From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 111815 invoked by alias); 1 Oct 2016 04:23:37 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 111741 invoked by uid 89); 1 Oct 2016 04:23:36 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.4 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,RCVD_IN_SORBS_SPAM,SPF_PASS autolearn=no version=3.3.2 spammy=spoke, Though, super X-HELO: gproxy6-pub.mail.unifiedlayer.com Received: from gproxy6-pub.mail.unifiedlayer.com (HELO gproxy6-pub.mail.unifiedlayer.com) (67.222.39.168) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with SMTP; Sat, 01 Oct 2016 04:23:26 +0000 Received: (qmail 14728 invoked by uid 0); 1 Oct 2016 04:23:25 -0000 Received: from unknown (HELO cmgw2) (10.0.90.83) by gproxy6.mail.unifiedlayer.com with SMTP; 1 Oct 2016 04:23:25 -0000 Received: from box522.bluehost.com ([74.220.219.122]) by cmgw2 with id q4PL1t00L2f2jeq014PPSQ; Fri, 30 Sep 2016 22:23:23 -0600 X-Authority-Analysis: v=2.1 cv=KuvehwmN c=1 sm=1 tr=0 a=GsOEXm/OWkKvwdLVJsfwcA==:117 a=GsOEXm/OWkKvwdLVJsfwcA==:17 a=L9H7d07YOLsA:10 a=9cW_t1CCXrUA:10 a=s5jvgZ67dGcA:10 a=GW1xBdLrtEIA:10 a=cAjaPd0IYssQXaei55YA:9 Received: from 71-218-192-86.hlrn.qwest.net ([71.218.192.86]:39606 helo=bapiya) by box522.bluehost.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.86_1) (envelope-from ) id 1bqBpZ-0005YO-Tf; Fri, 30 Sep 2016 22:23:22 -0600 From: Tom Tromey To: Tom Tromey Cc: Pedro Alves , Trevor Saunders , gdb-patches@sourceware.org Subject: Re: [RFA 02/22] Use RAII to save and restore scalars References: <1474949330-4307-1-git-send-email-tom@tromey.com> <1474949330-4307-3-git-send-email-tom@tromey.com> <20160927085937.com7c7ct4wuchzpg@ball> <87wphtfmcj.fsf@tromey.com> <579b45a0-2393-bda9-a244-cb2f7611635f@redhat.com> <87k2dsg1ul.fsf@tromey.com> Date: Sat, 01 Oct 2016 04:23:00 -0000 In-Reply-To: <87k2dsg1ul.fsf@tromey.com> (Tom Tromey's message of "Fri, 30 Sep 2016 21:55:14 -0600") Message-ID: <87fuogg0jr.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-BWhitelist: no X-Exim-ID: 1bqBpZ-0005YO-Tf X-Source-Sender: 71-218-192-86.hlrn.qwest.net (bapiya) [71.218.192.86]:39606 X-Source-Auth: tom+tromey.com X-Email-Count: 3 X-Source-Cap: ZWx5bnJvYmk7ZWx5bnJvYmk7Ym94NTIyLmJsdWVob3N0LmNvbQ== X-SW-Source: 2016-10/txt/msg00002.txt.bz2 Pedro> Guess we could have the copy constructor actually move instead of Pedro> copy, setting the copied-from's pointer member to NULL, and then Pedro> have the destructor do nothing if the pointer is NULL. Tom> Yeah. I took this approach. I'm not super thrilled with it, but at the Tom> same time it's not *too* bad. Scratch that, I spoke too soon. I couldn't get this to work. I don't understand why the 2-argument form of make_scoped_restore requires a copy constructor while the 1-argument form does not. However, once you need a copy constructor, it doesn't seem possible without a move constructor. The issue is that a copy constructor take a const reference, so you can't modify the fields of the original. Removing the 2-argument form seems to work. Though like I said, I don't know why. Also, as an aside, I found I was using nullptr in my patches, but this isn't C++03. I think -std=c++03 is going to be needed or else it will be too easy to slip in C++11-isms. Now, I do think C++11 is really much better, but my understanding is that C++03 is what gdb decided on. Tom