220 4870 article Path: news.gmane.org!not-for-mail From: Jeffrey Yasskin Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: std::sequence Date: Tue, 4 Jun 2013 17:25:41 -0700 Lines: 28 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 1370391964 22668 80.91.229.3 (5 Jun 2013 00:26:04 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 5 Jun 2013 00:26:04 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDDM34EO6QDRBG4LXKGQKGQEHMLCBUA@isocpp.org Wed Jun 05 02:26:05 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f200.google.com ([209.85.214.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Uk1YC-00064X-UK for gclcip-std-proposals@m.gmane.org; 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spf=pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:4001:c03::22e as permitted sender) smtp.mail=jyasskin@google.com; dkim=pass header.i=@google.com; dmarc=pass (p=REJECT dis=none) d=google.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:4870 Archived-At: On Tue, Jun 4, 2013 at 5:17 PM, Zhihao Yuan wrote: > On Tue, Jun 4, 2013 at 7:26 PM, Jeffrey Yasskin wrote: >> const array_ref carr2 = ...; >> do_stuff_with(carr2); >> use(carr2.size()); >> >> the compiler _can_ assume carr.size() is the same. > > In a general case, since the same memory can be referred > by another pointer or reference, optimizers just won't analysis > the data flow. Instead, they know many thing about the control > flow. If the above code is optimized, that means you don't > have the code to change the size; it doesn't matter you declare > it as const or not. See "The only time const might allow optimizations" in the very article you linked to. -- --- 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. .