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 66DDD38582A3; Sun, 18 Dec 2022 17:41:36 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 66DDD38582A3
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1671385296;
	bh=eRUq4PVbRP2pauDgz8g7VRwPHPyRZ9+QosZgN7cRZ8E=;
	h=From:To:Subject:Date:From;
	b=HBEqx6JRdpl4icCfxm9K1cHKBZXXp2Be4vdWYrqT797yT6/UJUTDltXovQWvhP198
	 gxVL+RHbskrx1d6eVnL1tZM+UUdmPPC3Vue+woNU492xwcDHk/9F3VuZb3VN2SW08S
	 lv1TqwA3KHKSBCHkKBUuh4F9ctJhNgjWm6U/9eSI=
From: "romain.geissler at amadeus dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/108165] New: -Wdangling-reference false positive
Date: Sun, 18 Dec 2022 17:41:36 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: romain.geissler at amadeus dot com
X-Bugzilla-Status: UNCONFIRMED
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_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-108165-4@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=3D108165

            Bug ID: 108165
           Summary: -Wdangling-reference false positive
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: romain.geissler at amadeus dot com
  Target Milestone: ---

Hi,

The following snippet issues a wrong -Wdangling-reference warning when comp=
iled
with -Wall with current gcc trunk:

<<END_OF_FILE
struct A {};

struct B
{
    B(int) {}
};

const A& f(const A& a, const B&) {
    return a;
}

const A& g(const A& a) {
    const A& result =3D f(a, 42);

    return result;
}
END_OF_FILE

The warning is:

<source>: In function 'const A& g(const A&)':
<source>:13:14: warning: possibly dangling reference to a temporary
[-Wdangling-reference]
   13 |     const A& result =3D f(a, 42);
      |              ^~~~~~
<source>:13:24: note: the temporary was destroyed at the end of the full
expression 'f((* & a), B(42))'
   13 |     const A& result =3D f(a, 42);
      |                       ~^~~~~~~
ASM generation compiler returned: 0
<source>: In function 'const A& g(const A&)':
<source>:13:14: warning: possibly dangling reference to a temporary
[-Wdangling-reference]
   13 |     const A& result =3D f(a, 42);
      |              ^~~~~~
<source>:13:24: note: the temporary was destroyed at the end of the full
expression 'f((* & a), B(42))'
   13 |     const A& result =3D f(a, 42);
      |                       ~^~~~~~~=