220 20546 <6D75256B-F476-4BA4-BA13-D2342F8B7B6B@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Draft D0065: Movable initializer lists, rev. 2 Date: Mon, 21 Sep 2015 14:25:51 +0800 Lines: 95 Approved: news@gmane.org Message-ID: <6D75256B-F476-4BA4-BA13-D2342F8B7B6B@gmail.com> References: <87343e65-eecd-4b96-86b7-a883aa7f9d1d@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_36507162-5AD5-431B-BFDF-1350E26C4CC4" X-Trace: ger.gmane.org 1442816782 10707 80.91.229.3 (21 Sep 2015 06:26:22 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 21 Sep 2015 06:26:22 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBBWG72XQKGQEC6J6IBQ@isocpp.org Mon Sep 21 08:26:16 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ig0-f197.google.com ([209.85.213.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZduYK-0008V8-7l for gclcip-std-proposals@m.gmane.org; Mon, 21 Sep 2015 08:26:16 +0200 Original-Received: by igbgg5 with SMTP id gg5sf176206207igb.1 for ; Sun, 20 Sep 2015 23:26:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:content-type:message-id:mime-version :subject:date:references:to:in-reply-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=m6gyXcOAKQCqCGWlisncTp2oKAmsfVl8KDfZ9vDwzos=; b=Uvr4OEv5W6silbkL7fdJxi4kdfkfwwitGIUcZ3fRd3WQUHjbbczESEAy69/OIa0136 wAG08RfX+sefA5NbecQqaxUZ4y+XUtqlMGKzbQt60L3Z8xMSDPQejycq4uOjt0tw2uSx 5R7BNCuoqg5CpJuopPfbzcFq6ntWtL7JyPBQhKvxYLKHGlILwbv3kAX/X+Jv3HKWNmsQ Jo6KIphU2r5GS/6zbSyCYwTuTWevV4pe0hsC1nYxUDaeWbLrUIqT1GAVxg0ph7NgFMjj w42jeMj1tJztQRi72cKZxTqd2L81rYCWSnrPwigN7odMClLXE4efLPVyiS3Zm3ueH1kp CIgA== X-Gm-Message-State: ALoCoQk4WL7jR5yHs8r/2+vr/LY7fBCJ4DZFY+4l5YG5hFILVw7Y+CU+/05MZXoy1/pO6hUytWal X-Received: by 10.182.213.166 with SMTP id nt6mr16687112obc.3.1442816775361; Sun, 20 Sep 2015 23:26:15 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.29.52 with SMTP id g20ls758898igh.23.gmail; Sun, 20 Sep 2015 23:26:14 -0700 (PDT) X-Received: by 10.68.185.132 with SMTP id fc4mr22646513pbc.96.1442816774598; Sun, 20 Sep 2015 23:26:14 -0700 (PDT) Original-Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com. [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id gd3si35434978pbb.75.2015.09.20.23.26.14 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 20 Sep 2015 23:26:14 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::22f as permitted sender) client-ip=2607:f8b0:400e:c03::22f; Original-Received: by pacex6 with SMTP id ex6so107654157pac.0 for ; Sun, 20 Sep 2015 23:26:14 -0700 (PDT) X-Received: by 10.68.133.13 with SMTP id oy13mr2116577pbb.125.1442816774166; Sun, 20 Sep 2015 23:26:14 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.54.46]) by smtp.gmail.com with ESMTPSA id rx8sm11758543pbb.90.2015.09.20.23.26.11 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 20 Sep 2015 23:26:13 -0700 (PDT) In-Reply-To: X-Mailer: Apple Mail (2.2104) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::22f as permitted sender) smtp.mailfrom=potswa@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-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:20546 Archived-At: --Apple-Mail=_36507162-5AD5-431B-BFDF-1350E26C4CC4 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 > On 2015=E2=80=9309=E2=80=9321, at 1:41 PM, Tomasz Kami=C5=84ski wrote: >=20 > However, I still think that removing the move-constructor would be benefi= cial. The existence of the move-constructor and the name (own_initializer_l= ist) suggest that the list object actually manages storage and moves it fro= m one object to another. As the own_initializer_list is effectively wrapped= reference to stack allocated array, it cannot do that, so the current desi= gn is misleading. Does a std::vector (or, as you mention, unique_ptr) =E2=80=9Cmove stor= age from one object to another=E2=80=9D? Aside from user-replaced ::operato= r new or watching the stack pointer, and aside from the restricted capabili= ties of the list, what=E2=80=99s the observable difference between own_init= ializer_list and unique_ptr? > What is motivation for own_initializer_list being move-able? It's existen= ce suggest user that the class behaves more like unique_ptr than refer= ence to stack array. Please see =C2=A74.4 Ownership, from the second paragraph onward. Note that a moved-from list does not destroy any sequence, even one it was = directly initialized with. --=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/. --Apple-Mail=_36507162-5AD5-431B-BFDF-1350E26C4CC4 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=UTF-8
On 2015=E2=80=9309= =E2=80=9321, at 1:41 PM, Tomasz Kami=C5=84ski <tomaszkam@gmail.com> wrote:

=
However, I still think that removing the move-co= nstructor would be beneficial. The existence of the move-constructor and th= e name (own_initializer_list) suggest that the list object actually manages= storage and moves it from one object to another. As the own_initializer_li= st is effectively wrapped reference to stack allocated array, it cannot do = that, so the current design is misleading.

Does a std::= vector (or, as you mention, unique_ptr<T[]>) =E2=80=9Cmove storage from= one object to another=E2=80=9D? Aside from user-replaced ::operator new or watching the stack pointer, and a= side from the restricted capabilities of the list, what=E2=80=99s the obser= vable difference between own_initializer_= list and unique_ptr<T[]>?

What is motivation for own_initializer= _list being move-able? It's existence suggest user that the class behaves m= ore like unique_ptr<T[]> than reference to stack array.

Please see =C2=A74.4= Ownership, from the second paragraph onward.
<= br class=3D"">
Note that a moved-from list does not destroy any s= equence, even one it was directly initialized with.

--

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