[Bug sanitizer/108497] New: UBsan at -O1 failed to report an integer-overflow

[Bug sanitizer/108497] New: UBsan at -O1 failed to report an integer-overflow

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108497

            Bug ID: 108497
           Summary: UBsan at -O1 failed to report an integer-overflow
           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, UBsan `-fsanitize=undefined -fno-sanitize-recover=all
-O1` failed to report the integer-overflow, while other opt levels reported it.
Interestingly, if you don't specify `-fno-sanitize-recover=all`, UBSAN can
report it normally.

Clang at all opt levels can detect it.

Compiler explorer: https://godbolt.org/z/dE1sfcz5f

% cat a.c
int a, c;
long *b;
int main() {
  int d = 0, e = 0;
  for (; e < 2; e++)
  f:
    for (; a; a++)
      d % *b;
  d = d + 1228455618;
  c ^= 0 == 0;
  if (c) {
    e = 0;
    for (; e < 1; e++)
      ;
    goto f;
  }
}
%
% gcc-tk -O1 -fsanitize=undefined -fno-sanitize-recover=all a.c && ./a.out
%
% gcc-tk -O2 -fsanitize=undefined -fno-sanitize-recover=all a.c && ./a.out
/a.c:9:5: runtime error: signed integer overflow: 1228455618 + 1228455618
cannot be represented in type 'int'
%

[Bug sanitizer/108497] UBsan at -O1 failed to report an integer-overflow

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108497

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-01-23

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed.

[Bug sanitizer/108497] UBsan at -O1 failed to report an integer-overflow

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108497

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
@Jakub: Can you please take a look?

[Bug sanitizer/108497] UBsan at -O1 failed to report an integer-overflow

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108497

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Not now nor in the near future.  After all, it isn't a regression, so couldn't
be fixed during stage4 anyway.

[Bug sanitizer/108497] UBsan at -O1 failed to report an integer-overflow

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108497

--- Comment #4 from Li Shaohua <shaohua.li at inf dot ethz.ch> ---
(In reply to Jakub Jelinek from comment #3)
> Not now nor in the near future.  After all, it isn't a regression, so
> couldn't be fixed during stage4 anyway.

This bug affects GCC>=8. GCC<=7 work fine on this case.