220 14507 <1836076.4N961PB4hM@tjmaciei-mobl4> article Path: news.gmane.org!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Range-based if Date: Wed, 12 Nov 2014 13:34:08 -0800 Lines: 37 Approved: news@gmane.org Message-ID: <1836076.4N961PB4hM@tjmaciei-mobl4> References: <1475323.QBNzPAHAPV@tjmaciei-mobl4> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1415828089 30038 80.91.229.3 (12 Nov 2014 21:34:49 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 12 Nov 2014 21:34:49 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRB4FER6RQKGQEMLMBVPQ@isocpp.org Wed Nov 12 22:34:44 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wg0-f69.google.com ([74.125.82.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XofYn-0007Yp-PS for gclcip-std-proposals@m.gmane.org; Wed, 12 Nov 2014 22:34:41 +0100 Original-Received: by mail-wg0-f69.google.com with SMTP id l18sf7146677wgh.0 for ; Wed, 12 Nov 2014 13:34:41 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:subject:date:message-id:user-agent :in-reply-to:references:mime-version:content-type:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=9ra/uANPxfckuna0/E6p+7g8xBeqaHUUQv0r10kBwIY=; b=eBkRkcsNLhX3KSjxTL7/CmJpf9kBzkbpvIXyyhiE3G38eIDSfxHQv7EZK8L+j2Hivt nwHCfHMB+Bzsl2qHhvmMHtz9QHMSW3xxzoLYJW6kvnFNjs5iX9Mh88iXych+2DGoFYDl OJWFwsd7DtI+JMlvcmIVI9WMvGOawOdrw3ML0UFsV7PuKfbybjSXkfoIV/Oowm6Jql/X c9jEIxZlS4YpCIMZrSnJcVszru1mE1Pr4Un35cVy9zcIy1bZgYMi2wMacdgSy2OhDbYH i57cd/OKTXeHIpq5Z5oL0AZUaBTFxcDuAhBXWXadhO3ub+eFqBmIqFPpmrwqkxjsCMeC lGKQ== X-Gm-Message-State: ALoCoQm7F4Mg4MNYPgNwpGXNMKBIBj2zdHryvSlzsLQy1ZHp6mv7j3SGZmNsOv9Fxo/FfZnx5qbu X-Received: by 10.112.188.199 with SMTP id gc7mr3297998lbc.6.1415828081510; Wed, 12 Nov 2014 13:34:41 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.88.194 with SMTP id bi2ls436312wib.53.canary; Wed, 12 Nov 2014 13:34:40 -0800 (PST) X-Received: by 10.180.75.38 with SMTP id z6mr8623289wiv.81.1415828080291; Wed, 12 Nov 2014 13:34:40 -0800 (PST) Original-Received: from gondolin.macieira.info (gondolin.macieira.info. [78.47.120.188]) by mx.google.com with ESMTP id u13si41921215wjr.12.2014.11.12.13.34.40 for ; Wed, 12 Nov 2014 13:34:40 -0800 (PST) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) client-ip=78.47.120.188; Original-Received: from tjmaciei-mobl4.localnet (jfdmzpr06-ext.jf.intel.com [134.134.137.75]) by gondolin.macieira.info (Postfix) with ESMTPSA id A37AB11BDCE for ; Wed, 12 Nov 2014 13:34:38 -0800 (PST) User-Agent: KMail/4.14.2 (Linux/3.16.6-2-desktop; KDE/4.14.2; x86_64; ; ) In-Reply-To: X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) smtp.mail=thiago@macieira.org 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:14507 Archived-At: On Wednesday 12 November 2014 00:50:42 Brent Friedman wrote: > > I must be missing something: what wasn't reachable? > > When you break on the first iteration, the code that advances the iterator > can never be executed. We see this both for 'normal' for loops and for > range-for loops. So what? All the lines got executed. The fact that some assembly instructions did not get executed is not important. You should also report a missed optimisation opportunity bug report to your compiler, as it should be able to realise that the code will never loop and forego emitting the code that does the looping. > It might be easy to say that this is something that vendors should fix, but > I think that the warning is good and valuable as it is. By turning on this > warning we've found a few places where the premature loop exit was actually > unintentional. This is why I think a different control structure might be a > better solution. It can make intent clearer to man and machine. I agree I would have written the code differently, but I don't think overloading the if command for this purpose is the right thing to do. I'd reserve if (x : y) for some other, future purpose. -- Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center PGP/GPG: 0x6EF45358; fingerprint: E067 918B B660 DBD1 105C 966C 33F5 F005 6EF4 5358 -- --- 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/. .