https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109099
--- Comment #3 from urbanjost at comcast dot net --- So I think you are right and this is not standard; so instead of an error at most it would be nice to get a warning/error message indicating too many values were used or that an extension is used when the -std flag is used. If preferable this can be closed; but it would be nice to get a warning/error like NAG. For backward compatibility I think just a warning is fine myself.
