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[libc++] Use -nostdlib++ on GCC unconditionally #68832

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merged 4 commits into from
Oct 13, 2023
Merged

[libc++] Use -nostdlib++ on GCC unconditionally #68832

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9ca88d1
[libc++] Use -nostdlib++ on GCC unconditionally
ldionne Oct 11, 2023
44a694e
Merge branch 'main' into review/cmake-nostdlibxx
ldionne Oct 12, 2023
db65842
Fix typo on Windows and use -nostdlib++ in the benchmarks
ldionne Oct 12, 2023
be714f7
Remove broken options on MSVC.
ldionne Oct 13, 2023
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32 changes: 2 additions & 30 deletions libcxx/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -642,18 +642,8 @@ get_sanitizer_flags(SANITIZER_FLAGS "${LLVM_USE_SANITIZER}")

# Link system libraries =======================================================
function(cxx_link_system_libraries target)

# In order to remove just libc++ from the link step
# we need to use -nostdlib++ whenever it is supported.
# Unfortunately this cannot be used universally because for example g++ supports
# only -nodefaultlibs in which case all libraries will be removed and
# all libraries but c++ have to be added in manually.
if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
target_add_link_flags_if_supported(${target} PRIVATE "-nostdlib++")
else()
target_add_link_flags_if_supported(${target} PRIVATE "-nodefaultlibs")
target_add_compile_flags_if_supported(${target} PRIVATE "/Zl")
target_add_link_flags_if_supported(${target} PRIVATE "/nodefaultlib")
if (NOT MSVC)
target_link_libraries(${target} PRIVATE "-nostdlib++")
endif()

if (CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG AND LIBCXXABI_USE_LLVM_UNWINDER)
Expand All @@ -663,24 +653,6 @@ function(cxx_link_system_libraries target)
target_add_link_flags_if_supported(${target} PRIVATE "--unwindlib=none")
endif()

if (NOT APPLE) # On Apple platforms, we always use -nostdlib++ so we don't need to re-add other libraries
if (LIBCXX_HAS_PTHREAD_LIB)
target_link_libraries(${target} PRIVATE pthread)
endif()

if (LIBCXX_HAS_C_LIB)
target_link_libraries(${target} PRIVATE c)
endif()

if (LIBCXX_HAS_M_LIB)
target_link_libraries(${target} PRIVATE m)
endif()

if (LIBCXX_HAS_RT_LIB)
target_link_libraries(${target} PRIVATE rt)
endif()
endif()

if (LIBCXX_USE_COMPILER_RT)
find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY)
if (LIBCXX_BUILTINS_LIBRARY)
Expand Down
2 changes: 1 addition & 1 deletion libcxx/benchmarks/CMakeLists.txt
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Expand Up @@ -122,7 +122,7 @@ endif()
add_library( cxx-benchmarks-flags-libcxx INTERFACE)
target_link_libraries( cxx-benchmarks-flags-libcxx INTERFACE cxx-benchmarks-flags)
target_compile_options(cxx-benchmarks-flags-libcxx INTERFACE ${SANITIZER_FLAGS} -Wno-user-defined-literals -Wno-suggest-override)
target_link_options( cxx-benchmarks-flags-libcxx INTERFACE -nodefaultlibs "-L${BENCHMARK_LIBCXX_INSTALL}/lib" "-L${BENCHMARK_LIBCXX_INSTALL}/lib64" ${SANITIZER_FLAGS})
target_link_options( cxx-benchmarks-flags-libcxx INTERFACE -nostdlib++ "-L${BENCHMARK_LIBCXX_INSTALL}/lib" "-L${BENCHMARK_LIBCXX_INSTALL}/lib64" ${SANITIZER_FLAGS})

set(libcxx_benchmark_targets)

Expand Down
15 changes: 0 additions & 15 deletions libcxx/cmake/config-ix.cmake
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Expand Up @@ -14,14 +14,6 @@ include(CheckCSourceCompiles)
# link with --uwnindlib=none. Check if that option works.
llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_EQ_NONE_FLAG)

if(WIN32 AND NOT MINGW)
# NOTE(compnerd) this is technically a lie, there is msvcrt, but for now, lets
# let the default linking take care of that.
set(LIBCXX_HAS_C_LIB NO)
else()
check_library_exists(c fopen "" LIBCXX_HAS_C_LIB)
endif()

if (NOT LIBCXX_USE_COMPILER_RT)
if(WIN32 AND NOT MINGW)
set(LIBCXX_HAS_GCC_S_LIB NO)
Expand Down Expand Up @@ -54,9 +46,6 @@ else()
endif()

if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXX_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
if (LIBCXX_USE_COMPILER_RT)
include(HandleCompilerRT)
find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY
Expand Down Expand Up @@ -108,22 +97,18 @@ if(WIN32 AND NOT MINGW)
# TODO(compnerd) do we want to support an emulation layer that allows for the
# use of pthread-win32 or similar libraries to emulate pthreads on Windows?
set(LIBCXX_HAS_PTHREAD_LIB NO)
set(LIBCXX_HAS_M_LIB NO)
set(LIBCXX_HAS_RT_LIB NO)
set(LIBCXX_HAS_ATOMIC_LIB NO)
elseif(APPLE)
set(LIBCXX_HAS_PTHREAD_LIB NO)
set(LIBCXX_HAS_M_LIB NO)
set(LIBCXX_HAS_RT_LIB NO)
set(LIBCXX_HAS_ATOMIC_LIB NO)
elseif(FUCHSIA)
set(LIBCXX_HAS_M_LIB NO)
set(LIBCXX_HAS_PTHREAD_LIB NO)
set(LIBCXX_HAS_RT_LIB NO)
check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
else()
check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB)
check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
endif()