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 C77DA385841D; Wed, 19 Jan 2022 20:34:29 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C77DA385841D
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/104069] -Werror=use-after-free false positive on
 elfutils-0.186
Date: Wed, 19 Jan 2022 20:34:29 +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: 12.0
X-Bugzilla-Keywords: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: msebor at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-104069-4-8kMMJB4cZu@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-104069-4@http.gcc.gnu.org/bugzilla/>
References: <bug-104069-4@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
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Wed, 19 Jan 2022 20:34:29 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104069

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #14)
> Removing the test for !size from the first conditional avoids the warning=
.=20
> I don't fully understand what the code tries to do but the following avoi=
ds
> it at -O2 (only):
>=20
> void *xrealloc (void *ptr, int size)
> {
>   if (!size)
>     size =3D 1;
>   void *ret =3D __builtin_realloc (ptr, size);
>   if (!ret)
>     ret =3D __builtin_realloc (ptr, 1);
>   if (!ret) {
>     ret =3D __builtin_realloc (ptr, size);
>     if (!ret)
>       ret =3D __builtin_realloc(ptr, 1);
>     if (!ret)
>       __builtin_abort ();
>   }
>   return ret;
> }

This is definitely not what the code meant to do.
If I do xrealloc (malloc (30), 1024 * 1024 * 1024) and it returns non-NULL,
it certainly shouldn't be that it under the hood called realloc (ptr, 1)
because
the first realloc failed.
If you add that if (!size) size =3D 1;, then I think what is meant is just
  void *ret =3D __builtin_realloc (ptr, size);
  if (!ret)
    {
      ret =3D __builtin_realloc (ptr, size);
      if (!ret)
        die (...);
    }
  return ret;=