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

[marxin at gcc dot gnu.org]

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

--- Comment #12 from Martin Liška <marxin at gcc dot gnu.org> ---
Self-contained test-case:

extern __inline __attribute__((__gnu_inline__)) int sprintf(
    char *__restrict __s, const char *__restrict __fmt, ...) {
  return __builtin___sprintf_chk(__s, 2 - 1, __builtin_object_size(__s, 2 > 1),
                                 __fmt, __builtin_va_arg_pack());
}

int main() {
  char buf[16];
  char *p = buf;

  for (int t = 0; t < 1; t++) {
    for (int n = 0; n < 1; n++) p += sprintf(p, "a,");

    p--;
    sprintf(p, "+");
  }

  __builtin_printf("buf: %s\n", buf);
  if (buf[0] != 'a') __builtin_abort();

  return 0;
}