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#
# Copyright 2020 Kenneth Haase <kh@beingmeta.com>
#
# This software is supplied under the terms of the MIT License, a
# copy of which should be located in the distribution where this
# file was obtained (LICENSE.txt). A copy of the license may also be
# found online at https://opensource.org/licenses/MIT.
#
# atomic builtins are required for threading support.
INCLUDE(CheckIncludeFiles)
INCLUDE(CheckCSourceCompiles)
INCLUDE(CheckLibraryExists)
# Sometimes linking against libatomic is required for atomic ops, if
# the platform doesn't support lock-free atomics.
function(check_c_atomics_without_lib varname)
CHECK_C_SOURCE_COMPILES("
#include <stdatomic.h>
int main() {
_Atomic long long x;
atomic_store(&x,3);
long long y = atomic_load(&x);
atomic_fetch_add(&x,12);
long long z = atomic_load(&x);
return x;
}
" ${varname})
endfunction(check_c_atomics_without_lib)
function(check_c_atomics_with_lib varname)
SET(SAVED_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
CHECK_C_SOURCE_COMPILES("
#include <stdatomic.h>
int main() {
_Atomic long long x;
atomic_store(&x,3);
long long y = atomic_load(&x);
atomic_fetch_add(&x,12);
long long z = atomic_load(&x);
return x;
}
" ${varname})
SET(CMAKE_REQUIRED_LIBRARIES "${SAVED_CMAKE_REQUIRED_LIBRARIES}")
endfunction(check_c_atomics_with_lib)
macro (CheckAtomicLib)
# First check if atomics work without the library.
if(MSVC)
set(HAVE_C_ATOMICS_WITHOUT_LIB True)
else()
check_c_atomics_without_lib(HAVE_C_ATOMICS_WITHOUT_LIB)
if(NOT HAVE_C_ATOMICS_WITHOUT_LIB)
check_library_exists(atomic __atomic_fetch_add_8 "" HAVE_LIBATOMIC)
if( HAVE_LIBATOMIC )
check_c_atomics_with_lib(HAVE_C_ATOMICS_WITH_LIB)
if (NOT HAVE_C_ATOMICS_WITH_LIB)
message(FATAL_ERROR "Host compiler must support atomic types!")
endif()
else()
message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
endif()
endif()
endif()
endmacro (CheckAtomicLib)
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