XL C/C++ helps protect your investment in your existing C/C++ source code by providing compiler invocation commands that instruct the compiler to compile your application code to a specific language level.
You can also use the -qlanglvl compiler option to specify a given language level, and the compiler will issue warnings, errors, and severe error messages if language or language extension elements in your program source do not conform to that language level.
See -qlanglvl for more information.