From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-patches-return-333330-listarch-gcc-patches=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 18774 invoked by alias); 2 Dec 2012 12:32:23 -0000
Received: (qmail 18763 invoked by uid 22791); 2 Dec 2012 12:32:23 -0000
X-SWARE-Spam-Status: No, hits=-2.7 required=5.0	tests=BAYES_00,FREEMAIL_FROM,KHOP_THREADED,RCVD_IN_DNSWL_NONE,RCVD_IN_HOSTKARMA_NO,RCVD_IN_HOSTKARMA_YE,RDNS_NONE
X-Spam-Check-By: sourceware.org
Received: from Unknown (HELO mailout-de.gmx.net) (213.165.64.23)    by sourceware.org (qpsmtpd/0.43rc1) with SMTP; Sun, 02 Dec 2012 12:31:51 +0000
Received: (qmail invoked by alias); 02 Dec 2012 12:31:43 -0000
Received: from pD9FDE7B1.dip.t-dialin.net (EHLO [192.168.2.21]) [217.253.231.177]  by mail.gmx.net (mp039) with SMTP; 02 Dec 2012 13:31:43 +0100
Message-ID: <50BB4A2D.5050408@gmx.net>
Date: Sun, 02 Dec 2012 12:32:00 -0000
From: Olivier Ballereau <Olivier.Ballereau@gmx.net>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:17.0) Gecko/17.0 Thunderbird/17.0
MIME-Version: 1.0
To: Xinliang David Li <davidxl@google.com>
CC: GCC Patches <gcc-patches@gcc.gnu.org>,  Jason Merrill <jason@redhat.com>, Richard Guenther <richard.guenther@gmail.com>
Subject: Re: New option to turn off stack reuse for temporaries
References: <CAAkRFZK_27tveOTLioz-YwfF_4w4qtTJkRFjno7r8risRVQsnQ@mail.gmail.com>
In-Reply-To: <CAAkRFZK_27tveOTLioz-YwfF_4w4qtTJkRFjno7r8risRVQsnQ@mail.gmail.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 8bit
X-IsSubscribed: yes
Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-patches.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>
List-Post: <mailto:gcc-patches@gcc.gnu.org>
List-Help: <mailto:gcc-patches-help@gcc.gnu.org>
Sender: gcc-patches-owner@gcc.gnu.org
X-SW-Source: 2012-12/txt/msg00072.txt.bz2

Hello David,

Sorry to come so late into the discussion, but...

On 21/06/12 00:50, Xinliang David Li wrote:
> One of the most common runtime errors we have seen in gcc-4_7 is
> caused by dangling references to temporaries whole life time have
> ended
> 
> e.g,
> 
>  const A& a = foo();
> 
> or
> foo (A());// where temp's address is saved and used after foo.
> 
> Of course this is user error according to the standard,
> [...]

... is the first of your 2 examples really a user error? If so, it
breaks GotW #88: A Candidate For the “Most Important const” [1]. Can you
please clarify?

Thanks in advance!
Olivier

[1]
http://herbsutter.com/2008/01/01/gotw-88-a-candidate-for-the-most-important-const/