220 11749 article Path: news.gmane.org!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: N4078: Rvalue reference overloads for value() method returns object by value Date: Wed, 9 Jul 2014 22:20:30 +0300 Lines: 30 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1404933639 21605 80.91.229.3 (9 Jul 2014 19:20:39 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 9 Jul 2014 19:20:39 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5JHI7A7ALRB7VL62OQKGQEWY77BZQ@isocpp.org Wed Jul 09 21:20:34 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f72.google.com ([209.85.220.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1X4xPs-0006ew-JH for gclcip-std-proposals@m.gmane.org; Wed, 09 Jul 2014 21:20:32 +0200 Original-Received: by mail-pa0-f72.google.com with SMTP id rd3sf53117162pab.7 for ; Wed, 09 Jul 2014 12:20:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=mx2rdpg+OSUu/eNYUCSSFJwIPzybQf8avBbUVmN8X3s=; b=VEwX4QCApHc9Bd8up/vmxYJVv/y8H4Ap3ycm6EvleJcGpsIQAG8yR+SB/gDf3tHEhr wRiJ1MRFVgetOtDzdNeX6iKF44N2TslYtf4HRVn3Fa9aJrvvkxu9uTKLUNzHhgRA7CP3 l8zD7ZNEymqEsPf3xmEeOrUvaEuqsQh1Vnc3MS4h6KlJjC0lWhD9ZcLXNKaR05Z6KHsi W2y5NTBKrguAThRUbimG1ZuFam4B/EjCgb4wxrOo99A13dV18pxoxDoelwdiYNgcqSxD qJbXa2Si93Ihu+9XOIjSVNGeR//fOMbQNTdkalaXeZThjDrI0314RWJ44RAyPFkjUf/r edOQ== X-Gm-Message-State: ALoCoQknrPewHsu3oHcoyje/y0P23at9DQCJS/udims1EZudk6IgyqZEpJmRKzF5nYUGfEph3e0v X-Received: by 10.66.169.79 with SMTP id ac15mr13022843pac.48.1404933631515; Wed, 09 Jul 2014 12:20:31 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.39.6 with SMTP id u6ls396622qgu.59.gmail; Wed, 09 Jul 2014 12:20:30 -0700 (PDT) X-Received: by 10.58.234.103 with SMTP id ud7mr41818935vec.24.1404933630654; Wed, 09 Jul 2014 12:20:30 -0700 (PDT) Original-Received: from mail-vc0-x230.google.com (mail-vc0-x230.google.com [2607:f8b0:400c:c03::230]) by mx.google.com with ESMTPS id ad18si22008504vec.43.2014.07.09.12.20.30 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 09 Jul 2014 12:20:30 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c03::230 as permitted sender) client-ip=2607:f8b0:400c:c03::230; Original-Received: by mail-vc0-f176.google.com with SMTP id ik5so7942854vcb.21 for ; Wed, 09 Jul 2014 12:20:30 -0700 (PDT) X-Received: by 10.220.192.129 with SMTP id dq1mr1993232vcb.57.1404933630567; Wed, 09 Jul 2014 12:20:30 -0700 (PDT) Original-Received: by 10.224.31.137 with HTTP; Wed, 9 Jul 2014 12:20:30 -0700 (PDT) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c03::230 as permitted sender) smtp.mail=ville.voutilainen@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:11749 Archived-At: On 9 July 2014 22:09, 'Jeffrey Yasskin' via ISO C++ Standard - Future Proposals wrote: > http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1651 addresses: > > std::pair g(); > auto&& s = g().first; //will create a dangling reference > > It's in 'ready' status, meaning it's not in C++14, but it's likely to get > fixed immediately after, possibly as a "defect", which would mean that most > compilers would implement the fix in their C++14 modes. > > I agree that I'd rather see the general issue fixed by a language change > (probably involving a change to the library to use the new language > feature). I'm ambivalent about the safety fix we have in optional<>. I think the "yes, moving twice is fine, but what if the move ends up copying?" issue and the "perfect-forwarding the underlying value from an optional becomes tricky" issue are worth discussing in LEWG. They certainly change my (minor) preference. -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. .