[PATCH] D15440: [libc++abi] Use libgcc and libgcc_s to provide _Unwind symbols instead of libgcc_eh.a

[Eric Fiselier via cfe-commits]

EricWF created this revision.
EricWF added reviewers: danalbert, chandlerc, mclow.lists, compnerd, ismail.
EricWF added a subscriber: cfe-commits.

libgcc_eh.a cannot be used when building libc++abi as a shared library (the default configuration). See this post for some more discussion: https://gcc.gnu.org/ml/gcc/2012-03/msg00104.html

This patch reverts back to using libgcc_s when linking libc++abi.so. However gcc_s doesn't contain all of the symbols needed by libc++abi.so. The missing symbols will be resolved by libgcc.a when linking the final executable.



http://reviews.llvm.org/D15440

Files:
  cmake/config-ix.cmake
  src/CMakeLists.txt

Index: src/CMakeLists.txt
===================================================================
--- src/CMakeLists.txt
+++ src/CMakeLists.txt
@@ -19,6 +19,23 @@
   typeinfo.cpp
 )
 
+
+# Remove a list of flags from all CMake variables that affect compile flags.
+# This can be used to remove unwanted flags specified on the command line
+# or added in other parts of LLVM's cmake configuration.
+macro(remove_flags)
+  foreach(var ${ARGN})
+    string(REPLACE "${var}" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+    string(REPLACE "${var}" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+    string(REPLACE "${var}" "" CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
+    string(REPLACE "${var}" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+    string(REPLACE "${var}" "" CMAKE_SHARED_MODULE_FLAGS "${CMAKE_SHARED_MODULE_FLAGS}")
+    remove_definitions(${var})
+  endforeach()
+endmacro(remove_flags)
+
+remove_flags(-Wl,-z,defs)
+
 if (UNIX AND NOT (APPLE OR CYGWIN))
   list(APPEND LIBCXXABI_SOURCES cxa_thread_atexit.cpp)
 endif()
@@ -40,17 +57,25 @@
   add_definitions(-DHAVE___CXA_THREAD_ATEXIT_IMPL)
 endif()
 
-# Generate library list.
+# Generate library list. When not using LLVM unwinder libgcc_s should be the
+# first and last library on the link line. This behavior mimics clang's
+# behavior.
 set(libraries ${LIBCXXABI_CXX_ABI_LIBRARIES})
-append_if(libraries LIBCXXABI_HAS_C_LIB c)
+
+if (NOT LIBCXXABI_USE_LLVM_UNWINDER)
+  append_if(libraries LIBCXXABI_HAS_GCC_S_LIB gcc_s)
+endif()
+
 if (LIBCXXABI_ENABLE_THREADS)
   append_if(libraries LIBCXXABI_HAS_PTHREAD_LIB pthread)
 endif()
 
+append_if(libraries LIBCXXABI_HAS_C_LIB c)
+
 if (LIBCXXABI_USE_LLVM_UNWINDER)
   list(APPEND libraries unwind)
 else()
-  append_if(libraries LIBCXXABI_HAS_GCC_EH_LIB gcc_eh)
+  append_if(libraries LIBCXXABI_HAS_GCC_S_LIB gcc_s)
 endif()
 
 # Setup flags.
Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -42,6 +42,6 @@
 check_library_exists(c fopen "" LIBCXXABI_HAS_C_LIB)
 check_library_exists(dl dladdr "" LIBCXXABI_HAS_DL_LIB)
 check_library_exists(pthread pthread_once "" LIBCXXABI_HAS_PTHREAD_LIB)
-check_library_exists(gcc_eh _Unwind_GetRegionStart "" LIBCXXABI_HAS_GCC_EH_LIB)
+check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXXABI_HAS_GCC_S_LIB)
 check_library_exists(c __cxa_thread_atexit_impl ""
   LIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL)


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