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 E61EA386F477; Thu,  4 Jun 2020 16:05:18 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E61EA386F477
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1591286718;
 bh=J0oiMxbdUxxtJaydVF6UOESouiwQNebWDDBkToqRegA=;
 h=From:To:Subject:Date:In-Reply-To:References:From;
 b=oqlVGHnsSsVAs5YrZ84fr092BRiSlELp8PzHfoQap+Pu+LwB2hKUyVMuQ0A2yUkge
 HcclxUMqPEhp2zbw10CbMKhssrF8Zsv8LAJX8Q1jPGL60u4500u2iK5k7QvAUTjz+e
 NwYpvqPubLgDVE68QzQEJJHU87ZkbwlFBs5iuCho=
From: "andrew2085 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/95349] Using std::launder(p) produces unexpected behavior
 where (p) produces expected behavior
Date: Thu, 04 Jun 2020 16:05:18 +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: 10.1.0
X-Bugzilla-Keywords: alias, wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: andrew2085 at gmail 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: 
Message-ID: <bug-95349-4-6Pg1gMngIy@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-95349-4@http.gcc.gnu.org/bugzilla/>
References: <bug-95349-4@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: <http://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: <http://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Thu, 04 Jun 2020 16:05:19 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95349

--- Comment #33 from Andrew Downing <andrew2085 at gmail dot com> ---
Those are all perfectly good arguments, but the problem ended up not having
anything to do with std::launder or new implicit object creation rules or
anything else introduced in the most recent standards right? This should be
well defined in c++11 and on https://godbolt.org/z/w5FoZN. It compiles
correctly until gcc 5.1, and in all versions of the other major compilers I=
've
tried that will actually compile on godbolt.org. As far as I can tell, it
should also be well defined in c++98 and on if you use different types and
check the size and alignment some other way.=