def METHOD_NAME() -> Optional[List[str]]:
    compiler = cmake_cache_var("CMAKE_C_COMPILER")  # could do CXX too
    if compiler is None:
        print("Couldn't find the compiler, os defines will be omitted...")
        return None
    import tempfile
    temp_c = tempfile.mkstemp(suffix=".c")[1]
    temp_def = tempfile.mkstemp(suffix=".def")[1]
    os.system("%s -dM -E %s > %s" % (compiler, temp_c, temp_def))
    temp_def_file = open(temp_def)
    lines = [l.strip() for l in temp_def_file if l.strip()]
    temp_def_file.close()
    os.remove(temp_c)
    os.remove(temp_def)
    return lines