cmake HAVE_C11_ATOMIC examples

Froser/gamemachine src/3rdparty/openal-soft-1.19.1/CMakeLists.txt :262 

CHECK_C_SOURCE_COMPILES(
"#include <stdatomic.h>
 int _Atomic foo = ATOMIC_VAR_INIT(0);
 int main()
 {
     atomic_fetch_add(&foo, 2);
     return 0;
 }"
HAVE_C11_ATOMIC)

valkey-io/valkey cmake/Modules/ValkeySetup.cmake :254 

check_include_files(stdatomic.h HAVE_C11_ATOMIC)

valkey-io/valkey cmake/Modules/ValkeySetup.cmake :367 

unset(HAVE_C11_ATOMIC CACHE)