220 7394 article Path: news.gmane.org!not-for-mail From: =?ISO-8859-1?Q?Daniel_Kr=FCgler?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: std::any: Add a way to obtain a void* to the contained value. Date: Tue, 22 Oct 2013 10:15:05 +0200 Lines: 37 Approved: news@gmane.org Message-ID: References: <2542b0a1-d4db-48d8-97e3-05dd31ba569f@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 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1382429704 19491 80.91.229.3 (22 Oct 2013 08:15:04 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 22 Oct 2013 08:15:04 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCT7RVFA4QORBCXITCJQKGQENXMDK2Q@isocpp.org Tue Oct 22 10:15:09 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wg0-f70.google.com ([74.125.82.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VYX7K-0005de-Ue for gclcip-std-proposals@m.gmane.org; Tue, 22 Oct 2013 10:15:06 +0200 Original-Received: by mail-wg0-f70.google.com with SMTP id c11sf9684642wgh.9 for ; Tue, 22 Oct 2013 01:15:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=mime-version:in-reply-to:references:date:message-id:subject:from: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 :content-transfer-encoding; bh=nQ2THk65WdxIaAeL9hD7VT6SKlwCfd739aZuzaYvP/I=; b=ZW/tFuWUb2uRezewatUcsH9oifuqxo/Ao7Sdj/F6bUVJilnrznW7t4/vpUzBp6E7ch 9JVTvvw7w88hYbJonEf/5uL5cLAE62bQULmNmUDjwUthZqS59ddGzKfV5YoxeKYNkV57 ejhMNI2TbwTIa9wFXq8Z3p8GnD97XO4tHitvU2u/ZPfOFaWiL8mZb2F4bSPQnu+JBxK0 faMrtvSiDAUvhUSDNDqKI5Yw96fMp3h0ifMb66DdaasKXF+xufrD4YdpqKq04unbOEYt uY8ota28aaMFTEN5CLPG+339vajgh4uPoKFait2DJ+2k3JZZBm/J6cdL1AkdrDepS91a uFtw== X-Received: by 10.181.11.165 with SMTP id ej5mr6579379wid.0.1382429706298; Tue, 22 Oct 2013 01:15:06 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.86.73 with SMTP id n9ls598265wiz.34.canary; Tue, 22 Oct 2013 01:15:05 -0700 (PDT) X-Received: by 10.180.89.42 with SMTP id bl10mr13025608wib.47.1382429705823; Tue, 22 Oct 2013 01:15:05 -0700 (PDT) Original-Received: from mail-wg0-x22b.google.com (mail-wg0-x22b.google.com [2a00:1450:400c:c00::22b]) by mx.google.com with ESMTPS id vu5si1515387wjc.7.2013.10.22.01.15.05 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 22 Oct 2013 01:15:05 -0700 (PDT) Received-SPF: pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c00::22b as permitted sender) client-ip=2a00:1450:400c:c00::22b; Original-Received: by mail-wg0-f43.google.com with SMTP id b13so7527360wgh.34 for ; Tue, 22 Oct 2013 01:15:05 -0700 (PDT) X-Received: by 10.180.101.197 with SMTP id fi5mr13401451wib.46.1382429705726; Tue, 22 Oct 2013 01:15:05 -0700 (PDT) Original-Received: by 10.216.169.71 with HTTP; Tue, 22 Oct 2013 01:15:05 -0700 (PDT) In-Reply-To: X-Original-Sender: daniel.kruegler@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:400c:c00::22b as permitted sender) smtp.mail=daniel.kruegler@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com 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:7394 Archived-At: 2013/10/22 Daniel Kr=FCgler : > 2013/10/22 : >> Here's the code of unsafe_any_cast: >> >> template >> inline ValueType * unsafe_any_cast(any * operand) BOOST_NOEXCEPT >> { >> return &static_cast >> *>(operand->content)->held; >> } >> >> If I instantiate this template, I get a static_cast*>= .. >> This is UB. > > Please look at the suggestion from the view-point of an API > suggestion, not by looking into the code. It all depends what the > specification would be and a library internal can decide how to > realize that. If the specification says that you can query for void*, > it needs to work - regardless of the internal way how to do that. That being said I agree that unsafe_any_cast is not what you have been asking for. > - Daniel --=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/. .