From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 27112 invoked by alias); 5 Jun 2003 16:23:43 -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 27100 invoked from network); 5 Jun 2003 16:23:42 -0000 Received: from unknown (HELO crack.them.org) (146.82.138.56) by sources.redhat.com with SMTP; 5 Jun 2003 16:23:42 -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 19NxXK-0005A7-00; Thu, 05 Jun 2003 11:24:22 -0500 Received: from drow by nevyn.them.org with local (Exim 3.36 #1 (Debian)) id 19NxWc-0008O3-00; Thu, 05 Jun 2003 12:23:38 -0400 Date: Thu, 05 Jun 2003 16:23:00 -0000 From: Daniel Jacobowitz To: Andrew Cagney Cc: gdb@sources.redhat.com Subject: Re: Use of lval_register? Message-ID: <20030605162338.GB30522@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> <20030605155851.GA28099@nevyn.them.org> <3EDF6C02.90807@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3EDF6C02.90807@redhat.com> User-Agent: Mutt/1.5.1i X-SW-Source: 2003-06/txt/msg00072.txt.bz2 On Thu, Jun 05, 2003 at 12:12:50PM -0400, Andrew Cagney wrote: > >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. > > Actually, these are separate but related problems: > > - a location expression determines that a value is in REGNUM N in FRAME F. > > - the CFI then determines that REGNUM N in frame F is actually in REGNUM > M in frame G. > > Printing a variable relies on both mechanisms, printing $r1 uses just > the first. > > >>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. > > It's comming from GDB's infinite value history pool (the word cache > suggests that it is eventually flushed, which it isn't :-). > > > > > > >>>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? > > Eventually. For the moment I'm just worred about getting it to > re-evaluate the registers the value is assumed to reside in. > > Or should it only modify the history pool (modifying memory is weird > here, but where to draw the line is also weird). After some more thought, I suppose it should modify both the pool and memory. It's just not clear how to find out where in memory it should be, now... -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer