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 4F6113858418; Sun, 14 Nov 2021 14:57:40 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4F6113858418
From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/103233] Warning from system libraries in user code: CWE-476
 -Werror=analyzer-null-dereference
Date: Sun, 14 Nov 2021 14:57:40 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: unknown
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: redi at gcc dot gnu.org
X-Bugzilla-Status: WAITING
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_status cf_reconfirmed_on everconfirmed
Message-ID: <bug-103233-4-wXc6dUoAYW@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-103233-4@http.gcc.gnu.org/bugzilla/>
References: <bug-103233-4@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: Sun, 14 Nov 2021 14:57:40 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103233

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2021-11-14
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Alejandro Colomar from comment #0)
> There are two problems here:
>=20
> One is a dereference of a NULL pointer in the standard C++ library code
> (at least that's what -fanalyzer reports).

The analyzer doesn't support C++ properly yet, and is completely wrong here.
See below.



> Another is that I'm seeing the error while compiling user code (my librar=
y):
> <https://github.com/alejandro-colomar/libalx>

What error? Please provide the code to reproduce the problem, not just a UR=
L,
see https://gcc.gnu.org/bugs


>     |/usr/include/c++/11/bits/stl_vector.h:346:25:
>     |  346 |         return __n !=3D 0 ? _Tr::allocate(_M_impl, __n) :
> pointer();
>     |      |=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
> ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     |      |                         |
>     |      |                         (7) following 'false' branch...

This cannot happen. The length is this->size() + 1 and we already checked f=
or
overflow, so it is guaranteed to be a positive integer.


>            |......
>            |  127 |         return static_cast<_Tp*>(::operator new(__n *
> sizeof(_Tp)));
>            |      |=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>            |      |                                                |
>            |      |                                                (12)
> ...to here
>            |      |                                                (13) t=
his
> call could return NULL


This is nonsense, operator new(size_t) cannot return null.=