[Bug sanitizer/109330] New: ASAN since GCC-9 missed a stack-use-after-scope at -O3

[Bug sanitizer/109330] New: ASAN since GCC-9 missed a stack-use-after-scope at -O3

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109330

            Bug ID: 109330
           Summary: ASAN since GCC-9 missed a stack-use-after-scope 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, ASAN at -O3 since GCC-9 missed the use-after-scope.
I checked the code and found that `*f=*g` and `return *f` were not optimized
away by the compiler.

Compiler explorer: https://godbolt.org/z/c96a6jWrY

% cat a.c
int a, c, d;
char b, e;
int main() {
  int *f = &a, *g = &c;
h:
  &g;
  for (; 0;)
    goto h;
  d = 0;
  for (; d <= 3; d++) {
    int i = *f;
    b && (e = 1);
    f = &i;
  }
  *f = *g;
  return *f;
}
% gcc-tk -O3 -fsanitize=address a.c && ./a.out
%
% gcc-8 -O3 -fsanitize=address a.c && ./a.out
================================================================
==1==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffd6b6b94d0
at pc 0x0000004008e1 bp 0x7ffd6b6b94a0 sp 0x7ffd6b6b9498
WRITE of size 4 at 0x7ffd6b6b94d0 thread T0
    #0 0x4008e0 in main /a.c:15
...
%

[Bug sanitizer/109330] ASAN since GCC-9 missed a stack-use-after-scope at -O3

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109330

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
We completely eliminate usage of 'f' with -O3 and thus there's no ASAN report.
Note, clang does not emit an error even with -O2.