https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68971
--- Comment #10 from Paul Eggert <eggert at gnu dot org> --- Unfortunately, the patch for Bug#68120 does not seem to have addressed the problem here. For example, although the following code uses the new feature enabled by that patch: int f (void) { return (__builtin_mul_overflow (0x7fffffff, 0x7fffffff, (int *) 0) ? 2 : 0x7fffffff * 0x7fffffff); } I still get the following warning with GCC 6.3.1 20161221 (Red Hat 6.3.1-1) x86-64: t.c: In function âfâ: t.c:4:19: warning: integer overflow in expression [-Woverflow] : 0x7fffffff * 0x7fffffff); ^