From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 79604 invoked by alias); 20 Oct 2017 15:29:04 -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 79595 invoked by uid 89); 20 Oct 2017 15:29:03 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.9 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=no 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; Fri, 20 Oct 2017 15:29:02 +0000 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9A50C4DAFB; Fri, 20 Oct 2017 15:29:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 9A50C4DAFB Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=palves@redhat.com Received: from [127.0.0.1] (ovpn04.gateway.prod.ext.ams2.redhat.com [10.39.146.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8E3FA18C56; Fri, 20 Oct 2017 15:29:00 +0000 (UTC) Subject: Re: [PATCH V4] symlookup: improves symbol lookup when a file is specified. To: Simon Marchi , "Tedeschi, Walfred" , Simon Marchi References: <1508317280-31265-1-git-send-email-walfred.tedeschi@intel.com> <327caaf3429595c07a29d455ea3ed6a0@polymtl.ca> Cc: "gdb-patches@sourceware.org" From: Pedro Alves Message-ID: Date: Fri, 20 Oct 2017 15:29:00 -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 Content-Transfer-Encoding: 7bit X-SW-Source: 2017-10/txt/msg00669.txt.bz2 On 10/20/2017 03:28 PM, Simon Marchi wrote: > On 2017-10-20 03:45 AM, Tedeschi, Walfred wrote: >> Hi Simon, >> >> Thanks for your review! >> For all the comment above I agree, Thanks again! >> >> For the one below there are different point of views. >> How I see it: Very few sane people will add a symbols in a shared library that >> will collide like the case we presented here. If one does so how can the debugger >> help? > > I think one usual use case is plugins implemented with shared library. Although > the data symbols will commonly be static, and the plugin will only expose some > function symbols. > >> Providing the same value as the runtime or linker does? >> This one user already knows. >> Or providing what the debug information provides as value created by the library itself. >> In final end both are right. :| >> >> But when specifying the scope if user is provided the value of the debug info it should >> be easier to spot that there is something weird going on in the code. > > I think what you just said summarizes the problem well and I think it makes sense. > I just don't think I have enough experience about symbol handling to understand > the situation fully. Could another maintainer with more experience about symbols > give the final ok? I disagree. Having (gdb) frame #0 0x000000000040073b in function () at source.c:22 (gdb) print foo and: (gdb) print 'source.c':foo show different values when you're stopped in a function in the source.c file would look inconsistent to me. Actually, the patch introduces what looks like a related clear regression to me. With the print-file-var.exp test program, try stepping into get_version_2, and printing the this_version_id global. And then type finish. Vis: (gdb) s get_version_2 () at gdb.base/print-file-var-lib2.c:22 22 return this_version_id; (gdb) p this_version_id $1 = 203 (gdb) finish Run till exit from #0 get_version_2 () at gdb.base/print-file-var-lib2.c:22 0x000000000040073b in main () at gdb.base/print-file-var-main.c:24 24 int v2 = get_version_2 (); Value returned is $2 = 104 (gdb) GDB says "203", while the program returns "104". That looks like a bug to me. I'd expect the print to show me the current value of the variable in scope. In current master (without the patch), we get: (gdb) s get_version_2 () at gdb.base/print-file-var-lib2.c:22 22 return this_version_id; (gdb) p this_version_id $1 = 104 (gdb) finish Run till exit from #0 get_version_2 () at gdb.base/print-file-var-lib2.c:22 0x000000000040073b in main () at gdb.base/print-file-var-main.c:24 24 int v2 = get_version_2 (); Value returned is $2 = 104 Thanks, Pedro Alves