220 4873 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 21:06:11 -0400 Lines: 43 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 1370394374 11849 80.91.229.3 (5 Jun 2013 01:06:14 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 5 Jun 2013 01:06:14 +0000 (UTC) To: "std-proposals@isocpp.org" Original-X-From: std-proposals+bncBCUILMGRQMARBBE6XKGQKGQERASKP4Q@isocpp.org Wed Jun 05 03:06:14 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ea0-f200.google.com ([209.85.215.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uk2B3-0001p3-Ef for gclcip-std-proposals@m.gmane.org; Wed, 05 Jun 2013 03:06:13 +0200 Original-Received: by mail-ea0-f200.google.com with SMTP id q15sf867013ead.11 for ; Tue, 04 Jun 2013 18:06:13 -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=ZTDkDeeRFFsIZ9XbM4n/h79fmXMBOY6iVbkSw4TNiD4=; b=nWn0MuqeQgecI9h5yjT4SITF5BM7Q/MS2tkM47YGk5RyTiUb1AA2EsvkSSWqhME5SW 8ZD6MKPy2Uvvg5tAHpKk7v8VVwFEVU9/BM18J3q+vimkkw4avKmtEmJ/lvBOzKB0HsQh Hco+HIpV6cPgVgRQRITGFFYlBVFBiJOe41lRCWHHW9Ae4DiUrjOkZYlCT0mI3/FUMlJ3 kGhcmKsO7h5WCw8XMwp/sFTaMWSlHSTiu/nbaWUbXSjGUG5gHWpZBZEf1V9QRrrrel8b DwmHoemuE1WvHBlc+mOwDxpsRcUkCtjPArUCa3C+kqgkzcSBbOijl7mMgL6Sh2AHKDDH sCgQ== X-Received: by 10.152.28.69 with SMTP id z5mr7102400lag.5.1370394372828; Tue, 04 Jun 2013 18:06:12 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.29.233 with SMTP id n9ls37058lah.101.gmail; Tue, 04 Jun 2013 18:06:11 -0700 (PDT) X-Received: by 10.152.121.73 with SMTP id li9mr14130286lab.18.1370394371905; Tue, 04 Jun 2013 18:06:11 -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 o7si12122941lae.142.2013.06.04.18.06.11 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Jun 2013 18:06:11 -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 d10so1335633lbj.14 for ; Tue, 04 Jun 2013 18:06:11 -0700 (PDT) X-Received: by 10.112.201.67 with SMTP id jy3mr13150420lbc.75.1370394371509; Tue, 04 Jun 2013 18:06:11 -0700 (PDT) Original-Received: by 10.112.146.99 with HTTP; Tue, 4 Jun 2013 18:06:11 -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:4873 Archived-At: On Tue, Jun 4, 2013 at 8:25 PM, Jeffrey Yasskin wrote: > See "The only time const might allow optimizations" in the very > article you linked to. This is for a different reason: the compiler regards the value as a real 'constant', but distinguishes it from a 'real' 'real' one defined in language (and this is why the `constexpr` keyword is there). Try this: struct A { A() : x(10) {} int x; }; void f(int* x) { std::cin >> *x; } int main() { A a; f((int*)&a); std::cout << a.x; } Then you will find that the 'optimization' no longer works. -- 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. .