[Bug tree-optimization/128075] New: wrong code at -O1 and above when a nested function returns the address of a local of its containing function

[kyuwoncho18 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128075

            Bug ID: 128075
           Summary: wrong code at -O1 and above when a nested function
                    returns the address of a local of its containing
                    function
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kyuwoncho18 at gmail dot com
  Target Milestone: ---
            Target: x86_64-pc-linux-gnu

int outer(void)
{
  int x = 1;
  __attribute__((noinline)) int *g(void) { return &x; }
  int *p = g();
  *p = 5;
  return x;
}

int main(void)
{
  if (outer() != 5)
    __builtin_abort();
}

godbolt: https://godbolt.org/z/voe9bKxf3

g returns &x, so *p = 5 sets x and outer must return 5. With -O0, or -O2
-fno-tree-sra, the program exits normally; with -O1, -O2, -O3 or -Os outer
returns 1 and the program aborts.