From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id A5ABA3858D39; Mon, 24 Apr 2023 20:30:52 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A5ABA3858D39
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1682368252;
	bh=7gOs8Kn8tm/oPJtuU6CpN0rMVNfIljxncNb5wfGSkSo=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=rhX0Cv63q+sLYy3SZKk8MZg10ChoDYD/mou1p1ND/OXoxDq733KuD4u/j5GGHTH2l
	 RbwxdpNDPSOdXpEvuY1JKjkjYtJFKUdLm+/a1VIoNRE8c92pAgSBWwcAB2wT8Kctw0
	 iK4HgMwHmNF4dhCcKzFagsdWeaKA0S6YX19wYaQ0=
From: "gburca-gnu at ebixio dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/109609] [12/13/14 Regression] tail call for function
 even when passing a ptr which references a local array still
Date: Mon, 24 Apr 2023 20:30:52 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 12.2.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: gburca-gnu at ebixio dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.3
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-109609-4-08w1sSqn6d@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-109609-4@http.gcc.gnu.org/bugzilla/>
References: <bug-109609-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109609

--- Comment #7 from Gabriel Burca <gburca-gnu at ebixio dot com> ---
Here's the code that still fails with -O3 -fno-optimize-sibling-calls:

```
#include <string.h>
#include <stdint.h>
#define N 23
#define MAX_LEN 13
char dst[N + 1];

void stringify(uint64_t id) {
  char buf[MAX_LEN];
  char *ptr =3D buf + sizeof(buf);  // start from the end of buf
  *(--ptr) =3D '\0';                // terminate string
  while (id && ptr > buf) {
    *(--ptr) =3D static_cast<char>(id % 10) + '0';
    id /=3D 10;
  }
  __builtin_strncpy(dst, ptr, N);           // copy ptr/buf to dst
}

int main() {
  stringify(12345);
  if (strcmp(dst, "12345"))
    __builtin_abort();
}
```

Notably this only fails with -O3, not with -O2=