220 11751 article Path: news.gmane.org!not-for-mail From: "'Jeffrey Yasskin' via ISO C++ Standard - Future Proposals" 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 12:22:13 -0700 Lines: 36 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=ISO-8859-1 X-Trace: ger.gmane.org 1404933759 23302 80.91.229.3 (9 Jul 2014 19:22:39 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 9 Jul 2014 19:22:39 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDDM34EO6QDRB6NM62OQKGQECO35BMY@isocpp.org Wed Jul 09 21:22:35 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qg0-f69.google.com ([209.85.192.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1X4xRq-0008Fg-PR for gclcip-std-proposals@m.gmane.org; Wed, 09 Jul 2014 21:22:35 +0200 Original-Received: by mail-qg0-f69.google.com with SMTP id j107sf18052710qga.8 for ; Wed, 09 Jul 2014 12:22:34 -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:from:date :message-id:subject: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=QOUU0Q00x8Guq5/8Uim67nM4SCVznA7115U+0Mv9wPo=; b=mLjgbgcDDq3bEQbDFYi3wPKAhf9vv6x/wf8NapPuc/5/S6PJe16NOxskONc5rwTzBC 4qnMucvIyg1H8y24gzbsFd3VKeipn0ky8KkrqLgvbNu9ZOILhjT6YWvUvQcxUEoPmZk1 FwiJRFqEnftm7lxSAT0MOQMrZ4YGAE4dejIGjaJzqFK7nOc7PKpjfuiP6ZRJYJ8qB0bo Q3v6ZJ8qsDPhycQ8qFsp5nMcPvyru7FNyRA7UBHKK4/6kk4IDQGKXzwVDeo9chGZ4jfB L/OLgiMYmYYzxQKkIcFZg9+vvi+l3QcY+rGRvOZzLu9ngJL3eTBhfNvE8Epi7PTj0n4l SufA== X-Gm-Message-State: ALoCoQnOS7AHDerHT4yTO0Hmt/iduIGfzFBt/1MR2dd3dTmJhSvrJz5MVOKbHyV0C7hBWhbQdu8K X-Received: by 10.236.164.106 with SMTP id b70mr17872266yhl.1.1404933753956; Wed, 09 Jul 2014 12:22:33 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.105.136 with SMTP id c8ls2568621qgf.76.gmail; Wed, 09 Jul 2014 12:22:33 -0700 (PDT) X-Received: by 10.58.65.40 with SMTP id u8mr12705ves.53.1404933753358; Wed, 09 Jul 2014 12:22:33 -0700 (PDT) Original-Received: from mail-vc0-x232.google.com (mail-vc0-x232.google.com [2607:f8b0:400c:c03::232]) by mx.google.com with ESMTPS id xt7si21996452veb.104.2014.07.09.12.22.33 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 09 Jul 2014 12:22:33 -0700 (PDT) Received-SPF: pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:400c:c03::232 as permitted sender) client-ip=2607:f8b0:400c:c03::232; Original-Received: by mail-vc0-f178.google.com with SMTP id ij19so7945584vcb.23 for ; Wed, 09 Jul 2014 12:22:33 -0700 (PDT) X-Received: by 10.220.5.138 with SMTP id 10mr619971vcv.67.1404933753178; Wed, 09 Jul 2014 12:22:33 -0700 (PDT) Original-Received: by 10.53.11.164 with HTTP; Wed, 9 Jul 2014 12:22:13 -0700 (PDT) In-Reply-To: X-Original-Sender: jyasskin@google.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:400c:c03::232 as permitted sender) smtp.mail=jyasskin@google.com; dkim=pass header.i=@google.com; dmarc=pass (p=REJECT dis=NONE) header.from=google.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: , X-Original-From: Jeffrey Yasskin Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:11751 Archived-At: On Wed, Jul 9, 2014 at 12:20 PM, Ville Voutilainen wrote: > 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. SGTM. Can you file a "NEEDS_DISCUSSION" issue on https://issues.isocpp.org/? We'll also need an NB comment on the PDTS if we're going to fix it for V1. -- --- 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/. .