220 19778 article Path: news.gmane.org!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Move destructor draft Date: Tue, 11 Aug 2015 10:42:17 -0400 Lines: 38 Approved: news@gmane.org Message-ID: References: <0A99E209-333B-4140-8F65-2F022E681AC1@gmail.com> <55C0DDD4.8090100@halpernwightsoftware.com> <411A67D7-B062-4D22-983A-095737483208@gmail.com> <55C299B0.1060300@gmail.com> <55C2ABA3.8060605@halpernwightsoftware.com> <55C2ECDB.1060307@gmail.com> <5de71605-7320-4130-938b-813304c51069@isocpp.org> <94331665-f7f3-444b-a1dc-333a52be7873@isocpp.org> <5A4BB28D-A1EE-4B78-99FF-6BCFEA7E2FF3@gma il.com> <1384fc7c-3e1e-439a-9ada-8ec2ff48cc2d@isocpp.org> <8c7ed362-5609-4176-a5bb-a68798e2e71d@isocpp.org> 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 1439304316 22275 80.91.229.3 (11 Aug 2015 14:45:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 11 Aug 2015 14:45:16 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBB44UVCXAKGQEISILVAQ@isocpp.org Tue Aug 11 16:45:08 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wi0-f198.google.com ([209.85.212.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZPAnc-0007KF-43 for gclcip-std-proposals@m.gmane.org; Tue, 11 Aug 2015 16:45:08 +0200 Original-Received: by wicul11 with SMTP id ul11sf50440435wic.1 for ; Tue, 11 Aug 2015 07:45:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:to:from:subject:date:lines:message-id:references :mime-version:content-type:user-agent:in-reply-to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=l4Qb34c1GhspZq/y+8nRd47CPbQqv/4OmYAtxcYYz0c=; b=SyRUVSzQ9uue2rTDNL/9k9Mi5TqEEIlBLtGsfhjc4PYgG3tf4MGZMmpgvLhDufpcIZ k+QKGQVd6gDwPcC+xnrdrTpWcL/Ios3jMJm52jxOoJZhfOCoGuZH9cqoKfLpyTVzPJhj iMU38IZ8qeoHcVqSHUv8m0s6egFpu4KAiTbM7+dW7nPBY0YVjqzC2As3XJg6UXjXM/SV 7ICc7Z65t2zwf+RwMsIcymfEv42vFPHlVCnEVb4jjiFayVxZcBSAWfv0bQPJ5+t275VY juO9Mn4+qjUlo6f87eZMOr0rmlMA79s6mZqrB4qgW1kpLuxKFGwX7yTvKXMdzNTB/iiq X-Gm-Message-State: ALoCoQnaUQbxuUhPeg3hpOnYTIGcNMw/qCkr22unVDij93snJdPFyWvJsL49y6QLy1ePuN++nKuW X-Received: by 10.112.90.225 with SMTP id bz1mr456938lbb.12.1439304307647; Tue, 11 Aug 2015 07:45:07 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.5.39 with SMTP id p7ls806047lap.104.gmail; Tue, 11 Aug 2015 07:45:06 -0700 (PDT) X-Received: by 10.152.6.65 with SMTP id y1mr12558921lay.58.1439304306339; Tue, 11 Aug 2015 07:45:06 -0700 (PDT) Original-Received: from plane.gmane.org (plane.gmane.org. [80.91.229.3]) by mx.google.com with ESMTPS id x8si1523760laj.25.2015.08.11.07.45.06 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 11 Aug 2015 07:45:06 -0700 (PDT) Received-SPF: pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) client-ip=80.91.229.3; Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ZPAnZ-0007JH-71 for std-proposals@isocpp.org; Tue, 11 Aug 2015 16:45:05 +0200 Original-Received: from tripoint.kitware.com ([66.194.253.20]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 11 Aug 2015 16:45:05 +0200 Original-Received: from mwoehlke.floss by tripoint.kitware.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 11 Aug 2015 16:45:05 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 29 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: tripoint.kitware.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 In-Reply-To: <8c7ed362-5609-4176-a5bb-a68798e2e71d@isocpp.org> X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) smtp.mailfrom=gclcip-std-proposals@m.gmane.org; dmarc=fail (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-Spam-Checked-In-Group: std-proposals@isocpp.org 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:19778 Archived-At: On 2015-08-09 21:14, jgottman6@gmail.com wrote: > Very nice, but I have one question. How do you handle member variables > that might or might not be self-references? For instance, in your example, > if the variable a is guaranteed to be either equal to this or a pointer to > an object allocated with new, how would you write the relocator function? > Most other members of class A could have code like > > if (a == this) { > //do something > } else { > //do something else > } > > but in the case of the relocator function, by the time we get to the a > variable half the object has been relocated and it's not at all obvious > what needs to be tested. You would compare to the old object location rather than 'this'. Examples like these are why if we were to have a separate fix-up operator (i.e. able to "mostly" construct the new objects via memcpy), it would need the original object address and *possibly* also need for that memory to be unmodified. With a one-at-a-time relocation operator/ctor/whatever you don't run into these sorts of problems, although it does penalize the case of such classes somewhat. -- Matthew -- --- 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/. .