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 42C543858288; Wed, 30 Nov 2022 23:38:40 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 42C543858288
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1669851520;
	bh=l13bBDFtzADyNfhoalNktyLnGHNRkpq5ihrlWlJFQcI=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=SqTOEVjc1vTvdC3kq+XNQU/jAjEbl7Pxkan0h/bp31HokfdjZpV4PplNkG5IgrEMF
	 sQBw4HT8lfm1Wo0RKVZ8ixzgID7kCn3aPM+U2Km/W66rB/QQaId/7RutftWj1tH3vb
	 6r0vVEuSpAuWmJkOTQnliuykH6Rva8qz3FhMLzEw=
From: "iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/99576] [coroutines] destructor of a temporary called too
 early within co_await expression
Date: Wed, 30 Nov 2022 23:38:39 +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: 10.2.1
X-Bugzilla-Keywords: C++-coroutines, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: iains at gcc dot gnu.org
X-Bugzilla-Status: NEW
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: 
Message-ID: <bug-99576-4-9ZPHcf7BpX@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-99576-4@http.gcc.gnu.org/bugzilla/>
References: <bug-99576-4@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=3D99576

--- Comment #14 from Iain Sandoe <iains at gcc dot gnu.org> ---
(In reply to Iain Sandoe from comment #13)
> (In reply to Adrian Perl from comment #12)
> > I have sent the patch and tests to gcc-patches@gcc.gnu.org
>=20
> As noted there, the patch causes regressions in more complex library code
> (e.g. some tests in folly) where CONSTRUCTOR trees might have nested await
> expressions.
>=20
> I mentioned that the real problem is to determine if a temporary should be
> promoted - and, in the case of PR95736, the issue is that we promote a
> temporary for a target expression that is subsequently elided; we can see
> this clearly if we print the object addresses in the test case:
>=20
> START TASK
>  Foo() 0x600001004071
> IN LAMBDA
> ~Foo() 0x600001004070  << corresponds to the elided target expression.
> ~Foo() 0x600001004071
>=20
>=20
> so this:
> diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
> index ce7cf971e03..1bad509233c 100644
> --- a/gcc/cp/coroutines.cc
> +++ b/gcc/cp/coroutines.cc
> @@ -2830,6 +2830,7 @@ find_interesting_subtree (tree *expr_p, int *dosub,
> void *d)
>         }
>      }
>    else if (tmp_target_expr_p (expr)
> +          && !TARGET_EXPR_ELIDING_P (expr)
>            && !p->temps_used->contains (expr))
>      {
>        p->entry =3D expr_p;
>=20
>=20
> fixes that specific problem - but regresses other test cases (no detailed
> analysis yet). Needs more thought ....

Turns out the regression was caused by another patch; given Jason's comment=
 on
the gcc-patches thread, this seems worth testing more widely.=