[Bug sanitizer/108343] New: ASAN at -O3 misses a heap-use-after-free

[shaohua.li at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108343

            Bug ID: 108343
           Summary: ASAN at -O3 misses a heap-use-after-free
           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 misses the heap-use-after-free, while other
opt levels catch it.

% cat a.c
#include <stdlib.h>
int a, c;
char b;
int main() {
  char **d = malloc(sizeof(char*));
  for(int i=0; i<1; i++)
    *d = malloc(sizeof(char));
  d[0][0] = 0;
  int e, f = -1;
  free(d[0]);
  free(d);
  for (; a <= 1; a++) {
    long g[1];
    g;
    c = f;
    e = 0;
    for (; e <= 1; e++) {
      c |= d[a][0];
      if (b)
        c = a;
    }
  }
  return c;
}
%
% gcc-tk -fsanitize=address -g -O2 a.c && ./a.out
=================================================================
==2253130==ERROR: AddressSanitizer: heap-use-after-free on address
0x602000000010 at pc 0x000000401210 bp 0x7ffdd10f9a90 sp 0x7ffdd10f9a88
READ of size 8 at 0x602000000010 thread T0
    #0 0x40120f in main /zdata/shaoli/sanitizertesting/mutate/bugs/gcc/a.c:18
    #1 0x7f15496b0082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId:
1878e6b475720c7c51969e69ab2d276fae6d1dee)
...
%
% gcc-tk -fsanitize=address -g -O3 a.c && ./a.out
%