220 17715 <32925383-d00e-4e1d-81df-2516c2ccaa6f@isocpp.org> article Path: news.gmane.org!not-for-mail From: Edward Catmur Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: =?UTF-8?Q?=5Bstd=2Dproposals=5D_Re=3A_Proposal=3A_Class_static_=E2=80=9Cproper?= =?UTF-8?Q?ty=E2=80=9D_constants_in_vtables?= Date: Tue, 5 May 2015 23:49:07 -0700 (PDT) Lines: 39 Approved: news@gmane.org Message-ID: <32925383-d00e-4e1d-81df-2516c2ccaa6f@isocpp.org> References: <49c358a2-d19a-415f-a4fa-1ff67286a0ad@isocpp.org> <8ac58c5d-6542-43ff-b42c-b58cbf16be6d@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_5604_154822941.1430894947748" X-Trace: ger.gmane.org 1430894952 12202 80.91.229.3 (6 May 2015 06:49:12 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 6 May 2015 06:49:12 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDZLZTXF7UJBBZHSU2VAKGQE4BDXIJY@isocpp.org Wed May 06 08:49:11 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f71.google.com ([209.85.220.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Ypt8o-0006Z1-Hi for gclcip-std-proposals@m.gmane.org; Wed, 06 May 2015 08:49:10 +0200 Original-Received: by pabvw2 with SMTP id vw2sf1359522pab.2 for ; Tue, 05 May 2015 23:49:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:content-type:x-original-sender:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=4vcvMHGf+vWNRyldrpwJytbVy4SkIRCZqsDNj4ethNg=; b=Ykvy7Sxv4456ckb31xsRJxd5oDFoY8PLpLMQgW86e/dxbGE7njcle7/ORUWbHHct/L Oh7oYRLPCL2/Ij4BiqgOpbE9bRPseTW8eChRp9p3wFl27LA9i+nk/2McmXGV9NU/241O 8kdxAdiNekbty5CXfsDneXrlWn8HVmlkLo8Nw0Ej384MWMcQbD1V9QiTpIyEPc59g5ta gsRSn3scb0h19zu8vsEULKggXKmC9cc4t3Lqr3l29hNeYQyP0pCNSKEPb3+dJT4oZIV4 TwnQhKzfQ4llUG3BB3fYYnIza8TnV4hK4cfDG84FAhcjkrE2QzUIS9BExevwDsW0D23a jvmw== X-Gm-Message-State: ALoCoQkqvTvJUb1IIB/A3OswMiRAVhWJ/lYO73Rg3k1UjpM3sgu9B7jsX3G5qCVsXn4e86It/0gi X-Received: by 10.68.211.230 with SMTP id nf6mr2986654pbc.10.1430894949475; Tue, 05 May 2015 23:49:09 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.87.69 with SMTP id q63ls5516qgd.90.gmail; Tue, 05 May 2015 23:49:08 -0700 (PDT) X-Received: by 10.140.93.226 with SMTP id d89mr338524qge.38.1430894948703; Tue, 05 May 2015 23:49:08 -0700 (PDT) In-Reply-To: X-Original-Sender: ed@catmur.co.uk 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:17715 Archived-At: ------=_Part_5604_154822941.1430894947748 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable The term "attribute" is [[already_taken]]. Call these what they are: virtua= l static data members.=20 I would also suggest collecting some performance measurements to back up yo= ur argument (eg with a hand-rolled vtable implementation). You should also = make it clear that you understand that the C++ standard does not mandate vt= ables as an implementation technique although of course in practice every i= mplementation uses them.=20 Would this mean that pointers to data members can now involve a vtable look= up? Could that break ABI?=20 I note you haven't provided definitions for the members as would usually be= required for static data members. Is that an omission or intentional?=20 Is it really necessary that virtual static data members be const? Non-const= virtual static data members would have to be allocated outside the vtable = itself, but access to them would still be considerably cheaper than a nulla= ry virtual method call. Note that also objects with run time initialization= would need to be allocated outside the vtable, even if they were const the= reafter.=20 --=20 ---=20 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 e= mail 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-proposa= ls/. ------=_Part_5604_154822941.1430894947748-- .