https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107866
Bug ID: 107866 Summary: gcc trunk's UBSan misses a Nll-pointer-dereference at -O3. Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: sanitizer Assignee: unassigned at gcc dot gnu.org Reporter: shaohua.li at inf dot ethz.ch CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org, jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at gcc dot gnu.org Target Milestone: --- For the following code, `gcc-trunk -O3 -fsanitize=undefined` misses the NULL-pointer-dereference, while `gcc-trunk -Ox -fsanitize=address` (x=0,1, 2, s) can detect it. gcc-12 has the same issue. gcc-11 can detect the bug at all optimization levels. clang can also detect it at all optimization levels. Compiler explorer: https://godbolt.org/z/WhrzP6zdf % cat a.c int *a; void main() { for (;;) { a = 0; if (*a) break; } } % % gcc-tk -O3 -fsanitize=undefined -fno-sanitize-recover=all a.c &&./a.out Segmentation fault % gcc-tk -O2 -fsanitize=undefined -fno-sanitize-recover=all a.c &&./a.out a.c:5:9: runtime error: load of null pointer of type 'int' %