From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20679 invoked by alias); 5 Jun 2003 15:59:12 -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 20172 invoked from network); 5 Jun 2003 15:58:56 -0000 Received: from unknown (HELO crack.them.org) (146.82.138.56) by sources.redhat.com with SMTP; 5 Jun 2003 15:58:56 -0000 Received: from dsl093-172-017.pit1.dsl.speakeasy.net ([66.93.172.17] helo=nevyn.them.org ident=mail) by crack.them.org with asmtp (Exim 3.12 #1 (Debian)) id 19Nx9M-000571-00; Thu, 05 Jun 2003 10:59:36 -0500 Received: from drow by nevyn.them.org with local (Exim 3.36 #1 (Debian)) id 19Nx8d-0007JX-00; Thu, 05 Jun 2003 11:58:51 -0400 Date: Thu, 05 Jun 2003 15:59:00 -0000 From: Daniel Jacobowitz To: Andrew Cagney Cc: gdb@sources.redhat.com Subject: Re: Use of lval_register? Message-ID: <20030605155851.GA28099@nevyn.them.org> Mail-Followup-To: Andrew Cagney , gdb@sources.redhat.com References: <3EDF5520.8030009@redhat.com> <20030605151750.GA25587@nevyn.them.org> <3EDF66A8.4030003@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3EDF66A8.4030003@redhat.com> User-Agent: Mutt/1.5.1i X-SW-Source: 2003-06/txt/msg00069.txt.bz2 On Thu, Jun 05, 2003 at 11:50:00AM -0400, Andrew Cagney wrote: > > >lval_reg_frame_relative is a relatively recent addition, I believe, > >added to fix some particular problem with values stored in two places. > >Probably around the HP merge? But that's just a guess. > > Ah. > > >I think that lval_reg_frame_relative, lval_memory, and lval_register > >should all be combined to an lval_location which takes the frame and a > >description of a location, personally. > > These will all need to live in harmony for a wile though. > > >>In fact, I'm even wondering if GDB should always be setting it to > >>lval_reg_frame_relative, consider the following: > >> > >>(gdb) b main > >>Breakpoint 1 at 0x1802f84: file gdb.c, line 30. > >>(gdb) run > >>Starting program: gdb > >>Breakpoint 1, main (argc=1, argv=0x7fffe434) at > >>/home/scratch/GDB/src/gdb/gdb.c:30 > >>30 memset (&args, 0, sizeof args); > >>(gdb) n > >>31 args.argc = argc; > >>(gdb) > >>32 args.argv = argv; > >>(gdb) print args > >>$1 = {argc = 1, argv = 0x0, use_windows = 0, interpreter_p = 0x0} > >> > >>At this point $1 contains not just args value but also it's location. > >>Modify the target state ... > >> > >>(gdb) n > >>33 args.use_windows = 0; > >>(gdb) print args > >>$2 = {argc = 1, argv = 0x7fffe434, use_windows = 0, interpreter_p = 0x0} > >>(gdb) print $1 > >>$3 = {argc = 1, argv = 0x0, use_windows = 0, interpreter_p = 0x0} > > > > > >Agh! That's not right at all! Although I'm not entirely clear on why > >it moved? > > The ``print $1''? That output is correct. GDB saves the value so that > it can be refered back to later without having it change. Oh right. So the value is coming from the cache. > >I guess the question is, what _should_ happen if a variable moves? > >e.g. we switch to a different item on its location list. > > From the users view point, the variable hasn't moved. Hence the > assignment: > > $1.argc = N > > should always work. Should that assignment update the cached $1 value > as well, hmm.... I think it should update the cached copy. I'm not so sure it should update the in-memory copy, if the var has moved. That would require re-evaluating the expression that produced $1 wouldn't it? -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer