https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53232
--- Comment #11 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- (In reply to Vincent Lefèvre from comment #8) > (In reply to comment #6) > > Er, if you want to find portability problems for people not using C99 then > > don't use -std=c99. Then -Wreturn-type warns about main. > > There are several reasons one may want to use -std=c99, e.g. to be able to > use C99 features when available (via autoconf and/or preprocessor tests). In any case, there does not seem to be a -std value to say that the program must be valid for all C90, C99, C11 and C17 standards (and the future C23 standard). That's what portability is about.