From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26997 invoked by alias); 15 Sep 2005 15:14:33 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 26981 invoked by uid 22791); 15 Sep 2005 15:14:26 -0000 Received: from nitzan.inter.net.il (HELO nitzan.inter.net.il) (192.114.186.20) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Thu, 15 Sep 2005 15:14:26 +0000 Received: from HOME-C4E4A596F7 (IGLD-83-130-204-57.inter.net.il [83.130.204.57]) by nitzan.inter.net.il (MOS 3.6.5-GR) with ESMTP id BKZ05445 (AUTH halo1); Thu, 15 Sep 2005 18:14:22 +0300 (IDT) Date: Thu, 15 Sep 2005 15:14:00 -0000 Message-Id: From: Eli Zaretskii To: Stan Shebs CC: gdb@sources.redhat.com In-reply-to: <43290862.9040204@apple.com> (message from Stan Shebs on Wed, 14 Sep 2005 22:36:34 -0700) Subject: Re: Using reverse execution Reply-to: Eli Zaretskii References: <432628AA.2040808@apple.com> <43277083.1040708@apple.com> <4328A574.5080906@apple.com> <43290862.9040204@apple.com> X-SW-Source: 2005-09/txt/msg00108.txt.bz2 > Date: Wed, 14 Sep 2005 22:36:34 -0700 > From: Stan Shebs > Cc: gdb@sources.redhat.com > > Cool! Care to share any details?? I thought I was doing just that... If you mean to try to answer the questions you rose, like whether to try to undo system calls, then I'm afraid I don't remember what happened on the system where I used such a debugger (it was quite some time ago). Anyway, one of the latest issues of DrDobb's ran an article about debuggers that support similar features, with pointers to existing products, so you could try to find them to get some ideas about usability of this feature. > >IMHO, tracepoints remain a curiosity because they were never > >implemented on a large enough number of platforms. Lack of native > >support, in particular, is the main reason for its non-use. > > > But don't you think it's telling that not one single person was > willing to go to the trouble of implementing it on more platforms? I can only speak for myself. You once wrote here that tracepoints in native debugging is something to kill for, but I myself didn't have time and resources to make that happen. Basically, the lesson from tracepoints is, I think, that features that GDB developers (as opposed to users) don't need too much will not materialize. > >We could discuss these questions one by one. But we shouldn't fear > >them to the degree that prevents us from starting to implement this > >feature. > > > Depending on the answers, the project could be fatally flawed. I don't think so. > For instance, if the ability to undo system calls is critical for > usability, that pretty much relegates reversal to simulator targets > only - not interesting for my user base. That's why I wanted to talk > about usage patterns; if users don't need the debugger to do the > incredibly hard things, then we can get to something useful sooner. I suspect that answers to most or all of your questions are "sometimes". I.e., sometimes the user will want to undo the system call, and sometimes not. I even think that sometimes they will want to _redo_ the system call, since the bug might only happen when the syscall is made. This might mean we will have to put in code to ask the user what to do with a syscall.