https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66228
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Richard Biener from comment #1) > I think this is an effective duplicate of PR61886. With GCC 5 I get > > rguenther@murzim:/tmp> gcc-5 t.i -O -flto Right you need to either use -std=gnu90 or -fgnu89-inline for GCC 5+.