220 14140 <2027575.4qiFzyj4qf@tjmaciei-mobl4> article Path: news.gmane.org!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: #pragma once Date: Wed, 22 Oct 2014 15:44:49 -0700 Lines: 39 Approved: news@gmane.org Message-ID: <2027575.4qiFzyj4qf@tjmaciei-mobl4> References: <3d0ab5b0-73d9-434a-9ae4-cd47d8275590@isocpp.org> <67e8e595-bc97-496a-b656-474cb093b940@isocpp.org> <4039b7bf-7177-4863-ae3f-3b81b0cfb435@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 1414017901 23705 80.91.229.3 (22 Oct 2014 22:45:01 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 22 Oct 2014 22:45:01 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBZPGUCRAKGQE4QLK23Q@isocpp.org Thu Oct 23 00:44:56 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 1Xh4eE-0001DH-TH for gclcip-std-proposals@m.gmane.org; Thu, 23 Oct 2014 00:44:54 +0200 Original-Received: by mail-wg0-f69.google.com with SMTP id b13sf2582470wgh.8 for ; Wed, 22 Oct 2014 15:44:54 -0700 (PDT) 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:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=kedXL8/e75HkU4vsRXmV9cvmGCGOymrZWz8kQpe4UNg=; b=erDm8ds6sDV04wgS5ra4vs1A5E3WUWd0XzzQgfUltN60mh8PbSbi+xyQudv4tYe3LG NUQu2sDU+KC4nqIAev+m/Lx9NEu1itSm1T4QSCPHh2V8zTsIGl/9DQFMv5SFU04CAqTw AwXDU8Sq64t4hPXGh11mRg7kvNqKiOF8kRyfBtNcfu0NGISaQfmYy9HPEnfl50VyqFME Mkek/VVOXK3YnvEvagsKwAJiiHOAxTKu3GpUv3i5sVPokbR4e501dTCHCeHQsENbDQbI LrL2WUibIcmbq0rm7Y7PugTcJFxHQvHK6A7D2p8OYeULdbr6+YZ37Sr08iUGlhChYfbS z8kQ== X-Gm-Message-State: ALoCoQkZASMpXYj6VvarxH6DbK70GIdsYHcxiFmlwk3sZbxCj20mhp937hFGkoVvE/EPeaB62oaR X-Received: by 10.181.11.130 with SMTP id ei2mr1529908wid.3.1414017894500; Wed, 22 Oct 2014 15:44:54 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.37.1 with SMTP id u1ls273173laj.29.gmail; Wed, 22 Oct 2014 15:44:52 -0700 (PDT) X-Received: by 10.112.38.67 with SMTP id e3mr1101769lbk.6.1414017892556; Wed, 22 Oct 2014 15:44:52 -0700 (PDT) Original-Received: from gondolin.macieira.info (gondolin.macieira.info. [78.47.120.188]) by mx.google.com with ESMTP id l5si104239lag.57.2014.10.22.15.44.52 for ; Wed, 22 Oct 2014 15:44:52 -0700 (PDT) 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 (jfdmzpr02-ext.jf.intel.com [134.134.137.71]) by gondolin.macieira.info (Postfix) with ESMTPSA id 70B7C11B5DA for ; Wed, 22 Oct 2014 15:44:51 -0700 (PDT) User-Agent: KMail/4.14 (Linux/3.11.10-21-desktop; KDE/4.14.0; x86_64; ; ) In-Reply-To: <4039b7bf-7177-4863-ae3f-3b81b0cfb435@isocpp.org> 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:14140 Archived-At: On Wednesday 22 October 2014 14:27:56 Myriachan wrote: > I would specify #pragma once's behavior to be unspecified (but either > include or not include) in the event that the implementation cannot > reliably determine whether two files coincide. If you want your code to > work, don't create a situation where you expect a file to not be > double-included when the codebase accesses it through two different mount > points for which the OS cannot identify them as identical or overlapping. Sorry, but I don't think that's useful. If you leave the behaviour unspecified, it isn't useful because we can't guarantee it will work. I can't mandate where people should store my source code. Therefore, I can't guarantee that the source code I write will work on their computers. That means the feature is useless. > Sometimes #include guards have problems. You can easily run into cases > where two unrelated headers think they're both the same name. That can't happen, since you can't #include two different headers with the same name (#include_next doesn't count). Each include should have its canonical #include mechanism. If you a header is #include'd with , then the include guard should have both the words "module" and "header" in the include guard. -- 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/. .