Add Basic Checks For Clang Compiler

CMakeLists.txt

@@ -56,13 +56,18 @@ enable_language(ASM)
 set(CMAKE_INSTALL_DEFAULT_COMPONENT_NAME "core")
 
 set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
+include(clang_version_check)
 include(InstallSymlink)
 include(MacroEnsureOutOfSourceBuild)
 include(dsym)
 include(xcproj)
 include(architecture)
 include(create_symlink)
 
+set(CLANG_RECOMMENDED_MINIMUM_VERSION 11)
+clang_version_check(${CMAKE_C_COMPILER} c ${CLANG_RECOMMENDED_MINIMUM_VERSION})
+clang_version_check(${CMAKE_CXX_COMPILER} cpp ${CLANG_RECOMMENDED_MINIMUM_VERSION})
+
 MACRO_ENSURE_OUT_OF_SOURCE_BUILD()
 
 set(DARLING_TOP_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")

cmake/clang_version_check.cmake

@@ -0,0 +1,42 @@
+set(MANUALLY_SET_COMPILER_ERROR_MESSAGE 
+"If you already have a supported version of clang installed, you may need to \
+manually set CMAKE_C_COMPILER and CMAKE_CXX_COMPILER. Refer to the Darling docs \
+for more details."
+)
+
+macro(clang_version_check compiler source_type clang_minimum_version)
+    if (compiler STREQUAL "")
+        message(FATAL_ERROR "Unable to find a compatible compiler")
+    endif (compiler STREQUAL "")
+
+    file(WRITE "${CMAKE_BINARY_DIR}/clang_major.${source_type}"  "#include <stdio.h>\n" 
+    "#if !__clang__\n" "#error \"Not running on a clang compiler!\"\n" "#endif\n" "int main() { printf(\"%d\", __clang_major__); }")
+    execute_process(COMMAND "${compiler}" "${CMAKE_BINARY_DIR}/clang_major.${source_type}" "-o" "clang_${source_type}_major"
+    	RESULT_VARIABLE BUILD_CLANG_TEST_RESULT
+    	OUTPUT_VARIABLE BUILD_CLANG_TEST_OUTPUT
+		COMMAND_ECHO NONE
+    )
+
+    if (BUILD_CLANG_TEST_RESULT)
+    	message(FATAL_ERROR
+			"Failed to build ${CMAKE_BINARY_DIR}/clang_major.${source_type}\n"
+			"This could indicate that `${compiler}` is either not a clang compiler, "
+			"or the path does not exist. ${MANUALLY_SET_COMPILER_ERROR_MESSAGE}")
+    endif (BUILD_CLANG_TEST_RESULT)
+
+    execute_process(COMMAND "${CMAKE_BINARY_DIR}/clang_${source_type}_major"
+    	RESULT_VARIABLE CLANG_MAJOR_VERSION_RESULT
+    	OUTPUT_VARIABLE CLANG_MAJOR_VERSION_OUTPUT
+    )
+
+    if (CLANG_MAJOR_VERSION_RESULT)
+        # This should normally never fail...
+    	message(FATAL_ERROR "Failed to check clang major version")
+    endif (CLANG_MAJOR_VERSION_RESULT)
+
+    if ("${CLANG_MAJOR_VERSION_OUTPUT}" LESS ${clang_minimum_version})
+    	message(FATAL_ERROR
+    		"Your clang version (${CLANG_MAJOR_VERSION_OUTPUT}) is below the recommend supported version (${clang_minimum_version})\n"
+			"${MANUALLY_SET_COMPILER_ERROR_MESSAGE}")
+    endif ("${CLANG_MAJOR_VERSION_OUTPUT}" LESS ${clang_minimum_version})
+endmacro()