qt-build-tools/6.5.1/_tools/cmake/share/cmake-3.17/Modules/Compiler/AppleClang-C.cmake

include(Compiler/Clang)
__compiler_clang(C)

if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.0)
  set(CMAKE_C90_STANDARD_COMPILE_OPTION "-std=c90")
  set(CMAKE_C90_EXTENSION_COMPILE_OPTION "-std=gnu90")
  set(CMAKE_C90_STANDARD__HAS_FULL_SUPPORT ON)

  set(CMAKE_C99_STANDARD_COMPILE_OPTION "-std=c99")
  set(CMAKE_C99_EXTENSION_COMPILE_OPTION "-std=gnu99")
  set(CMAKE_C99_STANDARD__HAS_FULL_SUPPORT ON)

  set(CMAKE_C11_STANDARD_COMPILE_OPTION "-std=c11")
  set(CMAKE_C11_EXTENSION_COMPILE_OPTION "-std=gnu11")
  set(CMAKE_C11_STANDARD__HAS_FULL_SUPPORT ON)
endif()

__compiler_check_default_language_standard(C 4.0 99)