220 4874 article Path: news.gmane.org!not-for-mail From: Nevin Liber Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: std::sequence Date: Tue, 4 Jun 2013 20:11:24 -0500 Lines: 69 Approved: news@gmane.org Message-ID: References: <4551abbc-43aa-4520-a91a-f8eb25a90588@isocpp.org> <2c8e6079-9c87-425a-93e2-39251df57cd8@isocpp.org> <9f1cace3-0503-4a3c-a8ce-d7546564b3ef@isocpp.org> <1c991e6e-6bc3-4822-9ffd-7f2508e63974@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=047d7b33992dc4951704de5de29d X-Trace: ger.gmane.org 1370394728 15239 80.91.229.3 (5 Jun 2013 01:12:08 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 5 Jun 2013 01:12:08 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCE35H5S6IDBBZNAXKGQKGQETR7QMGA@isocpp.org Wed Jun 05 03:12:08 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vb0-f70.google.com ([209.85.212.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uk2Gl-0006Aw-8A for gclcip-std-proposals@m.gmane.org; Wed, 05 Jun 2013 03:12:07 +0200 Original-Received: by mail-vb0-f70.google.com with SMTP id f13sf1070637vbg.1 for ; Tue, 04 Jun 2013 18:12:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-beenthere: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:x-google-group-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=JNQHZQk5daP9R/xqj0cb8oAgK9v3ebRqSeNR1IXb08I=; b=weQutYSeAuarUU5o6EtXW4na0dnAwnS73jRn4bgE6nccLN4M+3MIOGfaWCmr//c28Q IgoXLmwWTn8RxemjK1HZXWrsqlUd7PWq3ATC6sPTSiLfZLa79SRrvGQ68rnjqr4IamCc aRJSNAh3IUXzaDgIJqaf3Nta811sfM3u7PjNm94OgZouBTbR9wcAougFPx126OtiB03M atRlMaxWb4eHbNhyJP82kJXlzhD2L8rIKZfYubNRUlLm9JkVj9XPQkrqgM2yKkFXSSW+ 07iIyj/UOV/R1xxPLt2/Ps9i4c1oX/oM3G/0p6oKqXXCENK0TBddl6dUjVb2rVB81NPh NU5g== X-Received: by 10.236.92.194 with SMTP id j42mr16883221yhf.38.1370394726304; Tue, 04 Jun 2013 18:12:06 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.63.228 with SMTP id j4ls574385qes.80.gmail; Tue, 04 Jun 2013 18:12:05 -0700 (PDT) X-Received: by 10.224.213.201 with SMTP id gx9mr25777700qab.94.1370394725043; Tue, 04 Jun 2013 18:12:05 -0700 (PDT) Original-Received: from mail-qe0-f41.google.com (mail-qe0-f41.google.com [209.85.128.41]) by mx.google.com with ESMTPS id m3si10818868qcb.149.2013.06.04.18.12.04 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Jun 2013 18:12:04 -0700 (PDT) Received-SPF: pass (google.com: domain of nliber@gmail.com designates 209.85.128.41 as permitted sender) client-ip=209.85.128.41; Original-Received: by mail-qe0-f41.google.com with SMTP id b4so685125qen.14 for ; Tue, 04 Jun 2013 18:12:04 -0700 (PDT) X-Received: by 10.49.11.168 with SMTP id r8mr10599169qeb.34.1370394724699; Tue, 04 Jun 2013 18:12:04 -0700 (PDT) Original-Sender: nliber@gmail.com Original-Received: by 10.49.64.165 with HTTP; Tue, 4 Jun 2013 18:11:24 -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 209.85.128.41 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:4874 Archived-At: --047d7b33992dc4951704de5de29d Content-Type: text/plain; charset=ISO-8859-1 On 4 June 2013 20:06, Zhihao Yuan wrote: > int main() { > A a; > f((int*)&a); > std::cout << a.x; > } > > Then you will find that the 'optimization' no longer works. > > You are invoking undefined behavior, so whether or not the optimization works in this case is irrelevant. -- 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/?hl=en. --047d7b33992dc4951704de5de29d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 4 June 2013 20:06, Zhihao Yuan <lichray@gmail.com> wrote:=
int main() {
=A0 =A0 A a;
=A0 =A0 f((int*)&a);
=A0 =A0 std::cout << a.x;
}

Then you will find that the 'optimization' no longer works.


You are= invoking undefined behavior, so whether or not the optimization works in t= his case is irrelevant.=A0
--
=A0Nevin ":-)" Liber= =A0 <mailto:= nevin@eviloverlord.com>=A0 (847) 691-1404

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