https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85678 --- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> --- C89 6.7p4 looks equivalent to C99 6.9p5, so I don't see why -std=c89 should imply -fcommon. It's just as bad in C89 as in later standards.