http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60121
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Chengnian Sun from comment #6) > The test case can be further reduced to the following code, which is NOT > dead or dependent on bug 60115. > > int b[1]; > int f() { > return b[9999]; > } Because we don't warn in the front-end. That was on purpose. I can find the old bug reports of why we don't want to warn in the front-end. The warning only happens in VPR which is only enabled for -O2 and above (-Os is -O2 plus optimize for size really).