caio/clang-p2996
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[runtimes] Probe for -nostdlib++ and -nostdinc++ with the C compiler (#108357)

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While these flags semantically are relevant only for C++, we do add them
to CMAKE_REQUIRED_FLAGS if they are detected. All flags in that variable
are used both when testing compilation of C and C++ (and for detecting
libraries, which uses the C compiler driver).

Therefore, to be sure we safely can add the flags to
CMAKE_REQUIRED_FLAGS, test for the option with the C language.

This should fix compilation with GCC; newer versions of GCC do support
the -nostdlib++ option, but it's only supported by the C++ compiler
driver, not the C driver. (However, many builds of GCC also do accept
the option with the C driver, if GCC was compiled with Ada support
enabled, see [1]. That's why this issue isn't noticed in all
configurations with GCC.)

Clang does support these options in both C and C++ driver modes.

This should fix #90332.

[1]
https://github.com/llvm/llvm-project/issues/90332#issuecomment-2325099254
This commit is contained in:
Martin Storsjö
2024-10-24 23:46:04 +03:00
committed by GitHub
parent a14a83d9a1
commit 75d0281bc8
6 changed files with 35 additions and 19 deletions
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12
libunwind/cmake/config-ix.cmake
View File

@@ -34,9 +34,13 @@ endif()
# required during compilation (which has the -nostdlib++ or -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
#
# Adding flags to CMAKE_REQUIRED_FLAGS will include the flags both when testing
# compilation of C and C++. Therefore test to make sure that the flags are
# supported by the C compiler driver, before deciding to include them.
llvm_check_compiler_linker_flag(CXX "-nostdlib++" CXX_SUPPORTS_NOSTDLIBXX_FLAG)
if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
llvm_check_compiler_linker_flag(C "-nostdlib++" C_SUPPORTS_NOSTDLIBXX_FLAG)
if (C_SUPPORTS_NOSTDLIBXX_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
else()
llvm_check_compiler_linker_flag(C "-nodefaultlibs" C_SUPPORTS_NODEFAULTLIBS_FLAG)
@@ -47,7 +51,7 @@ endif()
# Only link against compiler-rt manually if we use -nodefaultlibs, since
# otherwise the compiler will do the right thing on its own.
if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (NOT C_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBUNWIND_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
@@ -82,7 +86,7 @@ if (NOT CXX_SUPPORTS_NOSTDLIBXX_FLAG AND C_SUPPORTS_NODEFAULTLIBS_FLAG)
endif()
endif()
if (CXX_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (C_SUPPORTS_NOSTDLIBXX_FLAG OR C_SUPPORTS_NODEFAULTLIBS_FLAG)
if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
endif ()

2
libunwind/src/CMakeLists.txt
View File

@@ -66,7 +66,7 @@ set(LIBUNWIND_SOURCES
${LIBUNWIND_ASM_SOURCES})
# Generate library list.
if (CXX_SUPPORTS_NOSTDLIBXX_FLAG)
if (C_SUPPORTS_NOSTDLIBXX_FLAG)
add_link_flags_if_supported(-nostdlib++)
else()
if (LIBUNWIND_USE_COMPILER_RT)