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include(CheckCXXSourceCompiles)
include(CheckLibraryExists)
# Sometimes linking against libatomic is required for atomic ops, if
# the platform doesn't support lock-free atomics.
function(check_working_cxx_atomics varname)
set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
check_cxx_source_compiles("
#include <atomic>
#include <cstdint>
std::atomic<int> x1;
std::atomic<short> x2;
std::atomic<char> x3;
std::atomic<uint64_t> x (0);
int main() {
uint64_t i = x.load(std::memory_order_relaxed);
(void)i;
++x3;
++x2;
return ++x1;
}
" ${varname})
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_working_cxx_atomics)
if(NOT DEFINED COMPILER_IS_GCC_COMPATIBLE)
if(MSVC OR APPLE)
set(COMPILER_IS_GCC_COMPATIBLE OFF)
else()
set(COMPILER_IS_GCC_COMPATIBLE ON)
endif()
endif()
if(NOT COMPILER_IS_GCC_COMPATIBLE)
set(HAVE_ATOMICS_WITHOUT_LIB ON)
else()
# Check for 64 bit atomic operations.
# First check if atomics work without the library.
check_working_cxx_atomics(HAVE_ATOMICS_WITHOUT_LIB)
# If not, check if the library exists, and atomics work with it.
if(NOT HAVE_ATOMICS_WITHOUT_LIB)
check_library_exists(atomic __atomic_load_8 "" HAVE_LIBATOMICS)
mark_as_advanced(HAVE_LIBATOMICS)
if(NOT HAVE_LIBATOMICS)
message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
endif()
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
check_working_cxx_atomics(HAVE_ATOMICS_WITH_LIB)
if(NOT HAVE_ATOMICS_WITH_LIB)
message(FATAL_ERROR "Host compiler must support std::atomic!")
endif()
list(APPEND CMAKE_C_STANDARD_LIBRARIES "-latomic")
list(APPEND CMAKE_CXX_STANDARD_LIBRARIES "-latomic")
endif()
endif()
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