220 29877 <20161217171633.4919375.58072.21574@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: New smart pointer: CopyConstructible and CopyAssignable flavor of unique_ptr Date: Sat, 17 Dec 2016 12:16:33 -0500 Lines: 71 Approved: news@gmane.org Message-ID: <20161217171633.4919375.58072.21574@gmail.com> References: <67a9e9ed-8748-4098-a43b-33598b516464@isocpp.org> <20161217141109.GA22645@manuel-ThinkPad-L440.localdomain> <3df7e8eb-01a0-7804-f476-504b5a25a9fe@gmail.com> <20161217170428.GA10214@manuel-ThinkPad-L440.localdomain> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1481994998 5117 195.159.176.226 (17 Dec 2016 17:16:38 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 17 Dec 2016 17:16:38 +0000 (UTC) To: Manuel Bergler , std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUZ5QWKNQIPHZOVYICRUBE2OQ72M@isocpp.org Sat Dec 17 18:16:32 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f198.google.com ([209.85.161.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cIIb2-0000Qt-BF for gclcip-std-proposals@m.gmane.org; Sat, 17 Dec 2016 18:16:32 +0100 Original-Received: by mail-yw0-f198.google.com with SMTP id l139sf93795012ywe.5 for ; Sat, 17 Dec 2016 09:16:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:content-transfer-encoding:message-id:date:subject:from :in-reply-to:references: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=zpvqrYqO9MZF54ihgHgONWXRCCB45utjTJsbrvSOTdo=; b=CK+kZdZYzy65+AvQs4K09aRVHPGELM/CDc/wZmMETcDyXMydsGCDkIi1IwM2hYyGRk lwDSlJjHtOA7WsCitGaosaNGH8ghPbsvFH1sYYGTVU+sUjV9h8D2vTAlmTXLh3xDi4dp OlTycVMhSuHGiWonaaHATJsQGVNlOetOQB8xilKwJFxeoRZO2cJbTC4dO3UwJjMu96dE 2xbo9XGYJLXaE3D5aynpQnnQaee84tmQSE7KTdORRDN2BYLN7McBrUMHD1q8jPyBJb2j 9UwMaY5nhJUfTOYBoBcooWpKKG4RLhHN+bk6rJbqHSErpsurdax04zOFvIiaU3POyU/S cYkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:content-transfer-encoding :message-id:date:subject:from:in-reply-to:references: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=zpvqrYqO9MZF54ihgHgONWXRCCB45utjTJsbrvSOTdo=; b=qP46AqDXfz+ZWW+GHJ5mkd4jVcZiEpX5nUibYoF3mKFi8s5aWjQDvG3+SeWaYQQ6Yc tq6R9mHDd6plnwCzuD4jrlvzb8x7Mex3oBtGiUemFaAxtJ+0povH6APrQUMwO/SP2W9y LuEN/Z6g6tr4+eKxTGiKe10XZjCYEmHlyreOCy+hPiYjb4a902PPFoK7frVQ32UmQ3Ag yIv3OnKJR07Mfnnxz10h3rHleWPMgyxaR2CExzpzdKntgRpN1teoAHg0LnDibBSr8BlX uzyPyVwjiVrGdjdWh4wBex242o+EIDPfknHUYsbCk9LciPP+TppWeSEULLjtCWS/Il5i Z3+ X-Gm-Message-State: AKaTC01eg+mKZgWdg2c0bhYDgHGkfqFTRjPKueDPJBLsDe+CFtLyI0KvKSaruDHnAsRUTQ== X-Received: by 10.13.237.5 with SMTP id w5mr1948205ywe.21.1481994996448; Sat, 17 Dec 2016 09:16:36 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.130.7 with SMTP id t7ls1269024itd.20.canary-gmail; Sat, 17 Dec 2016 09:16:35 -0800 (PST) X-Received: by 10.36.204.9 with SMTP id x9mr9710051itf.123.1481994995356; Sat, 17 Dec 2016 09:16:35 -0800 (PST) Original-Received: from mail-io0-x241.google.com (mail-io0-x241.google.com. [2607:f8b0:4001:c06::241]) by mx.google.com with ESMTPS id u186si6148424itf.113.2016.12.17.09.16.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 17 Dec 2016 09:16:35 -0800 (PST) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 2607:f8b0:4001:c06::241 as permitted sender) client-ip=2607:f8b0:4001:c06::241; Original-Received: by mail-io0-x241.google.com with SMTP id b194so15052587ioa.3 for ; Sat, 17 Dec 2016 09:16:35 -0800 (PST) X-Received: by 10.107.133.76 with SMTP id h73mr9668815iod.148.1481994994812; Sat, 17 Dec 2016 09:16:34 -0800 (PST) Original-Received: from [127.0.0.1] ([74.15.44.73]) by smtp.gmail.com with ESMTPSA id d25sm2008815ioj.30.2016.12.17.09.16.33 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Sat, 17 Dec 2016 09:16:33 -0800 (PST) X-Mailer: BlackBerry Email (10.3.2.2876) In-Reply-To: <20161217170428.GA10214@manuel-ThinkPad-L440.localdomain> X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2607:f8b0:4001:c06::241 as permitted sender) smtp.mailfrom=tvaneerd@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:29877 Archived-At: =E2=80=8E>=C2=A0I might miss something here, but I can't think of a use-cas= e where the convenience of returning it from a function by value having it = implicitly clone the pointee with `return my_clone_ptr;` instead of just wr= iting `return my_clone_ptr.clone();` Templates. Where you don't know if T has .clone(). Cloning in C++ is typica= lly spelled with the copy-constructor.=C2=A0 Sent=C2=A0from=C2=A0my=C2=A0BlackBerry=C2=A0portable=C2=A0Babbage=C2=A0Devi= ce =C2=A0 Original Message =C2=A0 From: Manuel Bergler Sent: Saturday, December 17, 2016 12:05 PM To: std-proposals@isocpp.org Reply To: std-proposals@isocpp.org Subject: Re: [std-proposals] New smart pointer: CopyConstructible and CopyA= ssignable flavor of unique_ptr On Sat, Dec 17, 2016 at 06:10:10PM +0200, Ville Voutilainen wrote: >On 17 December 2016 at 17:35, Jonathan M=C3=BCller > wrote: >> On 17.12.2016 16:29, Ville Voutilainen wrote: >>> >>> Such a type has just one problem: it's close to useless. It doesn't >>> violate Sean's lofty principles, >>> but it doesn't solve the problems it's aimed for either. >> >> >> What are the problems it's aimed for exactly? > > >Convenient cloning, and automatic cloning when passed by value or >returned by value, including when >wrapped under something else as a member. Needing to manually invoke a >clone function more or less >completely defeats that purpose. > I might miss something here, but I can't think of a use-case where the conv= enience of returning it from a function by value having it implicitly clone= the pointee with `return my_clone_ptr;` instead of just writing `return my= _clone_ptr.clone();` is worth sacrificing the clarity of the latter version= , in particular since you might actually have intended to move it but forgo= t to call `std::move` on it before returning. So as far as I can tell the only remaining benefit is that you needn't writ= e a custom copy/move constructor/assignment operator for a struct/class hav= ing one of these as a member? --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/20161217170428.GA10214%40manuel-ThinkPad-L440.lo= caldomain. --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/20161217171633.4919375.58072.21574%40gmail.com. .