220 36468 <55bb7162-834a-4ba4-bd68-915470842430@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: olafvdspek@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Treating local variables as rvalues in return statements Date: Wed, 3 Jan 2018 02:51:05 -0800 (PST) Lines: 63 Approved: news@gmane.org Message-ID: <55bb7162-834a-4ba4-bd68-915470842430@isocpp.org> References: <4ff5fe2d-0945-491f-9888-479b8e866ace@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2553_329857212.1514976665987" X-Trace: blaine.gmane.org 1514976552 14027 195.159.176.226 (3 Jan 2018 10:49:12 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 3 Jan 2018 10:49:12 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC5NB45SSABBBGXLWLJAKGQEVKGQYEY@isocpp.org Wed Jan 03 11:49:08 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ot0-f200.google.com ([74.125.82.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eWgbY-00039n-EX for gclcip-std-proposals@m.gmane.org; Wed, 03 Jan 2018 11:49:04 +0100 Original-Received: by mail-ot0-f200.google.com with SMTP id r31sf603969otc.9 for ; Wed, 03 Jan 2018 02:51:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=lGwom5ZtM9hmxQBcM1m8fxveSLJoBaOfEFuoYE4FG3M=; b=YBgiOmbPNVTI6p/alsJp74XoeTgYqt4sMuHOx61n5g68FSSHm6ucS7xbOKcYKVFTrn f8CHHTzNx7t+ND9lhrVklR0xbLTLJU5fPPixDhZhf2DES62pk6oA5U+w3H9HfpwXkJLp J3xbFjfOenTwb5d5O6VS5AD4k3ToGBNuysy4ufG+Gqf0zj8pqSvLR2/KofL1tM5W+aTw BqKKUNGK/3pzRgX46TKiWpSgutuQNK9X62sA0S2aw10KG3Ny2mrQFjvHF3yDVx58EuKs tBy3yBjBWgVPNsqsmDCPS35VwSTPkrpsl1rI0lCEqWGtKyB7IKUUkcftbY/nNijSzOgr KPFQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=lGwom5ZtM9hmxQBcM1m8fxveSLJoBaOfEFuoYE4FG3M=; b=LvunA/ozpzJDAqn5UF7d4oP8v4P4BI/LjEYZPDXKG3FnaiGY1cCFrXOHxxNWSIJzQE +yIHo2YTBtLMh1GBsLDZIJnlyC/QsGz77D+jPsawTK5uA4fv9b681OGrZCiWLCnCDJzS WZ5rk4FE8Sim9fdlyvbhzrsPdOJv+iSjrzE5Tw1XL90I5Td8aCx0w9qMhugllJSdeVjD dE2wAug4AUZdwhcV5HOFMtyeWZqDzpIXr8klOLFccBtKY9eyEvgWwAxmrDYy25bvOf9T iu65Nv61wEO62p4A0Dizo8afKjFGiCnLoQ2esnigK39kET//8JZ79aiEFGATJ1jMMRgE V6UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=lGwom5ZtM9hmxQBcM1m8fxveSLJoBaOfEFuoYE4FG3M=; b=Q4w6wdxqIt3xHX5b/qBSTbcu5ZhMT/P2bUKGGe6oC2eaqLVnWZUeHEpIq0OqF+LOtG 92LUefCNRpIUh64G+z3ivoCIM7zAIFghPiF9sdoNctAAZtccLa08dUPKwT8a7oJcKok+ m/LCwPZ0rBzh8PjhyFUmEdD1vrVN9RPMgcPwWGY0/w9Kdg4x+RDSv4Svj1pdDfBRHQVx sVlW10P5fF5D17Wh4NZ26o7UKMT+TSarvEtSGMNm1vyZkgzWT3urQqEMCeeJe+wc7lyO bx/jHe/ONhv8H2o0pmNV/Gux14U4QA/6Q+o6blptfnZSnX1b7FQ+IveDXunuqVCgf4Ew xpgA== X-Gm-Message-State: AKGB3mJX+oWeCoedh06qpTT/25PIaC94PHGLVt5UiNCtfpAU3hgNVGcn Fpo6qPj6/vgJzziwmHUkhLFH0g== X-Google-Smtp-Source: ACJfBouduItQIu1qxVh7hvSfzIlJZ4P1Ts7tz77sbP8MDyOZvyPhDiuEdIC0OL/JewFHirweDRA3kA== X-Received: by 10.157.17.229 with SMTP id y34mr444211oty.52.1514976667511; Wed, 03 Jan 2018 02:51:07 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.202.48.151 with SMTP id w145ls7338552oiw.9.gmail; Wed, 03 Jan 2018 02:51:06 -0800 (PST) X-Received: by 10.157.82.97 with SMTP id q33mr64516otg.7.1514976666509; Wed, 03 Jan 2018 02:51:06 -0800 (PST) In-Reply-To: X-Original-Sender: olafvdspek@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:36468 Archived-At: ------=_Part_2553_329857212.1514976665987 Content-Type: multipart/alternative; boundary="----=_Part_2554_1975210151.1514976665987" ------=_Part_2554_1975210151.1514976665987 Content-Type: text/plain; charset="UTF-8" Op dinsdag 26 december 2017 04:17:12 UTC+1 schreef Nicol Bolas: > > But with your proposal, it isn't. If `compute(str)` has an rvalue overload > or an overload that takes a `string` by value, then these two pieces of > code will have fundamentally different behavior. Specifically, it will have* > undefined* behavior, since `str` will have been moved from by the time > `operator+` gets called on it. > Wouldn't the idea be to do the analysis and only consider it a rvalue if it's NOT accessed later in the statement / function? -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/55bb7162-834a-4ba4-bd68-915470842430%40isocpp.org. ------=_Part_2554_1975210151.1514976665987 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


Op dinsdag 26 december 2017 04:17:12 UTC+1 schreef= Nicol Bolas:
=
But with your proposal, it isn't. If `compute(str)` has an rvalue = overload or an overload that takes a `string` by value, then these two piec= es of code will have fundamentally different behavior. Specifically, it wil= l have undefined behavior, since `str` will have been moved from by = the time `operator+` gets called on it.

Wouldn't the idea be to do the analysis and only consider it a= rvalue if it's NOT accessed later in the statement / function?=C2=A0

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