220 14135 article Path: news.gmane.org!not-for-mail From: Bo Persson Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: #pragma once Date: Wed, 22 Oct 2014 20:43:56 +0200 Lines: 46 Approved: news@gmane.org Message-ID: References: <3d0ab5b0-73d9-434a-9ae4-cd47d8275590@isocpp.org> <202c5550-8669-4b45-aa39-9a8d26c37015@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed X-Trace: ger.gmane.org 1414003461 5383 80.91.229.3 (22 Oct 2014 18:44:21 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 22 Oct 2014 18:44:21 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCZ6RLW3UIKBB7HVT6RAKGQE5GDEK3Y@isocpp.org Wed Oct 22 20:44:14 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wi0-f198.google.com ([209.85.212.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Xh0tK-00067Z-1P for gclcip-std-proposals@m.gmane.org; Wed, 22 Oct 2014 20:44:14 +0200 Original-Received: by mail-wi0-f198.google.com with SMTP id n3sf8108wiv.5 for ; Wed, 22 Oct 2014 11:44:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:to:from:subject:date:lines:message-id:references :mime-version:user-agent:in-reply-to: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=ILfQDWhFmB7GZzItmH3YCCY/dZ7gK4iP/5FnNcsHnAE=; b=Y9Yw7X7lZYd+sphtAOsmfeFiwZohQOD8NsNIc6Xc6FVSYEHatTQ06HjLZHGJIGxH4c Ibjeqc5x/OST+jpRylUnaBM5owsr9F3y2ewS07xiNQVXuOuCQ7R2uMt6NKXmVDFxkIJX RrxnThmV8yBt8zS/6yttyGYaKF3aSCNVKUNPM3f4QmuoDfAS8bqAZUHDAtgrQzcOqkYI nYHFMYiOfJTMpFUIDPZbZd+h2uAlUNReR6mMYVZuehkuxSNEihhEXr+9ShNko8HoJqgU 4WyhG2IxlkwFeXe4DX4TBCQ4bHqcpmhDbY6L1Qm7a1cKIpYuz3Z8MhTDs22FEgGzGdqp picA== X-Gm-Message-State: ALoCoQm9ptLT/02spqdgLHxsO3tX0xRRwuvRIbtckeiF1SMcU9ai3rK7uWbUWSiHE38/ghqHfSwG X-Received: by 10.152.4.165 with SMTP id l5mr6773lal.4.1414003453691; Wed, 22 Oct 2014 11:44:13 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.152.43.200 with SMTP id y8ls231451lal.93.gmail; Wed, 22 Oct 2014 11:44:12 -0700 (PDT) X-Received: by 10.112.28.103 with SMTP id a7mr38536lbh.8.1414003452269; Wed, 22 Oct 2014 11:44:12 -0700 (PDT) Original-Received: from plane.gmane.org (plane.gmane.org. [80.91.229.3]) by mx.google.com with ESMTPS id na4si24455168lbb.65.2014.10.22.11.44.12 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 22 Oct 2014 11:44:12 -0700 (PDT) Received-SPF: pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) client-ip=80.91.229.3; Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1Xh0tH-00065t-IW for std-proposals@isocpp.org; Wed, 22 Oct 2014 20:44:11 +0200 Original-Received: from c193-14-6-157.cust.tele2.se ([193.14.6.157]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 22 Oct 2014 20:44:11 +0200 Original-Received: from bop by c193-14-6-157.cust.tele2.se with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 22 Oct 2014 20:44:11 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 37 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: c193-14-6-157.cust.tele2.se User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 In-Reply-To: X-Original-Sender: gclcip-std-proposals@m.gmane.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) smtp.mail=gclcip-std-proposals@m.gmane.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:14135 Archived-At: On 2014-10-22 20:38, Olaf van der Spek wrote: > On Wed, Oct 22, 2014 at 8:29 PM, Bo Persson wrote: >>> Is it really that difficult? >>> If the name doesn't match an already seen file but the size does one >>> could hash the contents and check the hash. >>> >> >> It really IS that difficult. >> >> On my work computer I have mounts to several departmental servers (located >> in different cities), some NAS devices that I don't even know where they >> are, a ClearCase system on a Unix machine, and the file system on a z/OS >> mainframe. Add a local hard disk, a DVD and some USB-devices, and you get a >> real world system. >> >> How is the standard supposed to specify what a unique file means? > > See above > >> And how >> useful is it for every existing compiler to support this? > > Quite useful, nearly 99.99% of the headers probably need an include > guard or something better. > One advantage of an include guard is that YOU can fix the conflicts you run into. If the compiler's #pragma once fails to include a file, what do you do about that? And should the standard require all compiler developers to have a mainframe in their test environment, so I can be sure that the pragma works on my system? Bo Persson -- --- 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. 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