
+  size_t count = 0;
   EXPECT_RETRY(count = read_end.read(buffer, SIZE), read,
                "cannot read from file");
   EXPECT_EQ_POSIX(static_cast<std::streamsize>(SIZE), count);
@@ -295,26 +298,26 @@
   file read_end, write_end;
   file::pipe(read_end, write_end);
   enum { SIZE = 4 };
-  std::size_t count = 0;
+  size_t count = 0;
   EXPECT_RETRY(count = write_end.write("test", SIZE), write,
                "cannot write to file");
   write_end.close();
-#ifndef _WIN32
+#  ifndef _WIN32
   EXPECT_EQ(static_cast<std::streamsize>(SIZE), count);
   char buffer[SIZE + 1];
   read_end.read(buffer, SIZE);
   buffer[SIZE] = '\0';
   EXPECT_STREQ("test", buffer);
-#endif
+#  endif
 }
 
-#ifdef _WIN32
+#  ifdef _WIN32
 TEST(FileTest, ConvertReadCount) {
   file read_end, write_end;
   file::pipe(read_end, write_end);
   char c;
-  std::size_t size = UINT_MAX;
-  if (sizeof(unsigned) != sizeof(std::size_t)) ++size;
+  size_t size = UINT_MAX;
+  if (sizeof(unsigned) != sizeof(size_t)) ++size;
   read_count = 1;
   read_nbyte = 0;
   EXPECT_THROW(read_end.read(&c, size), fmt::system_error);
@@ -326,15 +329,15 @@
   file read_end, write_end;
   file::pipe(read_end, write_end);
   char c;
-  std::size_t size = UINT_MAX;
-  if (sizeof(unsigned) != sizeof(std::size_t)) ++size;
+  size_t size = UINT_MAX;
+  if (sizeof(unsigned) != sizeof(size_t)) ++size;
   write_count = 1;
   write_nbyte = 0;
   EXPECT_THROW(write_end.write(&c, size), fmt::system_error);
   write_count = 0;
   EXPECT_EQ(UINT_MAX, write_nbyte);
 }
-#endif
+#  endif
 
 TEST(FileTest, DupNoRetry) {
   int stdout_fd = FMT_POSIX(fileno(stdout));
@@ -359,11 +362,11 @@
   error_code ec;
   dup2_count = 1;
   f1.dup2(f2.descriptor(), ec);
-#ifndef _WIN32
+#  ifndef _WIN32
   EXPECT_EQ(4, dup2_count);
-#else
+#  else
   EXPECT_EQ(EINTR, ec.get());
-#endif
+#  endif
   dup2_count = 0;
 }
 
@@ -385,15 +388,15 @@
 }
 
 TEST(BufferedFileTest, OpenRetry) {
-  write_file("test", "there must be something here");
+  write_file("temp", "there must be something here");
   std::unique_ptr<buffered_file> f{nullptr};
-  EXPECT_RETRY(f.reset(new buffered_file("test", "r")), fopen,
-               "cannot open file test");
-#ifndef _WIN32
+  EXPECT_RETRY(f.reset(new buffered_file("temp", "r")), fopen,
+               "cannot open file temp");
+#  ifndef _WIN32
   char c = 0;
   if (fread(&c, 1, 1, f->get()) < 1)
     throw fmt::system_error(errno, "fread failed");
-#endif
+#  endif
 }
 
 TEST(BufferedFileTest, CloseNoRetryInDtor) {
@@ -401,14 +404,15 @@
   file::pipe(read_end, write_end);
   std::unique_ptr<buffered_file> f(new buffered_file(read_end.fdopen("r")));
   int saved_fclose_count = 0;
-  EXPECT_WRITE(stderr,
-               {
-                 fclose_count = 1;
-                 f.reset(nullptr);
-                 saved_fclose_count = fclose_count;
-                 fclose_count = 0;
-               },
-               format_system_error(EINTR, "cannot close file") + "\n");
+  EXPECT_WRITE(
+      stderr,
+      {
+        fclose_count = 1;
+        f.reset(nullptr);
+        saved_fclose_count = fclose_count;
+        fclose_count = 0;
+      },
+      format_system_error(EINTR, "cannot close file") + "\n");
   EXPECT_EQ(2, saved_fclose_count);
 }
 
@@ -433,33 +437,33 @@
 }
 #endif  // FMT_USE_FCNTL
 
-struct TestMock {
-  static TestMock* instance;
-} * TestMock::instance;
+struct test_mock {
+  static test_mock* instance;
+} * test_mock::instance;
 
 TEST(ScopedMock, Scope) {
   {
-    ScopedMock<TestMock> mock;
-    EXPECT_EQ(&mock, TestMock::instance);
-    TestMock& copy = mock;
+    ScopedMock<test_mock> mock;
+    EXPECT_EQ(&mock, test_mock::instance);
+    test_mock& copy = mock;
     static_cast<void>(copy);
   }
-  EXPECT_EQ(nullptr, TestMock::instance);
+  EXPECT_EQ(nullptr, test_mock::instance);
 }
 
 #ifdef FMT_LOCALE
 
-typedef fmt::Locale::type LocaleType;
+typedef fmt::locale::type locale_type;
 
-struct LocaleMock {
-  static LocaleMock* instance;
-  MOCK_METHOD3(newlocale, LocaleType(int category_mask, const char* locale,
-                                     LocaleType base));
-  MOCK_METHOD1(freelocale, void(LocaleType locale));
+struct locale_mock {
+  static locale_mock* instance;
+  MOCK_METHOD3(newlocale, locale_type(int category_mask, const char* locale,
+                                      locale_type base));
+  MOCK_METHOD1(freelocale, void(locale_type locale));
 
   MOCK_METHOD3(strtod_l,
-               double(const char* nptr, char** endptr, LocaleType locale));
-} * LocaleMock::instance;
+               double(const char* nptr, char** endptr, locale_type locale));
+} * locale_mock::instance;
 
 #  ifdef _MSC_VER
 #    pragma warning(push)
@@ -470,15 +474,15 @@
 #    endif
 
 _locale_t _create_locale(int category, const char* locale) {
-  return LocaleMock::instance->newlocale(category, locale, 0);
+  return locale_mock::instance->newlocale(category, locale, 0);
 }
 
 void _free_locale(_locale_t locale) {
-  LocaleMock::instance->freelocale(locale);
+  locale_mock::instance->freelocale(locale);
 }
 
 double _strtod_l(const char* nptr, char** endptr, _locale_t locale) {
-  return LocaleMock::instance->strtod_l(nptr, endptr, locale);
+  return locale_mock::instance->strtod_l(nptr, endptr, locale);
 }
 #    ifdef __clang__
 #      pragma clang diagnostic pop
@@ -492,11 +496,6 @@
 #    define FMT_LOCALE_THROW
 #  endif
 
-LocaleType newlocale(int category_mask, const char* locale,
-                     LocaleType base) FMT_LOCALE_THROW {
-  return LocaleMock::instance->newlocale(category_mask, locale, base);
-}
-
 #  if defined(__APPLE__) || \
       (defined(__FreeBSD__) && __FreeBSD_version < 1200002)
 typedef int FreeLocaleResult;
@@ -504,49 +503,55 @@
 typedef void FreeLocaleResult;
 #  endif
 
-FreeLocaleResult freelocale(LocaleType locale) FMT_LOCALE_THROW {
-  LocaleMock::instance->freelocale(locale);
+FreeLocaleResult freelocale(locale_type locale) FMT_LOCALE_THROW {
+  locale_mock::instance->freelocale(locale);
   return FreeLocaleResult();
 }
 
 double strtod_l(const char* nptr, char** endptr,
-                LocaleType locale) FMT_LOCALE_THROW {
-  return LocaleMock::instance->strtod_l(nptr, endptr, locale);
+                locale_type locale) FMT_LOCALE_THROW {
+  return locale_mock::instance->strtod_l(nptr, endptr, locale);
 }
 
 #  undef FMT_LOCALE_THROW
 
-TEST(LocaleTest, LocaleMock) {
-  ScopedMock<LocaleMock> mock;
-  LocaleType locale = reinterpret_cast<LocaleType>(11);
-  EXPECT_CALL(mock, newlocale(222, StrEq("foo"), locale));
-  newlocale(222, "foo", locale);
+#  ifndef _WIN32
+locale_t test::newlocale(int category_mask, const char* locale, locale_t base) {
+  return locale_mock::instance->newlocale(category_mask, locale, base);
 }
 
+TEST(LocaleTest, LocaleMock) {
+  ScopedMock<locale_mock> mock;
+  locale_type locale = reinterpret_cast<locale_type>(11);
+  EXPECT_CALL(mock, newlocale(222, StrEq("foo"), locale));
+  FMT_SYSTEM(newlocale(222, "foo", locale));
+}
+#  endif
+
 TEST(LocaleTest, Locale) {
 #  ifndef LC_NUMERIC_MASK
   enum { LC_NUMERIC_MASK = LC_NUMERIC };
 #  endif
-  ScopedMock<LocaleMock> mock;
-  LocaleType impl = reinterpret_cast<LocaleType>(42);
+  ScopedMock<locale_mock> mock;
+  locale_type impl = reinterpret_cast<locale_type>(42);
   EXPECT_CALL(mock, newlocale(LC_NUMERIC_MASK, StrEq("C"), nullptr))
       .WillOnce(Return(impl));
   EXPECT_CALL(mock, freelocale(impl));
-  fmt::Locale locale;
-  EXPECT_EQ(impl, locale.get());
+  fmt::locale loc;
+  EXPECT_EQ(impl, loc.get());
 }
 
 TEST(LocaleTest, Strtod) {
-  ScopedMock<LocaleMock> mock;
+  ScopedMock<locale_mock> mock;
   EXPECT_CALL(mock, newlocale(_, _, _))
-      .WillOnce(Return(reinterpret_cast<LocaleType>(42)));
+      .WillOnce(Return(reinterpret_cast<locale_type>(42)));
   EXPECT_CALL(mock, freelocale(_));
-  fmt::Locale locale;
+  fmt::locale loc;
   const char* str = "4.2";
   char end = 'x';
-  EXPECT_CALL(mock, strtod_l(str, _, locale.get()))
+  EXPECT_CALL(mock, strtod_l(str, _, loc.get()))
       .WillOnce(testing::DoAll(testing::SetArgPointee<1>(&end), Return(777)));
-  EXPECT_EQ(777, locale.strtod(str));
+  EXPECT_EQ(777, loc.strtod(str));
   EXPECT_EQ(&end, str);
 }
 
diff --git a/test/posix-mock.h b/test/posix-mock.h
index 028aeee..e76af70 100644
--- a/test/posix-mock.h
+++ b/test/posix-mock.h
@@ -9,7 +9,11 @@
 #define FMT_POSIX_TEST_H
 
 #include <errno.h>
+#include <locale.h>
 #include <stdio.h>
+#ifdef __APPLE__
+#  include <xlocale.h>
+#endif
 
 #ifdef _WIN32
 #  include <windows.h>
@@ -62,6 +66,10 @@
 FILE* fopen(const char* filename, const char* mode);
 int fclose(FILE* stream);
 int(fileno)(FILE* stream);
+
+#if defined(FMT_LOCALE) && !defined(_WIN32)
+locale_t newlocale(int category_mask, const char* locale, locale_t base);
+#endif
 }  // namespace test
 
 #define FMT_SYSTEM(call) test::call
diff --git a/test/posix-test.cc b/test/posix-test.cc
deleted file mode 100644
index 24d211d..0000000
--- a/test/posix-test.cc
+++ /dev/null
@@ -1,382 +0,0 @@
-// Formatting library for C++ - tests of the C++ interface to POSIX functions
-//
-// Copyright (c) 2012 - present, Victor Zverovich
-// All rights reserved.
-//
-// For the license information refer to format.h.
-
-#include <cstdlib>  // std::exit
-#include <cstring>
-#include <memory>
-
-#include "fmt/posix.h"
-#include "gtest-extra.h"
-#include "util.h"
-
-#ifdef fileno
-#  undef fileno
-#endif
-
-using fmt::buffered_file;
-using fmt::error_code;
-
-#if FMT_USE_FCNTL
-
-using fmt::file;
-
-// Checks if the file is open by reading one character from it.
-static bool isopen(int fd) {
-  char buffer;
-  return FMT_POSIX(read(fd, &buffer, 1)) == 1;
-}
-
-static bool isclosed(int fd) {
-  char buffer;
-  std::streamsize result = 0;
-  SUPPRESS_ASSERT(result = FMT_POSIX(read(fd, &buffer, 1)));
-  return result == -1 && errno == EBADF;
-}
-
-// Opens a file for reading.
-static file open_file() {
-  file read_end, write_end;
-  file::pipe(read_end, write_end);
-  write_end.write(FILE_CONTENT, std::strlen(FILE_CONTENT));
-  write_end.close();
-  return read_end;
-}
-
-// Attempts to write a string to a file.
-static void write(file& f, fmt::string_view s) {
-  std::size_t num_chars_left = s.size();
-  const char* ptr = s.data();
-  do {
-    std::size_t count = f.write(ptr, num_chars_left);
-    ptr += count;
-    // We can't write more than size_t bytes since num_chars_left
-    // has type size_t.
-    num_chars_left -= count;
-  } while (num_chars_left != 0);
-}
-
-TEST(BufferedFileTest, DefaultCtor) {
-  buffered_file f;
-  EXPECT_TRUE(f.get() == nullptr);
-}
-
-TEST(BufferedFileTest, MoveCtor) {
-  buffered_file bf = open_buffered_file();
-  FILE* fp = bf.get();
-  EXPECT_TRUE(fp != nullptr);
-  buffered_file bf2(std::move(bf));
-  EXPECT_EQ(fp, bf2.get());
-  EXPECT_TRUE(bf.get() == nullptr);
-}
-
-TEST(BufferedFileTest, MoveAssignment) {
-  buffered_file bf = open_buffered_file();
-  FILE* fp = bf.get();
-  EXPECT_TRUE(fp != nullptr);
-  buffered_file bf2;
-  bf2 = std::move(bf);
-  EXPECT_EQ(fp, bf2.get());
-  EXPECT_TRUE(bf.get() == nullptr);
-}
-
-TEST(BufferedFileTest, MoveAssignmentClosesFile) {
-  buffered_file bf = open_buffered_file();
-  buffered_file bf2 = open_buffered_file();
-  int old_fd = bf2.fileno();
-  bf2 = std::move(bf);
-  EXPECT_TRUE(isclosed(old_fd));
-}
-
-TEST(BufferedFileTest, MoveFromTemporaryInCtor) {
-  FILE* fp = nullptr;
-  buffered_file f(open_buffered_file(&fp));
-  EXPECT_EQ(fp, f.get());
-}
-
-TEST(BufferedFileTest, MoveFromTemporaryInAssignment) {
-  FILE* fp = nullptr;
-  buffered_file f;
-  f = open_buffered_file(&fp);
-  EXPECT_EQ(fp, f.get());
-}
-
-TEST(BufferedFileTest, MoveFromTemporaryInAssignmentClosesFile) {
-  buffered_file f = open_buffered_file();
-  int old_fd = f.fileno();
-  f = open_buffered_file();
-  EXPECT_TRUE(isclosed(old_fd));
-}
-
-TEST(BufferedFileTest, CloseFileInDtor) {
-  int fd = 0;
-  {
-    buffered_file f = open_buffered_file();
-    fd = f.fileno();
-  }
-  EXPECT_TRUE(isclosed(fd));
-}
-
-TEST(BufferedFileTest, CloseErrorInDtor) {
-  std::unique_ptr<buffered_file> f(new buffered_file(open_buffered_file()));
-  EXPECT_WRITE(stderr,
-               {
-                 // The close function must be called inside EXPECT_WRITE,
-                 // otherwise the system may recycle closed file descriptor when
-                 // redirecting the output in EXPECT_STDERR and the second close
-                 // will break output redirection.
-                 FMT_POSIX(close(f->fileno()));
-                 SUPPRESS_ASSERT(f.reset(nullptr));
-               },
-               format_system_error(EBADF, "cannot close file") + "\n");
-}
-
-TEST(BufferedFileTest, Close) {
-  buffered_file f = open_buffered_file();
-  int fd = f.fileno();
-  f.close();
-  EXPECT_TRUE(f.get() == nullptr);
-  EXPECT_TRUE(isclosed(fd));
-}
-
-TEST(BufferedFileTest, CloseError) {
-  buffered_file f = open_buffered_file();
-  FMT_POSIX(close(f.fileno()));
-  EXPECT_SYSTEM_ERROR_NOASSERT(f.close(), EBADF, "cannot close file");
-  EXPECT_TRUE(f.get() == nullptr);
-}
-
-TEST(BufferedFileTest, Fileno) {
-  buffered_file f;
-#ifndef __COVERITY__
-  // fileno on a null FILE pointer either crashes or returns an error.
-  // Disable Coverity because this is intentional.
-  EXPECT_DEATH_IF_SUPPORTED(
-      {
-        try {
-          f.fileno();
-        } catch (const fmt::system_error&) {
-          std::exit(1);
-        }
-      },
-      "");
-#endif
-  f = open_buffered_file();
-  EXPECT_TRUE(f.fileno() != -1);
-  file copy = file::dup(f.fileno());
-  EXPECT_READ(copy, FILE_CONTENT);
-}
-
-TEST(FileTest, DefaultCtor) {
-  file f;
-  EXPECT_EQ(-1, f.descriptor());
-}
-
-TEST(FileTest, OpenBufferedFileInCtor) {
-  FILE* fp = safe_fopen("test-file", "w");
-  std::fputs(FILE_CONTENT, fp);
-  std::fclose(fp);
-  file f("test-file", file::RDONLY);
-  ASSERT_TRUE(isopen(f.descriptor()));
-}
-
-TEST(FileTest, OpenBufferedFileError) {
-  EXPECT_SYSTEM_ERROR(file("nonexistent", file::RDONLY), ENOENT,
-                      "cannot open file nonexistent");
-}
-
-TEST(FileTest, MoveCtor) {
-  file f = open_file();
-  int fd = f.descriptor();
-  EXPECT_NE(-1, fd);
-  file f2(std::move(f));
-  EXPECT_EQ(fd, f2.descriptor());
-  EXPECT_EQ(-1, f.descriptor());
-}
-
-TEST(FileTest, MoveAssignment) {
-  file f = open_file();
-  int fd = f.descriptor();
-  EXPECT_NE(-1, fd);
-  file f2;
-  f2 = std::move(f);
-  EXPECT_EQ(fd, f2.descriptor());
-  EXPECT_EQ(-1, f.descriptor());
-}
-
-TEST(FileTest, MoveAssignmentClosesFile) {
-  file f = open_file();
-  file f2 = open_file();
-  int old_fd = f2.descriptor();
-  f2 = std::move(f);
-  EXPECT_TRUE(isclosed(old_fd));
-}
-
-static file OpenBufferedFile(int& fd) {
-  file f = open_file();
-  fd = f.descriptor();
-  return f;
-}
-
-TEST(FileTest, MoveFromTemporaryInCtor) {
-  int fd = 0xdead;
-  file f(OpenBufferedFile(fd));
-  EXPECT_EQ(fd, f.descriptor());
-}
-
-TEST(FileTest, MoveFromTemporaryInAssignment) {
-  int fd = 0xdead;
-  file f;
-  f = OpenBufferedFile(fd);
-  EXPECT_EQ(fd, f.descriptor());
-}
-
-TEST(FileTest, MoveFromTemporaryInAssignmentClosesFile) {
-  int fd = 0xdead;
-  file f = open_file();
-  int old_fd = f.descriptor();
-  f = OpenBufferedFile(fd);
-  EXPECT_TRUE(isclosed(old_fd));
-}
-
-TEST(FileTest, CloseFileInDtor) {
-  int fd = 0;
-  {
-    file f = open_file();
-    fd = f.descriptor();
-  }
-  EXPECT_TRUE(isclosed(fd));
-}
-
-TEST(FileTest, CloseErrorInDtor) {
-  std::unique_ptr<file> f(new file(open_file()));
-  EXPECT_WRITE(stderr,
-               {
-                 // The close function must be called inside EXPECT_WRITE,
-                 // otherwise the system may recycle closed file descriptor when
-                 // redirecting the output in EXPECT_STDERR and the second close
-                 // will break output redirection.
-                 FMT_POSIX(close(f->descriptor()));
-                 SUPPRESS_ASSERT(f.reset(nullptr));
-               },
-               format_system_error(EBADF, "cannot close file") + "\n");
-}
-
-TEST(FileTest, Close) {
-  file f = open_file();
-  int fd = f.descriptor();
-  f.close();
-  EXPECT_EQ(-1, f.descriptor());
-  EXPECT_TRUE(isclosed(fd));
-}
-
-TEST(FileTest, CloseError) {
-  file f = open_file();
-  FMT_POSIX(close(f.descriptor()));
-  EXPECT_SYSTEM_ERROR_NOASSERT(f.close(), EBADF, "cannot close file");
-  EXPECT_EQ(-1, f.descriptor());
-}
-
-TEST(FileTest, Read) {
-  file f = open_file();
-  EXPECT_READ(f, FILE_CONTENT);
-}
-
-TEST(FileTest, ReadError) {
-  file f("test-file", file::WRONLY);
-  char buf;
-  // We intentionally read from a file opened in the write-only mode to
-  // cause error.
-  EXPECT_SYSTEM_ERROR(f.read(&buf, 1), EBADF, "cannot read from file");
-}
-
-TEST(FileTest, Write) {
-  file read_end, write_end;
-  file::pipe(read_end, write_end);
-  write(write_end, "test");
-  write_end.close();
-  EXPECT_READ(read_end, "test");
-}
-
-TEST(FileTest, WriteError) {
-  file f("test-file", file::RDONLY);
-  // We intentionally write to a file opened in the read-only mode to
-  // cause error.
-  EXPECT_SYSTEM_ERROR(f.write(" ", 1), EBADF, "cannot write to file");
-}
-
-TEST(FileTest, Dup) {
-  file f = open_file();
-  file copy = file::dup(f.descriptor());
-  EXPECT_NE(f.descriptor(), copy.descriptor());
-  EXPECT_EQ(FILE_CONTENT, read(copy, std::strlen(FILE_CONTENT)));
-}
-
-#ifndef __COVERITY__
-TEST(FileTest, DupError) {
-  int value = -1;
-  EXPECT_SYSTEM_ERROR_NOASSERT(file::dup(value), EBADF,
-                               "cannot duplicate file descriptor -1");
-}
-#endif
-
-TEST(FileTest, Dup2) {
-  file f = open_file();
-  file copy = open_file();
-  f.dup2(copy.descriptor());
-  EXPECT_NE(f.descriptor(), copy.descriptor());
-  EXPECT_READ(copy, FILE_CONTENT);
-}
-
-TEST(FileTest, Dup2Error) {
-  file f = open_file();
-  EXPECT_SYSTEM_ERROR_NOASSERT(
-      f.dup2(-1), EBADF,
-      fmt::format("cannot duplicate file descriptor {} to -1", f.descriptor()));
-}
-
-TEST(FileTest, Dup2NoExcept) {
-  file f = open_file();
-  file copy = open_file();
-  error_code ec;
-  f.dup2(copy.descriptor(), ec);
-  EXPECT_EQ(ec.get(), 0);
-  EXPECT_NE(f.descriptor(), copy.descriptor());
-  EXPECT_READ(copy, FILE_CONTENT);
-}
-
-TEST(FileTest, Dup2NoExceptError) {
-  file f = open_file();
-  error_code ec;
-  SUPPRESS_ASSERT(f.dup2(-1, ec));
-  EXPECT_EQ(EBADF, ec.get());
-}
-
-TEST(FileTest, Pipe) {
-  file read_end, write_end;
-  file::pipe(read_end, write_end);
-  EXPECT_NE(-1, read_end.descriptor());
-  EXPECT_NE(-1, write_end.descriptor());
-  write(write_end, "test");
-  EXPECT_READ(read_end, "test");
-}
-
-TEST(FileTest, Fdopen) {
-  file read_end, write_end;
-  file::pipe(read_end, write_end);
-  int read_fd = read_end.descriptor();
-  EXPECT_EQ(read_fd, FMT_POSIX(fileno(read_end.fdopen("r").get())));
-}
-
-#ifdef FMT_LOCALE
-TEST(LocaleTest, Strtod) {
-  fmt::Locale locale;
-  const char *start = "4.2", *ptr = start;
-  EXPECT_EQ(4.2, locale.strtod(ptr));
-  EXPECT_EQ(start + 3, ptr);
-}
-#endif
-#endif  // FMT_USE_FCNTL
\ No newline at end of file
diff --git a/test/printf-test.cc b/test/printf-test.cc
index 2d68fab..ccd72dc 100644
--- a/test/printf-test.cc
+++ b/test/printf-test.cc
@@ -5,18 +5,19 @@
 //
 // For the license information refer to format.h.
 
+#include "fmt/printf.h"
+
 #include <cctype>
 #include <climits>
 #include <cstring>
 
 #include "fmt/core.h"
-#include "fmt/printf.h"
 #include "gtest-extra.h"
 #include "util.h"
 
 using fmt::format;
 using fmt::format_error;
-using fmt::internal::max_value;
+using fmt::detail::max_value;
 
 const unsigned BIG_NUM = INT_MAX + 1u;
 
@@ -112,14 +113,13 @@
 
 TEST(PrintfTest, InvalidArgIndex) {
   EXPECT_THROW_MSG(test_sprintf("%0$d", 42), format_error,
-                   "argument index out of range");
+                   "argument not found");
   EXPECT_THROW_MSG(test_sprintf("%2$d", 42), format_error,
-                   "argument index out of range");
+                   "argument not found");
   EXPECT_THROW_MSG(test_sprintf(format("%{}$d", INT_MAX), 42), format_error,
-                   "argument index out of range");
+                   "argument not found");
 
-  EXPECT_THROW_MSG(test_sprintf("%2$", 42), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(test_sprintf("%2$", 42), format_error, "argument not found");
   EXPECT_THROW_MSG(test_sprintf(format("%{}$d", BIG_NUM), 42), format_error,
                    "number is too big");
 }
@@ -139,8 +139,11 @@
 
   EXPECT_PRINTF("+00042", "%00+6d", 42);
 
+  EXPECT_PRINTF("   42", "%05.d", 42);
+  EXPECT_PRINTF(" 0042", "%05.4d", 42);
+
   // '0' flag is ignored for non-numeric types.
-  EXPECT_PRINTF("0000x", "%05c", 'x');
+  EXPECT_PRINTF("    x", "%05c", 'x');
 }
 
 TEST(PrintfTest, PlusFlag) {
@@ -151,11 +154,38 @@
 
   // '+' flag is ignored for non-numeric types.
   EXPECT_PRINTF("x", "%+c", 'x');
+
+  // '+' flag wins over space flag
+  EXPECT_PRINTF("+42", "%+ d", 42);
+  EXPECT_PRINTF("-42", "%+ d", -42);
+  EXPECT_PRINTF("+42", "% +d", 42);
+  EXPECT_PRINTF("-42", "% +d", -42);
+  EXPECT_PRINTF("+0042", "% +05d", 42);
+  EXPECT_PRINTF("+0042", "%0+ 5d", 42);
+
+  // '+' flag and space flag are both ignored for non-numeric types.
+  EXPECT_PRINTF("x", "%+ c", 'x');
+  EXPECT_PRINTF("x", "% +c", 'x');
 }
 
 TEST(PrintfTest, MinusFlag) {
   EXPECT_PRINTF("abc  ", "%-5s", "abc");
   EXPECT_PRINTF("abc  ", "%0--5s", "abc");
+
+  EXPECT_PRINTF("7    ", "%-5d", 7);
+  EXPECT_PRINTF("97   ", "%-5hhi", 'a');
+  EXPECT_PRINTF("a    ", "%-5c", 'a');
+
+  // '0' flag is ignored if '-' flag is given
+  EXPECT_PRINTF("7    ", "%-05d", 7);
+  EXPECT_PRINTF("7    ", "%0-5d", 7);
+  EXPECT_PRINTF("a    ", "%-05c", 'a');
+  EXPECT_PRINTF("a    ", "%0-5c", 'a');
+  EXPECT_PRINTF("97   ", "%-05hhi", 'a');
+  EXPECT_PRINTF("97   ", "%0-5hhi", 'a');
+
+  // '-' and space flag don't interfere
+  EXPECT_PRINTF(" 42", "%- d", 42);
 }
 
 TEST(PrintfTest, SpaceFlag) {
@@ -221,8 +251,7 @@
   EXPECT_EQ("42   ", test_sprintf("%*d", -5, 42));
   EXPECT_THROW_MSG(test_sprintf("%*d", 5.0, 42), format_error,
                    "width is not integer");
-  EXPECT_THROW_MSG(test_sprintf("%*d"), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(test_sprintf("%*d"), format_error, "argument not found");
   EXPECT_THROW_MSG(test_sprintf("%*d", BIG_NUM, 42), format_error,
                    "number is too big");
 }
@@ -258,6 +287,11 @@
   EXPECT_PRINTF(buffer, "%.3a", 1234.5678);
 }
 
+TEST(PrintfTest, StringPrecision) {
+  char test[] = {'H', 'e', 'l', 'l', 'o'};
+  EXPECT_EQ(fmt::sprintf("%.4s", test), "Hell");
+}
+
 TEST(PrintfTest, IgnorePrecisionForNonNumericArg) {
   EXPECT_PRINTF("abc", "%.5s", "abc");
 }
@@ -267,8 +301,7 @@
   EXPECT_EQ("42", test_sprintf("%.*d", -5, 42));
   EXPECT_THROW_MSG(test_sprintf("%.*d", 5.0, 42), format_error,
                    "precision is not integer");
-  EXPECT_THROW_MSG(test_sprintf("%.*d"), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(test_sprintf("%.*d"), format_error, "argument not found");
   EXPECT_THROW_MSG(test_sprintf("%.*d", BIG_NUM, 42), format_error,
                    "number is too big");
   if (sizeof(long long) != sizeof(int)) {
@@ -297,18 +330,18 @@
   unsigned long long unsigned_value = 0;
   // Apply integer promotion to the argument.
   unsigned long long max = max_value<U>();
-  using fmt::internal::const_check;
+  using fmt::detail::const_check;
   if (const_check(max <= static_cast<unsigned>(max_value<int>()))) {
     signed_value = static_cast<int>(value);
-    unsigned_value = static_cast<unsigned>(value);
+    unsigned_value = static_cast<unsigned long long>(value);
   } else if (const_check(max <= max_value<unsigned>())) {
     signed_value = static_cast<unsigned>(value);
-    unsigned_value = static_cast<unsigned>(value);
+    unsigned_value = static_cast<unsigned long long>(value);
   }
   if (sizeof(U) <= sizeof(int) && sizeof(int) < sizeof(T)) {
     signed_value = static_cast<long long>(value);
-    unsigned_value =
-        static_cast<typename std::make_unsigned<unsigned>::type>(value);
+    unsigned_value = static_cast<unsigned long long>(
+        static_cast<typename std::make_unsigned<unsigned>::type>(value));
   } else {
     signed_value = static_cast<typename make_signed<T>::type>(value);
     unsigned_value = static_cast<typename std::make_unsigned<T>::type>(value);
@@ -366,7 +399,7 @@
   TestLength<long long>("ll");
   TestLength<unsigned long long>("ll");
   TestLength<intmax_t>("j");
-  TestLength<std::size_t>("z");
+  TestLength<size_t>("z");
   TestLength<std::ptrdiff_t>("t");
   long double max = max_value<long double>();
   EXPECT_PRINTF(fmt::format("{:.6}", max), "%g", max);
@@ -446,6 +479,12 @@
   EXPECT_PRINTF(L"    (null)", L"%10s", null_wstr);
 }
 
+TEST(PrintfTest, UCharString) {
+  unsigned char str[] = "test";
+  unsigned char* pstr = str;
+  EXPECT_EQ("test", fmt::sprintf("%s", pstr));
+}
+
 TEST(PrintfTest, Pointer) {
   int n;
   void* p = &n;
@@ -473,9 +512,13 @@
   // TODO: test %n
 }
 
-enum E { A = 42 };
+enum test_enum { answer = 42 };
 
-TEST(PrintfTest, Enum) { EXPECT_PRINTF("42", "%d", A); }
+TEST(PrintfTest, Enum) {
+  EXPECT_PRINTF("42", "%d", answer);
+  volatile test_enum volatile_enum = answer;
+  EXPECT_PRINTF("42", "%d", volatile_enum);
+}
 
 #if FMT_USE_FCNTL
 TEST(PrintfTest, Examples) {
@@ -564,50 +607,22 @@
 #endif
 }
 
-typedef fmt::printf_arg_formatter<fmt::buffer_range<char>> formatter_t;
-typedef fmt::basic_printf_context<formatter_t::iterator, char> context_t;
+TEST(PrintfTest, PrintfDetermineOutputSize) {
+  using backit = std::back_insert_iterator<std::vector<char>>;
+  using truncated_printf_context =
+      fmt::basic_printf_context<fmt::detail::truncating_iterator<backit>, char>;
 
-// A custom printf argument formatter that doesn't print `-` for floating-point
-// values rounded to 0.
-class custom_printf_arg_formatter : public formatter_t {
- public:
-  using formatter_t::iterator;
+  auto v = std::vector<char>{};
+  auto it = std::back_inserter(v);
 
-  custom_printf_arg_formatter(formatter_t::iterator iter,
-                              formatter_t::format_specs& specs, context_t& ctx)
-      : formatter_t(iter, specs, ctx) {}
+  const auto format_string = "%s";
+  const auto format_arg = "Hello";
+  const auto expected_size = fmt::sprintf(format_string, format_arg).size();
 
-  using formatter_t::operator();
-
-#if FMT_MSC_VER > 0 && FMT_MSC_VER <= 1804
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  iterator operator()(T value){
-#else
-  iterator operator()(double value) {
-#endif
-      // Comparing a float to 0.0 is safe.
-      if (round(value * pow(10, specs()->precision)) == 0.0) value = 0;
-  return formatter_t::operator()(value);
-}
-};
-
-typedef fmt::basic_format_args<context_t> format_args_t;
-
-std::string custom_vformat(fmt::string_view format_str, format_args_t args) {
-  fmt::memory_buffer buffer;
-  fmt::vprintf<custom_printf_arg_formatter>(buffer, format_str, args);
-  return std::string(buffer.data(), buffer.size());
-}
-
-template <typename... Args>
-std::string custom_format(const char* format_str, const Args&... args) {
-  auto va = fmt::make_printf_args(args...);
-  return custom_vformat(format_str, {va});
-}
-
-TEST(PrintfTest, CustomFormat) {
-  EXPECT_EQ("0.00", custom_format("%.2f", -.00001));
-  EXPECT_EQ("0.00", custom_format("%.2f", .00001));
-  EXPECT_EQ("1.00", custom_format("%.2f", 1.00001));
-  EXPECT_EQ("-1.00", custom_format("%.2f", -1.00001));
+  EXPECT_EQ((truncated_printf_context(
+                 fmt::detail::truncating_iterator<backit>(it, 0), format_string,
+                 fmt::make_format_args<truncated_printf_context>(format_arg))
+                 .format()
+                 .count()),
+            expected_size);
 }
diff --git a/test/ranges-test.cc b/test/ranges-test.cc
index 265f9ac..63f9e6e 100644
--- a/test/ranges-test.cc
+++ b/test/ranges-test.cc
@@ -10,6 +10,7 @@
 // {fmt} support for ranges, containers and types tuple interface.
 
 #include "fmt/ranges.h"
+
 #include "gtest.h"
 
 // Check if  'if constexpr' is supported.
@@ -44,15 +45,16 @@
 }
 
 TEST(RangesTest, FormatTuple) {
-  std::tuple<int64_t, float, std::string, char> tu1{42, 1.5f, "this is tuple",
-                                                    'i'};
-  EXPECT_EQ("(42, 1.5, \"this is tuple\", 'i')", fmt::format("{}", tu1));
+  std::tuple<int64_t, float, std::string, char> t{42, 1.5f, "this is tuple",
+                                                  'i'};
+  EXPECT_EQ("(42, 1.5, \"this is tuple\", 'i')", fmt::format("{}", t));
+  EXPECT_EQ("()", fmt::format("{}", std::tuple<>()));
 }
 
 TEST(RangesTest, JoinTuple) {
   // Value tuple args
   std::tuple<char, int, float> t1 = std::make_tuple('a', 1, 2.0f);
-  EXPECT_EQ("(a, 1, 2.0)", fmt::format("({})", fmt::join(t1, ", ")));
+  EXPECT_EQ("(a, 1, 2)", fmt::format("({})", fmt::join(t1, ", ")));
 
   // Testing lvalue tuple args
   int x = 4;
@@ -65,13 +67,19 @@
 
   // Single element tuple
   std::tuple<float> t4{4.0f};
-  EXPECT_EQ("4.0", fmt::format("{}", fmt::join(t4, "/")));
+  EXPECT_EQ("4", fmt::format("{}", fmt::join(t4, "/")));
+}
+
+TEST(RangesTest, JoinInitializerList) {
+  EXPECT_EQ("1, 2, 3", fmt::format("{}", fmt::join({1, 2, 3}, ", ")));
+  EXPECT_EQ("fmt rocks !",
+            fmt::format("{}", fmt::join({"fmt", "rocks", "!"}, " ")));
 }
 
 struct my_struct {
   int32_t i;
   std::string str;  // can throw
-  template <std::size_t N> decltype(auto) get() const noexcept {
+  template <size_t N> decltype(auto) get() const noexcept {
     if constexpr (N == 0)
       return i;
     else if constexpr (N == 1)
@@ -79,16 +87,15 @@
   }
 };
 
-template <std::size_t N> decltype(auto) get(const my_struct& s) noexcept {
+template <size_t N> decltype(auto) get(const my_struct& s) noexcept {
   return s.get<N>();
 }
 
 namespace std {
 
-template <>
-struct tuple_size<my_struct> : std::integral_constant<std::size_t, 2> {};
+template <> struct tuple_size<my_struct> : std::integral_constant<size_t, 2> {};
 
-template <std::size_t N> struct tuple_element<N, my_struct> {
+template <size_t N> struct tuple_element<N, my_struct> {
   using type = decltype(std::declval<my_struct>().get<N>());
 };
 
@@ -132,3 +139,65 @@
   EXPECT_EQ("foo", fmt::format("{}", string_like()));
 }
 #endif  // FMT_USE_STRING_VIEW
+
+struct zstring_sentinel {};
+
+bool operator==(const char* p, zstring_sentinel) { return *p == '\0'; }
+bool operator!=(const char* p, zstring_sentinel) { return *p != '\0'; }
+
+struct zstring {
+  const char* p;
+  const char* begin() const { return p; }
+  zstring_sentinel end() const { return {}; }
+};
+
+TEST(RangesTest, JoinSentinel) {
+  zstring hello{"hello"};
+  EXPECT_EQ("{'h', 'e', 'l', 'l', 'o'}", fmt::format("{}", hello));
+  EXPECT_EQ("h_e_l_l_o", fmt::format("{}", fmt::join(hello, "_")));
+}
+
+// A range that provides non-const only begin()/end() to test fmt::join handles
+// that
+//
+// Some ranges (eg those produced by range-v3's views::filter()) can cache
+// information during iteration so they only provide non-const begin()/end().
+template <typename T> class non_const_only_range {
+ private:
+  std::vector<T> vec;
+
+ public:
+  using const_iterator = typename ::std::vector<T>::const_iterator;
+
+  template <typename... Args>
+  explicit non_const_only_range(Args&&... args)
+      : vec(::std::forward<Args>(args)...) {}
+
+  const_iterator begin() { return vec.begin(); }
+  const_iterator end() { return vec.end(); }
+};
+
+TEST(RangesTest, JoinRange) {
+  non_const_only_range<int> x(3u, 0);
+  EXPECT_EQ("0,0,0", fmt::format("{}", fmt::join(x, ",")));
+  EXPECT_EQ(
+      "0,0,0",
+      fmt::format("{}", fmt::join(non_const_only_range<int>(3u, 0), ",")));
+
+  std::vector<int> y(3u, 0);
+  EXPECT_EQ("0,0,0", fmt::format("{}", fmt::join(y, ",")));
+  EXPECT_EQ("0,0,0",
+            fmt::format("{}", fmt::join(std::vector<int>(3u, 0), ",")));
+
+  const std::vector<int> z(3u, 0);
+  EXPECT_EQ("0,0,0", fmt::format("{}", fmt::join(z, ",")));
+}
+
+#if !FMT_MSC_VER || FMT_MSC_VER >= 1927
+struct unformattable {};
+
+TEST(RangesTest, UnformattableRange) {
+  EXPECT_FALSE((fmt::has_formatter<std::vector<unformattable>,
+                                   fmt::format_context>::value));
+}
+#endif
diff --git a/test/scan-test.cc b/test/scan-test.cc
index 0b49fd9..962de54 100644
--- a/test/scan-test.cc
+++ b/test/scan-test.cc
@@ -5,12 +5,14 @@
 //
 // For the license information refer to format.h.
 
+#include "scan.h"
+
 #include <time.h>
+
 #include <climits>
 
 #include "gmock.h"
 #include "gtest-extra.h"
-#include "scan.h"
 
 TEST(ScanTest, ReadText) {
   fmt::string_view s = "foo";
@@ -73,7 +75,7 @@
     if (it != ctx.end() && *it == ':') ++it;
     auto end = it;
     while (end != ctx.end() && *end != '}') ++end;
-    format.reserve(internal::to_unsigned(end - it + 1));
+    format.reserve(detail::to_unsigned(end - it + 1));
     format.append(it, end);
     format.push_back('\0');
     return end;
diff --git a/test/scan.h b/test/scan.h
index 50ac094..de82067 100644
--- a/test/scan.h
+++ b/test/scan.h
@@ -6,6 +6,8 @@
 // For the license information refer to format.h.
 
 #include <array>
+#include <cassert>
+#include <climits>
 
 #include "fmt/format.h"
 
@@ -29,7 +31,7 @@
   FMT_CONSTEXPR iterator end() const { return format_.end(); }
 
   void advance_to(iterator it) {
-    format_.remove_prefix(internal::to_unsigned(it - begin()));
+    format_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 };
 
@@ -46,11 +48,11 @@
   iterator end() const { return begin() + input_.size(); }
 
   void advance_to(iterator it) {
-    input_.remove_prefix(internal::to_unsigned(it - begin()));
+    input_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 };
 
-namespace internal {
+namespace detail {
 enum class scan_type {
   none_type,
   int_type,
@@ -105,20 +107,20 @@
     ctx.advance_to(s.scan(*static_cast<T*>(arg), ctx));
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 struct scan_args {
   int size;
-  const internal::scan_arg* data;
+  const detail::scan_arg* data;
 
   template <size_t N>
-  scan_args(const std::array<internal::scan_arg, N>& store)
+  scan_args(const std::array<detail::scan_arg, N>& store)
       : size(N), data(store.data()) {
     static_assert(N < INT_MAX, "too many arguments");
   }
 };
 
-namespace internal {
+namespace detail {
 
 struct scan_handler : error_handler {
  private:
@@ -135,21 +137,20 @@
       char c = *it++;
       if (c < '0' || c > '9') on_error("invalid input");
       // TODO: check overflow
-      value = value * 10 + (c - '0');
+      value = value * 10 + static_cast<unsigned>(c - '0');
     }
     scan_ctx_.advance_to(it);
     return value;
   }
 
   template <typename T = int> T read_int() {
-    T value = 0;
     auto it = scan_ctx_.begin(), end = scan_ctx_.end();
     bool negative = it != end && *it == '-';
     if (negative) ++it;
     scan_ctx_.advance_to(it);
-    value = read_uint<typename std::make_unsigned<T>::type>();
-    if (negative) value = -value;
-    return value;
+    const auto value = read_uint<typename std::make_unsigned<T>::type>();
+    if (negative) return -static_cast<T>(value);
+    return static_cast<T>(value);
   }
 
  public:
@@ -159,7 +160,7 @@
   const char* pos() const { return scan_ctx_.begin(); }
 
   void on_text(const char* begin, const char* end) {
-    auto size = end - begin;
+    auto size = to_unsigned(end - begin);
     auto it = scan_ctx_.begin();
     if (it + size > scan_ctx_.end() ||
         !std::equal(begin, end, make_checked(it, size))) {
@@ -168,14 +169,15 @@
     scan_ctx_.advance_to(it + size);
   }
 
-  void on_arg_id() { on_arg_id(next_arg_id_++); }
-  void on_arg_id(int id) {
+  int on_arg_id() { return on_arg_id(next_arg_id_++); }
+  int on_arg_id(int id) {
     if (id >= args_.size) on_error("argument index out of range");
     arg_ = args_.data[id];
+    return id;
   }
-  void on_arg_id(string_view) { on_error("invalid format"); }
+  int on_arg_id(string_view) { return on_error("invalid format"), 0; }
 
-  void on_replacement_field(const char*) {
+  void on_replacement_field(int, const char*) {
     auto it = scan_ctx_.begin(), end = scan_ctx_.end();
     switch (arg_.type) {
     case scan_type::int_type:
@@ -197,7 +199,7 @@
     case scan_type::string_view_type: {
       auto s = it;
       while (it != end && *it != ' ') ++it;
-      *arg_.string_view = fmt::string_view(s, it - s);
+      *arg_.string_view = fmt::string_view(s, to_unsigned(it - s));
       scan_ctx_.advance_to(it);
       break;
     }
@@ -207,24 +209,24 @@
     }
   }
 
-  const char* on_format_specs(const char* begin, const char*) {
+  const char* on_format_specs(int, const char* begin, const char*) {
     if (arg_.type != scan_type::custom_type) return begin;
     parse_ctx_.advance_to(begin);
     arg_.custom.scan(arg_.custom.value, parse_ctx_, scan_ctx_);
     return parse_ctx_.begin();
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 template <typename... Args>
-std::array<internal::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
+std::array<detail::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
   return {{args...}};
 }
 
 string_view::iterator vscan(string_view input, string_view format_str,
                             scan_args args) {
-  internal::scan_handler h(format_str, input, args);
-  internal::parse_format_string<false>(format_str, h);
+  detail::scan_handler h(format_str, input, args);
+  detail::parse_format_string<false>(format_str, h);
   return input.begin() + (h.pos() - &*input.begin());
 }
 
diff --git a/test/std-format-test.cc b/test/std-format-test.cc
index a95f244..8bf4b6d 100644
--- a/test/std-format-test.cc
+++ b/test/std-format-test.cc
@@ -1,4 +1,5 @@
 #include <format>
+
 #include "gtest.h"
 
 TEST(StdFormatTest, Escaping) {
@@ -29,8 +30,8 @@
   string s4 = format("{:*^6}", 'x');  // s4 == "**x***"
   // Error: '=' with charT and no integer presentation type
   EXPECT_THROW(string s5 = format("{:=6}", 'x'), std::format_error);
-  string s6 = format("{:6d}", c);       // s6 == "   120"
-  string s7 = format("{:6}", true);     // s9 == "true  "
+  string s6 = format("{:6d}", c);    // s6 == "   120"
+  string s7 = format("{:6}", true);  // s9 == "true  "
   EXPECT_EQ(s0, "    42");
   EXPECT_EQ(s1, "x     ");
   EXPECT_EQ(s2, "x*****");
@@ -61,7 +62,7 @@
   string s0 = format("{}", 42);                       // s0 == "42"
   string s1 = format("{0:b} {0:d} {0:o} {0:x}", 42);  // s1 == "101010 42 52 2a"
   string s2 = format("{0:#x} {0:#X}", 42);            // s2 == "0x2a 0X2A"
-  string s3 = format("{:n}", 1234);  // s3 == "1234" (depends on the locale)
+  string s3 = format("{:L}", 1234);  // s3 == "1234" (depends on the locale)
   EXPECT_EQ(s0, "42");
   EXPECT_EQ(s1, "101010 42 52 2a");
   EXPECT_EQ(s2, "0x2a 0X2A");
@@ -123,7 +124,7 @@
           if constexpr (!is_integral_v<type> || is_same_v<type, bool>)
             throw format_error("width is not integral");
           // else if (value < 0 || value > numeric_limits<int>::max())
-          else if (fmt::internal::is_negative(value) ||
+          else if (fmt::detail::is_negative(value) ||
                    value > numeric_limits<int>::max())
             throw format_error("invalid width");
           else
diff --git a/test/test-assert.h b/test/test-assert.h
index c02dc0f..f613722 100644
--- a/test/test-assert.h
+++ b/test/test-assert.h
@@ -9,6 +9,7 @@
 #define FMT_TEST_ASSERT_H_
 
 #include <stdexcept>
+
 #include "gtest.h"
 
 class assertion_failure : public std::logic_error {
diff --git a/test/test-main.cc b/test/test-main.cc
index d911131..8db257d 100644
--- a/test/test-main.cc
+++ b/test/test-main.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include <cstdlib>
+
 #include "gtest.h"
 
 #ifdef _WIN32
diff --git a/test/util.cc b/test/util.cc
index e75bd45..d08dcbd 100644
--- a/test/util.cc
+++ b/test/util.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include "util.h"
+
 #include <cstring>
 
 void increment(char* s) {
diff --git a/test/util.h b/test/util.h
index 7aa9da2..24a5f4e 100644
--- a/test/util.h
+++ b/test/util.h
@@ -9,7 +9,7 @@
 #include <cstdio>
 #include <string>
 
-#include "fmt/posix.h"
+#include "fmt/os.h"
 
 enum { BUFFER_SIZE = 256 };
 
@@ -19,7 +19,7 @@
 #  define FMT_VSNPRINTF vsnprintf
 #endif
 
-template <std::size_t SIZE>
+template <size_t SIZE>
 void safe_sprintf(char (&buffer)[SIZE], const char* format, ...) {
   std::va_list args;
   va_start(args, format);