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[CMake] Add -Wl,-z,pack-relative-relocs if supported #208217

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[CMake] Add -Wl,-z,pack-relative-relocs if supported #208217

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19 changes: 19 additions & 0 deletions llvm/cmake/modules/HandleLLVMOptions.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -1153,6 +1153,25 @@ if (LLVM_USE_SPLIT_DWARF AND
endif()
endif()

# For PIC builds, enable RELR if supported by the linker and loader.
# glibc supports RELR since 2.36. musl supports RELR since 1.2.4, but there's
# no easy way to detect or feature-test this.
if (LLVM_ENABLE_PIC AND LLVM_USING_GLIBC)
CHECK_CXX_SOURCE_COMPILES("
#include <cstdio>
#if __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 36)
#error
#endif
int main() { return 0; }
" GLIBC_2_36_OR_NEWER)
if (GLIBC_2_36_OR_NEWER)
include(CheckLinkerFlag)
check_linker_flag(CXX "-Wl,-z,pack-relative-relocs" LINKER_SUPPORTS_RELR)
append_if(LINKER_SUPPORTS_RELR "-Wl,-z,pack-relative-relocs"
CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
endif()
endif()

add_compile_definitions(__STDC_CONSTANT_MACROS)
add_compile_definitions(__STDC_FORMAT_MACROS)
add_compile_definitions(__STDC_LIMIT_MACROS)
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