Build with c++2y for windows clang

Author: azonenberg

CMakeLists.txt

@@ -100,12 +100,16 @@ set(DISABLE_PCH CACHE BOOL "Disable precompiled headers as this may break certai
 set(BUILD_TESTING CACHE BOOL "Build unit tests")
 
 # Build with C++ 17 on Linux for maximum compatibility with older system
-# but for Windows, enable C++ 26 to bypass a deprecation warning
+# but for Windows, enable C++ 20 to bypass a deprecation warning
 # (workaround for https://github.com/KhronosGroup/Vulkan-Hpp/issues/2034)
 # even though we do not yet use any C++ 20 features in our codebase
-# also catch2 now wants to build with c++26 on windows clang?
 if(WIN32)
-	set(CMAKE_CXX_STANDARD 26)
+	#clang wants c++2y for some catch2 stuff
+	if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND BUILD_TESTING)
+		add_compile_options(--std=c++2y)
+	else()
+		set(CMAKE_CXX_STANDARD 20)
+	endif()
 else()
 	set(CMAKE_CXX_STANDARD 17)
 endif()