Require CMake 3.25 and add configure time validation for checking if given compiler CMake is processing with supports C++11 or C++14 standard in order to make sure DXC will be built correctly - throw an error if not. Check some of available CMake modules and decide to use try_compile for that because modules with simpler implementation of our check didn't work for some reason

Author: AnastaZIuk

3rdparty/dxc/CMakeLists.txt

@@ -37,15 +37,32 @@ set(SPIRV_SKIP_TESTS ON CACHE INTERNAL "Skip SPIRV-Tools tests")
 set(SPIRV_SKIP_EXECUTABLES ON CACHE INTERNAL "Skip SPIRV-Tools executable build")
 set(HLSL_ENABLE_DEBUG_ITERATORS ON CACHE BOOL "Enable Debug iterators" FORCE)
 
-set(CMAKE_CXX_STANDARD 11)
+nbl_adjust_flags()
+
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_STANDARD 11) # compiler must support exactly c++11 or c++14 standard in order to be able to build DXC libraries
 if(NBL_DYNAMIC_MSVC_RUNTIME)
 	set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>DLL")
 else()
 	set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")		
 endif()
 
-add_subdirectory(dxc dxc) # for dxcompiler target
+try_compile(DXC_COMPILE_TEST_PASSED
+	SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/test/test.cpp"
+	OUTPUT_VARIABLE DXC_COMPILE_RET_VAL
+	CXX_STANDARD ${CMAKE_CXX_STANDARD}
+	CXX_STANDARD_REQUIRED ON
+)
+
+if(DXC_COMPILE_TEST_PASSED)
+	set(DXC_COMPILE_TEST_DONE ON CACHE BOOL "")
+else()
+	message(FATAL_ERROR "${DXC_COMPILE_RET_VAL}")
+endif()
+
+add_subdirectory(dxc dxc)
 set(CMAKE_CXX_STANDARD 20) # it's mandatory
+unset(CMAKE_CXX_STANDARD_REQUIRED)
 
 include(FetchContent)
 set(FC_EXTERNAL_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/external")

3rdparty/dxc/test/test.cpp

@@ -2,7 +2,7 @@
 # This file is part of the "Nabla Engine".
 # For conditions of distribution and use, see copyright notice in nabla.h.in or nabla.h
 
-cmake_minimum_required(VERSION 3.20)
+cmake_minimum_required(VERSION 3.25)
 #policies
 cmake_policy(SET CMP0072 OLD) #not yet, would need to get pointers to all OpenGL functions
 set(OpenGL_GL_PREFERENCE LEGACY)