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 A13643858D39; Wed, 29 Mar 2023 07:11:07 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A13643858D39
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1680073867;
	bh=1HC/jq8vte6hwPbMW3oqUf84JfkqW2B5X/12N8+m+PU=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=hDXf8nDhnuuCQG3ng5f0cVsQT3BITKVrTeZp719i3fk+UMbBPv1y1pKkabZxNUSjE
	 0ocdPa3+WQtjm4CrX/aEbCrjnXo1wGD8As5F1QHnA3jBbb3jYpMbiCAbsv4SqpuO3X
	 vJYBe2vfCrTvX1gCIJSQU+kZn0d6zGwgpg7oBgwk=
From: "StevenSun2021 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/109283] Destructor of co_yield conditional argument called
 twice
Date: Wed, 29 Mar 2023 07:11:07 +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: 12.2.0
X-Bugzilla-Keywords: C++-coroutines, ice-on-valid-code, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: StevenSun2021 at hotmail 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: cc
Message-ID: <bug-109283-4-ZZ3iOFExWq@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-109283-4@http.gcc.gnu.org/bugzilla/>
References: <bug-109283-4@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=3D109283

Steven Sun <StevenSun2021 at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |StevenSun2021 at hotmail d=
ot com

--- Comment #1 from Steven Sun <StevenSun2021 at hotmail dot com> ---
It is indeed a bug. I currently only investigated into the gcc-12, it gener=
ates
something for

```
struct S{ /**/ };
bool w;

co_yield w ? S{"a"} : S{"b"};

```

pseudo-code for the generated gimple:

```
char __res[sizeof(S)];
char __a[sizeof(S)];
char __b[sizeof(S)];

new (__a) S("a");
new (__b) S("b");

if (w)
    memcpy(__res, __a, sizeof(S));
else
    memcpy(__res, __b, sizeof(S));

/*

...

*/

__b->~S();
__a->~S();
__c->~S();

```

So, clearly there is at least 3 bugs here:
i.   `__res` is never constructed.
ii.  only one of the `__a` and `__b` should be constructed, not both.
iii. the assignment is not corrected (it uses `gimple_assign` for value cop=
y).=20

If the ii is correctly implemented, iii will not happen.

Though, the code will work fine on all trivial types.

The correct code should be

```
char __res[sizeof(S)];

if (w)
    new (__res) S("a");
else
    new (__res) S("b");

/*

...

*/

__res->~S();

```=