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#
# This file is mostly inspired by
# https://github.com/llvm-mirror/llvm/blob/master/cmake/modules/CheckAtomic.cmake
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
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)
CHECK_CXX_SOURCE_COMPILES("
#include <atomic>
std::atomic<int> x;
int main() {
return x;
}
" ${varname})
endfunction(CHECK_WORKING_CXX_ATOMICS)
function(CHECK_WORKING_CXX_ATOMICS64 varname)
CHECK_CXX_SOURCE_COMPILES("
#include <atomic>
#include <cstdint>
std::atomic<uint64_t> x (0);
int main() {
uint64_t i = x.load(std::memory_order_relaxed);
return 0;
}
" ${varname})
endfunction(CHECK_WORKING_CXX_ATOMICS64)
macro(CHECK_ATOMICS_LIB_REQUIRED required_var)
set(${required_var} FALSE)
if(MSVC)
set(${required_var} FALSE)
else()
# First check if atomics work without the library.
CHECK_WORKING_CXX_ATOMICS(HAVE_CXX_ATOMICS_WITHOUT_LIB)
# If not, check if the library exists, and atomics work with it.
if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
if(HAVE_LIBATOMIC)
set(${required_var} TRUE)
set(CMAKE_REQUIRED_LIBRARIES "atomic")
CHECK_WORKING_CXX_ATOMICS(HAVE_CXX_ATOMICS_WITH_LIB)
if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
message(FATAL_ERROR "Host compiler must support std::atomic!")
endif()
unset(CMAKE_REQUIRED_LIBRARIES)
else()
message(
FATAL_ERROR
"Host compiler appears to require libatomic, but cannot find it.")
endif()
endif()
# Same check, but for 64-bit atomics.
CHECK_WORKING_CXX_ATOMICS64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
# If not, check if the library exists, and atomics work with it.
if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64)
if(HAVE_CXX_LIBATOMICS64)
set(${required_var} TRUE)
set(CMAKE_REQUIRED_LIBRARIES "atomic")
CHECK_WORKING_CXX_ATOMICS64(HAVE_CXX_ATOMICS64_WITH_LIB)
unset(CMAKE_REQUIRED_LIBRARIES)
if (NOT HAVE_CXX_ATOMICS64_WITH_LIB)
message(FATAL_ERROR "Host compiler must support 64-bit std::atomic!")
endif()
else()
message(
FATAL_ERROR
"Host compiler appears to require libatomic for 64-bit operations, but cannot find it.")
endif()
endif()
endif()
endmacro(CHECK_ATOMICS_LIB_REQUIRED)
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