[Bug sanitizer/108628] New: ASAN at -O3 misses a stack-use-after-return

["shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108628

            Bug ID: 108628
           Summary: ASAN at -O3 misses a stack-use-after-return
           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 missed the stack-use-after-return, while
other opt levels detected it.

Clang at all opt levels can detect it.

Compiler explorer: https://godbolt.org/z/q5ezG1MK3

% cat a.c
int *a;
int **b = &a;
char c;
int d, g;
void h(int i) {
  long e[112];
  e;
  int *f = &i;
  a = f;
}
void j() {
  char *k[12];
  for (; d; d++)
    k[g] = &c;
}
int main() {
  j();
  h(-1);
  __builtin_printf("**b=%d\n", **b);
}
%
% gcc-tk -fsanitize=address -O3 a.c && ./a.out
**b=-1
%
% gcc-tk -fsanitize=address -O2 a.c && ./a.out
=================================================================
==1==ERROR: AddressSanitizer: stack-use-after-return on address 0x7f0646b00020
at pc 0x000000401148 bp 0x7ffed3f9a190 sp 0x7ffed3f9a188
READ of size 4 at 0x7f0646b00020 thread T0
    #0 0x401147 in main /a.c:19
    #1 0x7f064954c082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId:
1878e6b475720c7c51969e69ab2d276fae6d1dee)
    #2 0x4011ad in _start (/output.s+0x4011ad) (BuildId:
7b9e8ee9f7af16e4a0a8a05fef54777844619617)

Address 0x7f0646b00020 is located in stack of thread T0 at offset 32 in frame
    #0 0x40127f in h /a.c:5

  This frame has 1 object(s):
    [32, 36) 'i' (line 5) <== Memory access at offset 32 is inside this
variable
HINT: this may be a false positive if your program uses some custom stack
unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-use-after-return /a.c:19 in main
Shadow bytes around the buggy address:
  0x7f0646affd80: 00 00 00 00 00 00
...
%