From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6866 invoked by alias); 21 Sep 2005 04:03:15 -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 6376 invoked by uid 22791); 21 Sep 2005 04:01:59 -0000 Received: from nevyn.them.org (HELO nevyn.them.org) (66.93.172.17) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Wed, 21 Sep 2005 04:01:59 +0000 Received: from drow by nevyn.them.org with local (Exim 4.52) id 1EHvnu-0001qH-BJ; Wed, 21 Sep 2005 00:01:54 -0400 Date: Wed, 21 Sep 2005 04:03:00 -0000 From: Daniel Jacobowitz To: Eli Zaretskii Cc: Ian Lance Taylor , michsnyd@cisco.com, gdb@sources.redhat.com, shebs@apple.com Subject: Re: Using reverse execution Message-ID: <20050921040154.GA7040@nevyn.them.org> Mail-Followup-To: Eli Zaretskii , Ian Lance Taylor , michsnyd@cisco.com, gdb@sources.redhat.com, shebs@apple.com References: <43309387.4020504@cisco.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.8i X-SW-Source: 2005-09/txt/msg00154.txt.bz2 On Wed, Sep 21, 2005 at 06:39:42AM +0300, Eli Zaretskii wrote: > > Cc: gdb@sources.redhat.com, shebs@apple.com > > From: Ian Lance Taylor > > Date: 20 Sep 2005 16:13:55 -0700 > > > > There is probably some cool use for which tracepoints are the > > obvious right answer, but I don't know what it is. > > In native debugging, tracepoints would be very useful to debug a > real-time program, or, more generally, a program where timing issues > are crucial to its correct operation. With such programs, normal GDB > usage disrupts the program operation and might even cause the program > to fail in ways that are unrelated to the bug you are looking for. Yes - and I've definitely tried to debug programs using GDB where this would have been helpful. E.G. when working on the MIPS port of NPTL. I ended up doing the manual equivalent using printf, but printf can actually be much higher overhead than in-memory tracepointing, and recompiling libc every time I needed to change the debugging output got to be a bit of a drag. -- Daniel Jacobowitz CodeSourcery, LLC