220 37353 <2555999.PcE7Su909f@tjmaciei-mobl1> article Path: news.gmane.org!.POSTED!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: `offsetof` in a macro-less, modular world Date: Thu, 15 Mar 2018 20:37:49 -0700 Lines: 32 Approved: news@gmane.org Message-ID: <2555999.PcE7Su909f@tjmaciei-mobl1> References: <2319008.6H3YVR8kxN@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Trace: blaine.gmane.org 1521171390 19016 195.159.176.226 (16 Mar 2018 03:36:30 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 16 Mar 2018 03:36:30 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBN7YVTKQKGQE5N7RJEY@isocpp.org Fri Mar 16 04:36:25 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f197.google.com ([209.85.220.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ewgAK-0004tS-TB for gclcip-std-proposals@m.gmane.org; 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[2001:19f0:5:2221::1:3]) by mx.google.com with ESMTPS id p24si3041211qkp.80.2018.03.15.20.38.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 15 Mar 2018 20:38:30 -0700 (PDT) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 2001:19f0:5:2221::1:3 as permitted sender) client-ip=2001:19f0:5:2221::1:3; Original-Received: from tjmaciei-mobl1.localnet (unknown [IPv6:2601:1c0:4501:5f9f:cdd9:d8c0:f4a1:41bc]) by smtp.macieira.info (Postfix) with ESMTPSA id 50687A67B for ; Thu, 15 Mar 2018 20:38:29 -0700 (PDT) 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 2001:19f0:5:2221::1:3 as permitted sender) smtp.mailfrom=thiago@macieira.org Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org 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:37353 Archived-At: On Thursday, 15 March 2018 18:05:52 PDT Andrey Semashev wrote: > > Why not? We can if we give ourselves the syntax for it. > > Well, we don't have one now, that's why you can't do that. We need at > least a proposal for this new syntax to have a meaningful comparison > with offsetof. Right. I'm just saying that we should use pointer-to-members instead, since they would also give us type safety, something that offsetof can't do. > > int A:: *int_in_A = &A::y; // just so we don't discuss arrays just now > > A B:: *A_in_B = &B::a; > > int B:: *int_in_B = int_in_A + A_in_B; // syntax TBD > > Right, that illustrates what I called "much more difficult". offsetof is > pretty difficult to beat in code conciseness and clarity. But you get an offset, which breaks a lot of assumptions in the type system. It's not really easy to use. -- Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/2555999.PcE7Su909f%40tjmaciei-mobl1. .