Warning, /frameworks/extra-cmake-modules/modules/CheckAtomic.cmake is written in an unsupported language. File is not indexed.

 # SPDX-FileCopyrightText: 2003-2018 University of Illinois at Urbana-Champaign.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
 #[=======================================================================[.rst:
 CheckAtomic
 -----------
 
 Check if the compiler supports std:atomic out of the box or if libatomic is
 needed for atomic support. If it is needed libatomicis added to
 ``CMAKE_REQUIRED_LIBRARIES``. So after running CheckAtomic you can use
 std:atomic.
 
 Since 5.75.0.
 #]=======================================================================]
 
 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>
   std::atomic<int> x;
   std::atomic<short> y;
   std::atomic<char> z;
   int main() {
     ++z;
     ++y;
     return ++x;
   }
   " ${varname})
   set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
 endfunction()
 
 function(check_working_cxx_atomics64 varname)
   set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
   set(CMAKE_REQUIRED_FLAGS "-std=c++11 ${CMAKE_REQUIRED_FLAGS}")
   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})
   set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
 endfunction()
 
 # Check for (non-64-bit) atomic operations.
 if(MSVC)
   set(HAVE_CXX_ATOMICS_WITHOUT_LIB True)
 elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE)
   # 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)
       list(APPEND 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()
     else()
       message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
     endif()
   endif()
 endif()
 
 # Check for 64 bit atomic operations.
 if(MSVC)
   set(HAVE_CXX_ATOMICS64_WITHOUT_LIB True)
 elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE)
   # First check if atomics work without the library.
   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)
       list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
       check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB)
       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()