220 12380 article Path: news.gmane.org!not-for-mail From: Nevin Liber Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Local variables that overstay their welcome Date: Wed, 20 Aug 2014 10:19:36 -0500 Lines: 78 Approved: news@gmane.org Message-ID: References: <778b6fbf-3b58-488c-9e51-32a05b95831e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c3b02e3c29130501112449 X-Trace: ger.gmane.org 1408548025 8954 80.91.229.3 (20 Aug 2014 15:20:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 20 Aug 2014 15:20:25 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBCE35H5S6IDBBMXZ2KPQKGQEIQT2SXY@isocpp.org Wed Aug 20 17:20:19 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wi0-f200.google.com ([209.85.212.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XK7gR-00051h-14 for gclcip-std-proposals@m.gmane.org; Wed, 20 Aug 2014 17:20:19 +0200 Original-Received: by mail-wi0-f200.google.com with SMTP id d1sf3897408wiv.7 for ; Wed, 20 Aug 2014 08:20:18 -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:sender: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=8OOpFNh/HvH2Gg1oMcXz/5t/u+QAWrA2jf0IYOafc7Q=; b=LTr27iXE8LHkyvnpa0V3JdPqJdi/ZL8XW9mrRLO6E6i51LJPh9vR0TSQlpZgoBClha WS4LaGIkacJQIY/9YUMddBVD2lDarYMnfOivO5FtIgqdEAG9EzHDsZ9QAYHvYMQrnunr 3nhkiFRyQ8+bTJu1lJO75EcmVfviQgvtYOO9720jM7GZhNNL+DQ/5Eon7Im/rM0j38up dtNtVxkLmRGHu/0hoDQ5ZwG9djgh0mN+7OQFV+9fjEywOue1uhD/4s6aTwKuHK0vcPy6 H8wC/MDjnF/sekxpzUKWLW4MO/5vZnVvEfxFCM/mvy40GH4YBsP2H4M1lZxeaM8CN0XM bXGQ== X-Gm-Message-State: ALoCoQmuwcgWwHUtosc1xxZh2OgO3rDYzK4C4ItsUO0D9mZESbjz+kH62PTZolf8epZVr6icFMj8 X-Received: by 10.180.198.172 with SMTP id jd12mr1331396wic.6.1408548018417; Wed, 20 Aug 2014 08:20:18 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.126.68 with SMTP id mw4ls133408wib.49.gmail; Wed, 20 Aug 2014 08:20:17 -0700 (PDT) X-Received: by 10.180.182.67 with SMTP id ec3mr16014432wic.21.1408548017811; Wed, 20 Aug 2014 08:20:17 -0700 (PDT) Original-Received: from mail-we0-x22c.google.com (mail-we0-x22c.google.com [2a00:1450:400c:c03::22c]) by mx.google.com with ESMTPS id h3si5087009wix.19.2014.08.20.08.20.17 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 20 Aug 2014 08:20:17 -0700 (PDT) Received-SPF: pass (google.com: domain of nliber@gmail.com designates 2a00:1450:400c:c03::22c as permitted sender) client-ip=2a00:1450:400c:c03::22c; Original-Received: by mail-we0-f172.google.com with SMTP id x48so8108363wes.3 for ; Wed, 20 Aug 2014 08:20:17 -0700 (PDT) X-Received: by 10.194.221.74 with SMTP id qc10mr59200323wjc.39.1408548017545; Wed, 20 Aug 2014 08:20:17 -0700 (PDT) Original-Sender: nliber@gmail.com Original-Received: by 10.194.242.198 with HTTP; Wed, 20 Aug 2014 08:19:36 -0700 (PDT) In-Reply-To: X-Original-Sender: nevin@eviloverlord.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of nliber@gmail.com designates 2a00:1450:400c:c03::22c as permitted sender) smtp.mail=nliber@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:12380 Archived-At: --001a11c3b02e3c29130501112449 Content-Type: text/plain; charset=UTF-8 On 20 August 2014 10:12, Matthew Fioravante wrote: > I'm not sure this is actually possible for static analysis tools. There > can be cases where you want use the value after it is moved from. > > auto x = std::make_unique(); > if(something) { > v.push_back(std::move(x)); > } > foo(x.get()); //Ok: if something was true then foo gets passed a nullptr, > which is what we want > Teaching people to count on the moved-from state is a bad idea. Generally, you should only call functions that have no preconditions (such as assignment and reset); otherwise, users will get confused about what moved-from means. -- Nevin ":-)" Liber (847) 691-1404 -- --- 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/. --001a11c3b02e3c29130501112449 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On 20 August 2014 10:12, Matthew Fioravante <fmatthe= w5876@gmail.com> wrote:
I'm not= sure this is actually possible for static analysis tools. There can be cas= es where you want use the value after it is moved from.
=C2=A0
auto x =3D std::make_unique<= int>();
if(something) {
=C2=A0 v.push_back(std::move(= x));
}
foo(x.get()); //Ok: if something was true then f= oo gets passed a nullptr, which is what we want

Teaching people to count on the move= d-from state is a bad idea. =C2=A0Generally, you should only call functions= that have no preconditions (such as assignment and reset); otherwise, user= s will get confused about what moved-from means.
--
=C2=A0Nevin ":-)" Liber=C2=A0 <mailto:nevin@eviloverlord.com= >=C2=A0 (847) 691-1404

--

---
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/<= /a>.
--001a11c3b02e3c29130501112449-- .