[libcxx] Capture configuration information when installing the libc++ headers
Summary:
Hi all,
This patch is a successor to D11963. However it has changed dramatically and I felt it would be best to start a new review thread.
Please read the design documentation added in this patch for a description of how it works.
Reviewers: mclow.lists, danalbert, jroelofs, EricWF
Subscribers: vkalintiris, rnk, ed, espositofulvio, asl, eugenis, cfe-commits
Differential Revision: http://reviews.llvm.org/D13407
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@250235 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0dc9381..41627ab 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -260,13 +260,6 @@
# Feature flags ===============================================================
define_if(MSVC -D_CRT_SECURE_NO_WARNINGS)
-define_if_not(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE -D_LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE)
-define_if_not(LIBCXX_ENABLE_STDIN -D_LIBCPP_HAS_NO_STDIN)
-define_if_not(LIBCXX_ENABLE_STDOUT -D_LIBCPP_HAS_NO_STDOUT)
-define_if_not(LIBCXX_ENABLE_THREADS -D_LIBCPP_HAS_NO_THREADS)
-define_if_not(LIBCXX_ENABLE_MONOTONIC_CLOCK -D_LIBCPP_HAS_NO_MONOTONIC_CLOCK)
-define_if_not(LIBCXX_ENABLE_THREAD_UNSAFE_C_FUNCTIONS -D_LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS)
-
# Sanitizer flags =============================================================
@@ -303,6 +296,22 @@
message(WARNING "LLVM_USE_SANITIZER is not supported on this platform.")
endif()
endif()
+
+# Configuration file flags =====================================================
+config_define_if_not(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE)
+config_define_if_not(LIBCXX_ENABLE_STDIN _LIBCPP_HAS_NO_STDIN)
+config_define_if_not(LIBCXX_ENABLE_STDOUT _LIBCPP_HAS_NO_STDOUT)
+config_define_if_not(LIBCXX_ENABLE_THREADS _LIBCPP_HAS_NO_THREADS)
+config_define_if_not(LIBCXX_ENABLE_MONOTONIC_CLOCK _LIBCPP_HAS_NO_MONOTONIC_CLOCK)
+config_define_if_not(LIBCXX_ENABLE_THREAD_UNSAFE_C_FUNCTIONS _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS)
+
+if (LIBCXX_NEEDS_SITE_CONFIG)
+ configure_file(
+ include/__config_site.in
+ ${LIBCXX_BINARY_DIR}/__config_site
+ @ONLY)
+endif()
+
#===============================================================================
# Setup Source Code And Tests
#===============================================================================
diff --git a/cmake/Modules/HandleLibcxxFlags.cmake b/cmake/Modules/HandleLibcxxFlags.cmake
index 223b7b7..a9e43ea 100644
--- a/cmake/Modules/HandleLibcxxFlags.cmake
+++ b/cmake/Modules/HandleLibcxxFlags.cmake
@@ -49,6 +49,22 @@
endif()
endmacro()
+macro(config_define_if condition def)
+ if (${condition})
+ set(${def} ON)
+ add_definitions(-D${def})
+ set(LIBCXX_NEEDS_SITE_CONFIG ON)
+ endif()
+endmacro()
+
+macro(config_define_if_not condition def)
+ if (NOT ${condition})
+ set(${def} ON)
+ add_definitions(-D${def})
+ set(LIBCXX_NEEDS_SITE_CONFIG ON)
+ endif()
+endmacro()
+
# Add a specified list of flags to both 'LIBCXX_COMPILE_FLAGS' and
# 'LIBCXX_LINK_FLAGS'.
macro(add_flags)
diff --git a/docs/DesignDocs/CapturingConfigInfo.rst b/docs/DesignDocs/CapturingConfigInfo.rst
new file mode 100644
index 0000000..0f16ca1
--- /dev/null
+++ b/docs/DesignDocs/CapturingConfigInfo.rst
@@ -0,0 +1,88 @@
+=======================================================
+Capturing configuration information during installation
+=======================================================
+
+.. contents::
+ :local:
+
+The Problem
+===========
+
+Currently the libc++ supports building the library with a number of different
+configuration options. Unfortunately all of that configuration information is
+lost when libc++ is installed. In order to support "persistent"
+configurations libc++ needs a mechanism to capture the configuration options
+in the INSTALLED headers.
+
+
+Design Goals
+============
+
+* The solution should not INSTALL any additional headers. We don't want an extra
+ #include slowing everybody down.
+
+* The solution should not unduly affect libc++ developers. The problem is limited
+ to installed versions of libc++ and the solution should be as well.
+
+* The solution should not modify any existing headers EXCEPT during installation.
+ It makes developers lives harder if they have to regenerate the libc++ headers
+ every time they are modified.
+
+* The solution should not make any of the libc++ headers dependant on
+ files generated by the build system. The headers should be able to compile
+ out of the box without any modification.
+
+* The solution should not have ANY effect on users who don't need special
+ configuration options. The vast majority of users will never need this so it
+ shouldn't cost them.
+
+
+The Solution
+============
+
+When you first configure libc++ using CMake we check to see if we need to
+capture any options. If we haven't been given any "persistent" options then
+we do NOTHING.
+
+Otherwise we create a custom installation rule that modifies the installed __config
+header. The rule first generates a dummy "__config_site" header containing the required
+#defines. The contents of the dummy header are then prependend to the installed
+__config header. By manually prepending the files we avoid the cost of an
+extra #include and we allow the __config header to be ignorant of the extra
+ configuration all together. An example "__config" header generated when
+-DLIBCXX_ENABLE_THREADS=OFF is given to CMake would look something like:
+
+.. code-block:: cpp
+
+ //===----------------------------------------------------------------------===//
+ //
+ // The LLVM Compiler Infrastructure
+ //
+ // This file is dual licensed under the MIT and the University of Illinois Open
+ // Source Licenses. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+
+ #ifndef _LIBCPP_CONFIG_SITE
+ #define _LIBCPP_CONFIG_SITE
+
+ /* #undef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE */
+ /* #undef _LIBCPP_HAS_NO_STDIN */
+ /* #undef _LIBCPP_HAS_NO_STDOUT */
+ #define _LIBCPP_HAS_NO_THREADS
+ /* #undef _LIBCPP_HAS_NO_MONOTONIC_CLOCK */
+ /* #undef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS */
+
+ #endif
+ // -*- C++ -*-
+ //===--------------------------- __config ---------------------------------===//
+ //
+ // The LLVM Compiler Infrastructure
+ //
+ // This file is dual licensed under the MIT and the University of Illinois Open
+ // Source Licenses. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+
+ #ifndef _LIBCPP_CONFIG
+ #define _LIBCPP_CONFIG
diff --git a/docs/index.rst b/docs/index.rst
index acd9229..f34979f 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -124,6 +124,12 @@
Design Documents
----------------
+.. toctree::
+ :maxdepth: 1
+
+ DesignDocs/CapturingConfigInfo
+
+
* `<atomic> design <http://libcxx.llvm.org/atomic_design.html>`_
* `<type_traits> design <http://libcxx.llvm.org/type_traits_design.html>`_
* `Status of debug mode <http://libcxx.llvm.org/debug_mode.html>`_
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index 7a7c229..e16dc8b 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -1,10 +1,12 @@
if (NOT LIBCXX_INSTALL_SUPPORT_HEADERS)
set(LIBCXX_SUPPORT_HEADER_PATTERN PATTERN "support" EXCLUDE)
endif()
+
set(LIBCXX_HEADER_PATTERN
PATTERN "*"
PATTERN "CMakeLists.txt" EXCLUDE
PATTERN ".svn" EXCLUDE
+ PATTERN "__config_site.in" EXCLUDE
${LIBCXX_SUPPORT_HEADER_PATTERN}
)
@@ -22,4 +24,29 @@
${LIBCXX_HEADER_PATTERN}
PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
)
+
+ if (LIBCXX_NEEDS_SITE_CONFIG)
+ set(UNIX_CAT cat)
+ if (WIN32)
+ set(UNIX_CAT type)
+ endif()
+ # Generate and install a custom __config header. The new header is created
+ # by prepending __config_site to the current __config header.
+ add_custom_command(OUTPUT ${LIBCXX_BINARY_DIR}/__generated_config
+ COMMAND ${CMAKE_COMMAND} -E copy ${LIBCXX_BINARY_DIR}/__config_site ${LIBCXX_BINARY_DIR}/__generated_config
+ COMMAND ${UNIX_CAT} ${LIBCXX_SOURCE_DIR}/include/__config >> ${LIBCXX_BINARY_DIR}/__generated_config
+ DEPENDS ${LIBCXX_SOURCE_DIR}/include/__config
+ ${LIBCXX_BINARY_DIR}/__config_site
+ )
+ # Add a target that executes the generation commands.
+ add_custom_target(generate_config_header ALL
+ DEPENDS ${LIBCXX_BINARY_DIR}/__generated_config)
+ # Install the generated header as __config.
+ install(FILES ${LIBCXX_BINARY_DIR}/__generated_config
+ DESTINATION include/c++/v1
+ PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
+ RENAME __config
+ COMPONENT libcxx)
+ endif()
+
endif()
diff --git a/include/__config_site.in b/include/__config_site.in
new file mode 100644
index 0000000..a248787
--- /dev/null
+++ b/include/__config_site.in
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_CONFIG_SITE
+#define _LIBCPP_CONFIG_SITE
+
+#cmakedefine _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
+#cmakedefine _LIBCPP_HAS_NO_STDIN
+#cmakedefine _LIBCPP_HAS_NO_STDOUT
+#cmakedefine _LIBCPP_HAS_NO_THREADS
+#cmakedefine _LIBCPP_HAS_NO_MONOTONIC_CLOCK
+#cmakedefine _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
+
+#endif
