220 4979 article Path: news.gmane.org!not-for-mail From: =?ISO-8859-1?Q?Daniel_Kr=FCgler?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: std::optional - move is conditionally nothrow, what about copy? Date: Tue, 11 Jun 2013 21:56:43 +0200 Lines: 46 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 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1370980606 4879 80.91.229.3 (11 Jun 2013 19:56:46 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 11 Jun 2013 19:56:46 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCT7RVFA4QORB7EB32GQKGQEU5COHEQ@isocpp.org Tue Jun 11 21:56:48 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wi0-f197.google.com ([209.85.212.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UmUgP-00079b-6T for gclcip-std-proposals@m.gmane.org; Tue, 11 Jun 2013 21:56:45 +0200 Original-Received: by mail-wi0-f197.google.com with SMTP id hj3sf2633205wib.0 for ; Tue, 11 Jun 2013 12:56:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere: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:x-google-group-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type:content-transfer-encoding; bh=/H4+G0qy90yJAfhc4TFjNsXcr4D7Nnjjjf/9ZkoDxpo=; b=AdTxf42W7yVrXT5TmEx1ePAiR/RcN3NxIedsyvN6qUqPPE4/Wn+y61eA7wvMBXAK7x Lf3EtPJMD8Qf33FX+l5XkUQW0b4+cct2kaxcI5/5ILQ/LKy4ecXXk8/ZoOlgx4R5R8F1 eO7bNn5WRoVwWCWSfSP6QOOZ1Wvox0EK/H5hKVntt9llcKXPDnEeLUVBBz8LhXf8F++f avzg9E2vLOaHB7dfX+um2C7p1ODtKoLZ+2EMCw0aMsgp+XiNE/qKT8ygKhisVeSnyOTd FLPSiWtApuPdrS6ULShtzzUOrzBpNr6IuNexnxg78JSOB3ejouKE61QWWa4FX5UjuNy3 hSdw== X-Received: by 10.180.95.5 with SMTP id dg5mr1852458wib.6.1370980604920; Tue, 11 Jun 2013 12:56:44 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.95.35 with SMTP id dh3ls1382068wib.7.canary; Tue, 11 Jun 2013 12:56:43 -0700 (PDT) X-Received: by 10.180.81.169 with SMTP id b9mr2398233wiy.12.1370980603706; Tue, 11 Jun 2013 12:56:43 -0700 (PDT) Original-Received: from mail-wg0-x22d.google.com (mail-wg0-x22d.google.com [2a00:1450:400c:c00::22d]) by mx.google.com with ESMTPS id om5si5958091wjc.29.2013.06.11.12.56.43 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 11 Jun 2013 12:56:43 -0700 (PDT) Received-SPF: pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c00::22d as permitted sender) client-ip=2a00:1450:400c:c00::22d; Original-Received: by mail-wg0-f45.google.com with SMTP id j13so963353wgh.24 for ; Tue, 11 Jun 2013 12:56:43 -0700 (PDT) X-Received: by 10.180.206.70 with SMTP id lm6mr2386433wic.50.1370980603638; Tue, 11 Jun 2013 12:56:43 -0700 (PDT) Original-Received: by 10.217.119.134 with HTTP; Tue, 11 Jun 2013 12:56:43 -0700 (PDT) In-Reply-To: X-Original-Sender: daniel.kruegler@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c00::22d as permitted sender) smtp.mail=daniel.kruegler@gmail.com; dkim=pass header.i=@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:4979 Archived-At: 2013/6/11 R=F3bert D=E1vid : > Hello, > > I just noticed that in the last draft, std::optional has a move > constructor that is nothrow(is_nothrow_move_constructible::value), and > has a move-assignment operator that is > nothrow(is_nothrow_move_assignable::value && > is_nothrow_move_constructible::value) (I think move-constructable for = the > case of assigning to a disengaged object). > > Now, there are no similar requirements for the copy constructor. Is there > any reason why is it not nothrow(is_nothrow_copy_constructible::value)= , > and similarly for the move-assignment operator? The rationale for the lack of this specification is that during the introduction of noexcept in the library it was decided that move-operations and swap operations are (a) often noexcept and (b) fundamental enough to justify that they will always get a - possibly conditional - exception specification. Copying is fundamental, but it generally has not a fundamental restriction to be noexcept (see the special assumptionas that the library can make, if move operations may throw exceptions). See also http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3279.pdf were a set of guidelines was suggested. - Daniel --=20 ---=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. 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