From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gproxy1-pub.mail.unifiedlayer.com (gproxy1-pub.mail.unifiedlayer.com [69.89.25.95]) by sourceware.org (Postfix) with ESMTPS id 385E83952495 for ; Mon, 5 Dec 2022 21:41:40 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 385E83952495 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=tromey.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tromey.com Received: from cmgw12.mail.unifiedlayer.com (unknown [10.0.90.127]) by progateway3.mail.pro1.eigbox.com (Postfix) with ESMTP id 7C3C710045A03 for ; Mon, 5 Dec 2022 21:41:28 +0000 (UTC) Received: from box5379.bluehost.com ([162.241.216.53]) by cmsmtp with ESMTP id 2JDMpEgv713QT2JDMpq349; Mon, 05 Dec 2022 21:41:28 +0000 X-Authority-Reason: nr=8 X-Authority-Analysis: v=2.4 cv=a9v1SWeF c=1 sm=1 tr=0 ts=638e6588 a=ApxJNpeYhEAb1aAlGBBbmA==:117 a=ApxJNpeYhEAb1aAlGBBbmA==:17 a=dLZJa+xiwSxG16/P+YVxDGlgEgI=:19 a=sHyYjHe8cH0A:10:nop_rcvd_month_year a=Qbun_eYptAEA:10:endurance_base64_authed_username_1 a=CCpqsmhAAAAA:8 a=1wzFVzZa57Hvl5fhFlkA:9 a=ul9cdbp4aOFLsgKbc677:22 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tromey.com; s=default; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date:References :Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=+fo/1/GJLSjdqyq9rhrE6clq3/yELRqCSt7ZhB+YknE=; b=rxtp8ClQGvta2MLFzu6+abUGbu /w56DDeQTiv1h6edO8Ks6axKqpMmYWsRXSE+JHxgAPFFqHQfRXglXdipJ9hKe8tGmrtMyqFlimSOF kuoYhRKS/TnPJsW+3Gjpt2Wyw; Received: from 97-122-76-186.hlrn.qwest.net ([97.122.76.186]:56938 helo=murgatroyd) by box5379.bluehost.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1p2JDL-003ntl-UQ; Mon, 05 Dec 2022 14:41:27 -0700 From: Tom Tromey To: Simon Marchi via Gdb-patches Cc: Simon Marchi Subject: Re: [PATCH 4/6] gdb: revert frame_unwind::this_id and callees to use `frame_info *` References: <20221202180052.212745-1-simon.marchi@polymtl.ca> <20221202180052.212745-5-simon.marchi@polymtl.ca> X-Attribution: Tom Date: Mon, 05 Dec 2022 14:41:26 -0700 In-Reply-To: <20221202180052.212745-5-simon.marchi@polymtl.ca> (Simon Marchi via Gdb-patches's message of "Fri, 2 Dec 2022 13:00:50 -0500") Message-ID: <87cz8xjzp5.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - box5379.bluehost.com X-AntiAbuse: Original Domain - sourceware.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tromey.com X-BWhitelist: no X-Source-IP: 97.122.76.186 X-Source-L: No X-Exim-ID: 1p2JDL-003ntl-UQ X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 97-122-76-186.hlrn.qwest.net (murgatroyd) [97.122.76.186]:56938 X-Source-Auth: tom+tromey.com X-Email-Count: 1 X-Source-Cap: ZWx5bnJvYmk7ZWx5bnJvYmk7Ym94NTM3OS5ibHVlaG9zdC5jb20= X-Local-Domain: yes X-Spam-Status: No, score=-3022.2 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,JMQ_SPF_NEUTRAL,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: >>>>> "Simon" == Simon Marchi via Gdb-patches writes: Simon> So, this patch started out as changing the prototype of Simon> frame_unwind::this_id and adjusting callees recursively until the code Simon> compiled again. Simon> The question is: doesn't this defeat the purpose of frame_info_ptr? I Simon> think it depends on what we decide the purpose of frame_info_ptr is. Simon> 1. catch accesses to stale frame_info ptr (and assert if so) Simon> 2. reinflate frame_info objects automatically. Simon> Right now, it does #1. My goal is to make it to #2. I think that is Simon> more in line with the original "reinflatable frames" idea, and in Simon> general more useful. To be clear, my goal in doing this was to try to eliminate the bug where a frame_info pointer is held across a frame cache reinit. From my perspective, both of these approaches satisfy that goal, so the idea of this change seems completely fine. Simon> And since those frames whose id is being computed Simon> are by definition not reinflatable (you need to id to reinflate), it's Simon> not really useful to have frame_info_ptr on code paths that deal with Simon> frames whose id is currently being computed. Reinflation only really Simon> makes sense for the "users" of the frame API, those who receive a frame Simon> with a computed id. And by experience, this is where the "using stale Simon> frame_info" bugs happen, a user holding a frame_info across a target Simon> resumption. Basically I looked into this and it seemed difficult, so I gave up. And, a simpler approach didn't work. But, you managed it :-) So kudos! I think a good long run goal would be if frame_id and frame_info_ptr were generally merged. That is, the "using" code should only ever need to touch a frame_info_ptr. I don't know if this is really feasible, but it would be another step toward making the API simpler to use and less buggy. Simon> Now, we could have two separate class frame_info wrapper classes, one Simon> that is today's frame_info_ptr, whose goal is just to catch uses of Simon> stale frame_info objects, and one that is the one at the end of this Simon> series, whose goal is to do automatic reinflation. I would say the default choice should be a single class, unless for some reason it's too expensive. Tom