220 26366 article Path: news.gmane.org!not-for-mail From: =?UTF-8?Q?Daniel_Kr=C3=BCgler?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Swapping with volatile lvalues Date: Tue, 21 Jun 2016 12:18:05 +0200 Lines: 32 Approved: news@gmane.org Message-ID: References: <81998cb5-722e-49a1-be98-7ca1e219b72a@isocpp.org> <9608d5c4-e60f-449e-9078-f27fed1f79fd@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 X-Trace: ger.gmane.org 1466504326 6902 80.91.229.3 (21 Jun 2016 10:18:46 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 21 Jun 2016 10:18:46 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCT7RVFA4QORBX5IUS5QKGQEIYXCCBA@isocpp.org Tue Jun 21 12:18:41 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f72.google.com ([209.85.215.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1bFIl3-0003ea-Bw for gclcip-std-proposals@m.gmane.org; Tue, 21 Jun 2016 12:18:13 +0200 Original-Received: by mail-lf0-f72.google.com with SMTP id l184sf8667621lfl.3 for ; Tue, 21 Jun 2016 03:18:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=0WW0fcErFaKFl/ZvHfYdjdqG2OGHPeGMD/zQoNtazE8=; b=RHl31gxn7T+nMMl9b2dlGMvpSEhVWrQ5CiZCA0S6POrkFPsV89FT7GZKtvaSnl9888 5raj1wHlcUNPH4BGl5vwY2nmBFcqgeefmVqA4qd+trdV6Jq7gX3t08kPfk0yUOupBSe0 w5EDEnq6qYssWvHqJqK+waun7gEkNnbR9h+5d3KWgy6amgp6A51oDrA59FZAzDEA/Jed 58jkH4H/LZ0Xay9z0kPplmF07IUHql547N3DTVVYapYVqjD5I0DVFdcVvBuPeNF1aLZz ytHtpBw9yLi2uJYEPxj5Zc1DUq6xGs4Zse4P27Cm23khg11sFsUJhu3xPY2YdzMnSlSa HmPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=0WW0fcErFaKFl/ZvHfYdjdqG2OGHPeGMD/zQoNtazE8=; b=b4FYwbYJTaTR1ltHSPmKFRke6dKlc3qVhP3z1oAOtZSfPWCQ83Vr2yP7NnlHR/HUaG AYOdF9hApesgYeItHMCxQRRHID1+RE/fOEgRxXatmQk/0rcyC9rhMj6hfAme47Fgok86 uXWxzQMdBXxpINirRVqvz0vaOP6DEHHp3qnG5hnYGwi4dTpQVbLoQvO+ly2JIsGkqz9q h4F607Ccwo+juKemN773dfNYNfjVAthPDyS4AfVP4gnHr/FlOQcydMnbUY8qZbN53fzA UfI3m6DRPkxiWR1gu5R9U9++YJsZOW1n08ZK1ROQkGMhJKK7ffiN/rl3HDA+4aPg6QEa x8xw== X-Gm-Message-State: ALyK8tJ5jIH+dFlOPsRl2vPOupXvRDgrkS/mpfimHmnH0UMdRhUpfJ68sfECmq73xw3lMA== X-Received: by 10.28.154.147 with SMTP id c141mr421893wme.2.1466504287894; Tue, 21 Jun 2016 03:18:07 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.46.71.147 with SMTP id u141ls305062lja.109.gmail; Tue, 21 Jun 2016 03:18:06 -0700 (PDT) X-Received: by 10.25.22.70 with SMTP id m67mr4753693lfi.25.1466504286604; Tue, 21 Jun 2016 03:18:06 -0700 (PDT) Original-Received: from mail-lb0-x22e.google.com (mail-lb0-x22e.google.com. [2a00:1450:4010:c04::22e]) by mx.google.com with ESMTPS id e63si29485824lfb.285.2016.06.21.03.18.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Jun 2016 03:18:06 -0700 (PDT) Received-SPF: pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:4010:c04::22e as permitted sender) client-ip=2a00:1450:4010:c04::22e; Original-Received: by mail-lb0-x22e.google.com with SMTP id o4so7600529lbp.2 for ; Tue, 21 Jun 2016 03:18:06 -0700 (PDT) X-Received: by 10.195.10.131 with SMTP id ea3mr17960448wjd.86.1466504285936; Tue, 21 Jun 2016 03:18:05 -0700 (PDT) Original-Received: by 10.28.168.148 with HTTP; Tue, 21 Jun 2016 03:18:05 -0700 (PDT) In-Reply-To: <9608d5c4-e60f-449e-9078-f27fed1f79fd@isocpp.org> X-Original-Sender: daniel.kruegler@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of daniel.kruegler@gmail.com designates 2a00:1450:4010:c04::22e as permitted sender) smtp.mailfrom=daniel.kruegler@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-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:26366 Archived-At: 2016-06-21 12:12 GMT+02:00 FrankHB1989 : > Call of std::exchange can work, but it seems not so ideal. This is a misunderstanding of my possibly ambiguous response. I didn't mean to use std::exchange, but instead I was trying to suggest that if you were considering to reuse an existing name it should better be exchange instead of swap. > The return type > of std::exchange is template parameter type T, so when T is a volatile type, > lvalue-to-rvalue conversion would be performed, and there are likely more > side effects than needed. > I also don't think using the volatile lvalue return value (which is not the > case for std::exchange) a good idea. Discarded-value expressions can work in > such cases, but is seems to be strange and too error-prone. So perhaps the > return type of the call should be void. > Regarding with Swappable requriements and symmetry... how about providing 2 > overloading? I still feel uneasy about it, especially when trying to make a consistent sense with your suggested overloads (even assuming that both overloads would be provided) and the Swappable post-conditions. But again, I haven't thought carefully through it. - Daniel -- 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/CAGNvRgCYLywvtFSO65-NKpeycpT4cPnw0SjvQPhE_DRL98UO7g%40mail.gmail.com. .