220 4875 article Path: news.gmane.org!not-for-mail From: Zhihao Yuan Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: std::sequence Date: Tue, 4 Jun 2013 21:19:42 -0400 Lines: 34 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: text/plain; charset=ISO-8859-1 X-Trace: ger.gmane.org 1370395184 19353 80.91.229.3 (5 Jun 2013 01:19:44 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 5 Jun 2013 01:19:44 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBCUILMGRQMARBMFEXKGQKGQEF4HADOA@isocpp.org Wed Jun 05 03:19:45 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ee0-f71.google.com ([74.125.83.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uk2O9-0003Ph-3E for gclcip-std-proposals@m.gmane.org; Wed, 05 Jun 2013 03:19:45 +0200 Original-Received: by mail-ee0-f71.google.com with SMTP id e52sf369415eek.10 for ; Tue, 04 Jun 2013 18:19:44 -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; bh=fgBShWjfpul6tQwVBRkoxjvDsZ34zLVs/ESPLAzxQNw=; b=ebSuz/ftljoDslCfK/Ct4CDqDDEKcpghXmbbqSe/nBSd8yLpWlFmYFguQYcRB34hxm qMI9yU1yF9LICXPbhHLw+lY2l7cXMlzVDXIAsQhK/GwsqViXFe9NwZQ2HJ3AMQrJPQul tFuQJ4svVCyiV60DXyP78AHdiaO9l/RbeovwsO5l+MoiPTfx+ytocT85yfpMqRJhdXjy fsk4pxxLInN8M5RtMTYTM1WrENW7cnbSh8mJRJ6jtlKU+GQe6i7Pa3S2o9DNOHt2sQcK 6Uz5NngXq3+l7Ep6TKMsSX0pxuhrJ1GXO+PS6EF76P/gkP/fP5KzNZhzKUQfiwGYjA92 iz0w== X-Received: by 10.112.164.69 with SMTP id yo5mr7253701lbb.6.1370395184495; Tue, 04 Jun 2013 18:19:44 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.19.135 with SMTP id f7ls36591lae.108.gmail; Tue, 04 Jun 2013 18:19:43 -0700 (PDT) X-Received: by 10.112.173.37 with SMTP id bh5mr14015033lbc.110.1370395183089; Tue, 04 Jun 2013 18:19:43 -0700 (PDT) Original-Received: from mail-lb0-f169.google.com (mail-lb0-f169.google.com [209.85.217.169]) by mx.google.com with ESMTPS id 8si2489583lbp.76.2013.06.04.18.19.43 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Jun 2013 18:19:43 -0700 (PDT) Received-SPF: pass (google.com: domain of lichray@gmail.com designates 209.85.217.169 as permitted sender) client-ip=209.85.217.169; Original-Received: by mail-lb0-f169.google.com with SMTP id d10so1343481lbj.14 for ; Tue, 04 Jun 2013 18:19:43 -0700 (PDT) X-Received: by 10.152.29.169 with SMTP id l9mr14340178lah.31.1370395182850; Tue, 04 Jun 2013 18:19:42 -0700 (PDT) Original-Received: by 10.112.146.99 with HTTP; Tue, 4 Jun 2013 18:19:42 -0700 (PDT) In-Reply-To: X-Original-Sender: lichray@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of lichray@gmail.com designates 209.85.217.169 as permitted sender) smtp.mail=lichray@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:4875 Archived-At: On Tue, Jun 4, 2013 at 9:11 PM, Nevin Liber 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. Yes, of course :) The behavior of the program does not prove my argument, but don't forget the program showed on StackOverflow is also a UB. I can only conceptually explain this and hope you can understand... -- Zhihao Yuan, ID lichray The best way to predict the future is to invent it. ___________________________________________________ 4BSD -- http://4bsd.biz/ -- --- 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. .