patches/move-cxa-demangle-into-libcxxdemangle.patch

From cceb020e3497e1af208e546ac971e265f46d2f66 Mon Sep 17 00:00:00 2001
From: Ryan Prichard <rprichard@google.com>
Date: Mon, 25 Jul 2022 18:05:30 -0700
Subject: [PATCH] [libc++abi] Optionally move __cxa_demangle into
 libc++demangle.a

The motivation is to reduce the size of libc++.so on Android. The flag
is always used with LIBCXXABI_NON_DEMANGLING_TERMINATE.

Differential Revision: https://reviews.llvm.org/D139493
---
 libcxxabi/CMakeLists.txt     |  9 +++++++++
 libcxxabi/src/CMakeLists.txt | 25 ++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
index efe830bd2ad6..17fb41eda1a6 100644
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -79,6 +79,7 @@ option(LIBCXXABI_INSTALL_LIBRARY "Install the libc++abi library." ON)
 
 set(LIBCXXABI_SHARED_OUTPUT_NAME "c++abi" CACHE STRING "Output name for the shared libc++abi runtime library.")
 set(LIBCXXABI_STATIC_OUTPUT_NAME "c++abi" CACHE STRING "Output name for the static libc++abi runtime library.")
+set(LIBCXXABI_DEMANGLE_STATIC_OUTPUT_NAME "c++demangle" CACHE STRING "Output name for the optional libc++demangle runtime library.")
 
 set(LIBCXXABI_INSTALL_INCLUDE_DIR "${CMAKE_INSTALL_INCLUDEDIR}/c++/v1" CACHE STRING "Path to install the libc++abi headers at.")
 
@@ -123,6 +124,14 @@ option(LIBCXXABI_SILENT_TERMINATE "Set this to make the terminate handler defaul
 option(LIBCXXABI_NON_DEMANGLING_TERMINATE "Set this to make the terminate handler
 avoid demangling" OFF)
 
+# Omit __cxa_demangle to reduce the size of libc++[abi].so. Package it into a
+# separate static library for when it is actually needed.
+option(LIBCXXABI_STATIC_DEMANGLE_LIBRARY "Put __cxa_demangle into a separate static library" OFF)
+
+if (LIBCXXABI_STATIC_DEMANGLE_LIBRARY AND NOT LIBCXXABI_NON_DEMANGLING_TERMINATE)
+  message(FATAL_ERROR "libc++demangle is only supported when libc++abi doesn't use demangling")
+endif()
+
 if (NOT LIBCXXABI_ENABLE_SHARED AND NOT LIBCXXABI_ENABLE_STATIC)
   message(FATAL_ERROR "libc++abi must be built as either a shared or static library.")
 endif()
diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
index 4198827203fc..2b77f0b24874 100644
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -3,7 +3,6 @@ set(LIBCXXABI_SOURCES
   # C++ABI files
   cxa_aux_runtime.cpp
   cxa_default_handlers.cpp
-  cxa_demangle.cpp
   cxa_exception_storage.cpp
   cxa_guard.cpp
   cxa_handlers.cpp
@@ -19,6 +18,12 @@ set(LIBCXXABI_SOURCES
   private_typeinfo.cpp
 )
 
+if (NOT LIBCXXABI_STATIC_DEMANGLE_LIBRARY)
+  list(APPEND LIBCXXABI_SOURCES
+    cxa_demangle.cpp
+  )
+endif()
+
 if (LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS)
   list(APPEND LIBCXXABI_SOURCES
     stdlib_new_delete.cpp
@@ -154,6 +159,24 @@ endif()
 
 include(WarningFlags)
 
+if (LIBCXXABI_STATIC_DEMANGLE_LIBRARY)
+  add_library(cxxabi_demangle_static STATIC abort_message.cpp cxa_demangle.cpp ${LIBCXXABI_HEADERS})
+  target_link_libraries(cxxabi_demangle_static PRIVATE cxx-headers cxxabi-headers)
+  set_target_properties(cxxabi_demangle_static
+    PROPERTIES
+      CXX_EXTENSIONS OFF
+      CXX_STANDARD 20
+      CXX_STANDARD_REQUIRED OFF
+      COMPILE_FLAGS "${LIBCXXABI_COMPILE_FLAGS}"
+      LINK_FLAGS "${LIBCXXABI_LINK_FLAGS}"
+      OUTPUT_NAME "${LIBCXXABI_DEMANGLE_STATIC_OUTPUT_NAME}"
+    )
+  list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_demangle_static")
+  if (LIBCXXABI_INSTALL_STATIC_LIBRARY)
+    list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_demangle_static")
+  endif()
+endif()
+
 # Build the shared library.
 add_library(cxxabi_shared_objects OBJECT EXCLUDE_FROM_ALL ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
 cxx_add_warning_flags(cxxabi_shared_objects ${LIBCXXABI_ENABLE_WERROR} ${LIBCXXABI_ENABLE_PEDANTIC})
-- 
2.44.0.769.g3c40516874-goog