[Bug tree-optimization/103961] [12 Regression] gcc-12 apparently miscompiles libcap's cap_to_text() function since r12-6030-g422f9eb7011b76c1

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103961

--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Testcase with nicer formatting:

extern inline __attribute__ ((__gnu_inline__)) int
sprintf (char *restrict s, const char *restrict fmt, ...)
{
  return __builtin___sprintf_chk (s, 1, __builtin_object_size (s, 2 > 1),
                                  fmt, __builtin_va_arg_pack ());
}

void
cap_to_text (int c)
{
  char buf[1572];
  char *p;
  int n, t;
  p = 20 + buf;
  for (t = 8; t--; )
    {
      for (n = 0; n < c; n++)
        p += sprintf (p, "a,");
      p--;
      sprintf (p, "+");
    }
}

Indeed, early_objsz already inserts the bogus:
  p_16 = p_3 + 18446744073709551615;
  _17 = __builtin_object_size (p_16, 1);
  _24 = MIN_EXPR <_17, 0>;
  _25 = __builtin___sprintf_chk (p_16, 1, _24, "+");