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b072c44c08
Sometimes linking against libatomic is required for atomic ops, if the platform doesn't support lock-free atomics. This is a fixup for #4556, which does not work as intended.
53 lines
1.7 KiB
CMake
53 lines
1.7 KiB
CMake
include(CheckCXXSourceCompiles)
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include(CheckLibraryExists)
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# Sometimes linking against libatomic is required for atomic ops, if
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# the platform doesn't support lock-free atomics.
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function(check_working_cxx_atomics varname)
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set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
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set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
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check_cxx_source_compiles("
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#include <atomic>
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#include <cstdint>
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std::atomic<uint64_t> x (0);
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int main() {
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uint64_t i = x.load(std::memory_order_relaxed);
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(void)i;
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return 0;
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}
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" ${varname})
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set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
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endfunction(check_working_cxx_atomics)
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if(NOT DEFINED COMPILER_IS_GCC_COMPATIBLE)
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if(MSVC OR APPLE)
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set(COMPILER_IS_GCC_COMPATIBLE OFF)
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else()
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set(COMPILER_IS_GCC_COMPATIBLE ON)
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endif()
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endif()
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if(NOT COMPILER_IS_GCC_COMPATIBLE)
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set(HAVE_ATOMICS_WITHOUT_LIB ON)
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else()
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# Check for 64 bit atomic operations.
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# First check if atomics work without the library.
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check_working_cxx_atomics(HAVE_ATOMICS_WITHOUT_LIB)
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# If not, check if the library exists, and atomics work with it.
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if(NOT HAVE_ATOMICS_WITHOUT_LIB)
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check_library_exists(atomic __atomic_load_8 "" HAVE_LIBATOMICS)
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mark_as_advanced(HAVE_LIBATOMICS)
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if(NOT HAVE_LIBATOMICS)
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message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
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endif()
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list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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check_working_cxx_atomics(HAVE_ATOMICS_WITH_LIB)
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if(NOT HAVE_ATOMICS_WITH_LIB)
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message(FATAL_ERROR "Host compiler must support std::atomic!")
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endif()
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list(APPEND CMAKE_C_STANDARD_LIBRARIES "-latomic")
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list(APPEND CMAKE_CXX_STANDARD_LIBRARIES "-latomic")
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endif()
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endif()
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