include_guard(GLOBAL) include(CheckCXXCompilerFlag) macro (APPEND_OPTION_IF_AVAILABLE _FLAG _LIST) string(MAKE_C_IDENTIFIER "CXX_FLAG_${_FLAG}" _VAR) check_cxx_compiler_flag(${_FLAG} ${_VAR}) if (${${_VAR}}) list(APPEND ${_LIST} ${_FLAG}) endif () endmacro ()