Merge topic 'apple_clang_cxx_20_support'

9523ca72e2 Features: Activate C++20 support for AppleClang 10.0+

Acked-by: Kitware Robot <[email protected]>
Merge-request: !3294

Help/release/dev/apple-clang-supports-cxx20.rst

@@ -0,0 +1,4 @@
+apple-clang-supports-cxx20
+--------------------------
+
+* AppleClang compiler have learned how to compile C++20.

Modules/Compiler/AppleClang-CXX.cmake

@@ -30,9 +30,13 @@ if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.1)
   set(CMAKE_CXX17_EXTENSION_COMPILE_OPTION "-std=gnu++1z")
 endif()
 
-
 if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 8.0)
     set(CMAKE_CXX11_STANDARD__HAS_FULL_SUPPORT ON)
 endif()
 
+if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10.0)
+  set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std=c++2a")
+  set(CMAKE_CXX20_EXTENSION_COMPILE_OPTION "-std=gnu++2a")
+endif()
+
 __compiler_check_default_language_standard(CXX 4.0 98)