From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 128698 invoked by alias); 15 Nov 2016 20:22:14 -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 128000 invoked by uid 89); 15 Nov 2016 20:22:13 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.7 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 15 Nov 2016 20:22:12 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 20165624B3 for ; Tue, 15 Nov 2016 20:22:11 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-204-29.brq.redhat.com [10.40.204.29]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uAFKM9Fv015459 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 15 Nov 2016 15:22:10 -0500 Subject: Re: Use of mcheck during GDB development To: Pedro Alves , gdb-patches@sourceware.org References: From: Florian Weimer Message-ID: Date: Tue, 15 Nov 2016 20:22:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-11/txt/msg00396.txt.bz2 On 11/15/2016 09:03 PM, Pedro Alves wrote: > On 11/15/2016 04:00 PM, Florian Weimer wrote: >> We need to get rid of the mcheck functionality in glibc because we >> really, really want to stop calling the malloc hook functions. >> >> A future glibc version will provide a lightweight heap checker, with >> functionality comparable to mcheck (but thread-safe!) as linkable and >> LD_PRELOAD-able (perhaps under a different name than libmcheck). >> >> How critical is the mcheck functionality to GDB development? > > Despite its flaws, it catches bugs. It's lightweight enough that > it can be on all the time. It's nice to have, IMO. Interesting. Do you know which mcheck bits actually catch failures? >> Would it >> be a problem if next glibc release would issue a deprecation warning >> without actually having a suitable replacement in-tree? > > Will that cause build problems with -Werror? I don't know. As far as I can tell, you just link with -lmcheck. This should give you at most a link-time warning, which wouldn't fail the build. >> I want to get the deprecation notice out as soon as possible, but I >> might not be able to finish the mcheck replacement in time for the next >> glibc release. > > If there's no replacement that users can move to, what's the point > of warning soon? Is there an advantage vs only when the replacement > exists? We can incorporate feedback from existing users into the design of the replacement. We wouldn't be having this conversation if I didn't announce my intent to deprecate without immediate replacement from the glibc side. I think most people use valgrind for memory debugging. Thanks, Florian