https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109031
--- Comment #27 from Martin Liška <marxin at gcc dot gnu.org> --- Polished a bit more into: unsigned char f = 0; int main() { unsigned g = 0; unsigned *p1 = &g; unsigned char *p2 = &f; do { (*p1)++; (*p2)--; } while (f); __builtin_printf ("g=%u\n", g); if (g != 256) __builtin_abort(); return 0; }