From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19269 invoked by alias); 15 Aug 2002 13:53:15 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 19154 invoked from network); 15 Aug 2002 13:53:12 -0000 Received: from unknown (HELO crack.them.org) (65.125.64.184) by sources.redhat.com with SMTP; 15 Aug 2002 13:53:12 -0000 Received: from nevyn.them.org ([66.93.61.169] ident=mail) by crack.them.org with asmtp (Exim 3.12 #1 (Debian)) id 17fL3q-00035B-00; Thu, 15 Aug 2002 08:53:14 -0500 Received: from drow by nevyn.them.org with local (Exim 3.35 #1 (Debian)) id 17fL4E-0005zX-00; Thu, 15 Aug 2002 09:53:38 -0400 Date: Thu, 15 Aug 2002 06:53:00 -0000 From: Daniel Jacobowitz To: Andrew Cagney Cc: gdb-patches@sources.redhat.com Subject: Re: [RFC] breakpoints and function prologues... Message-ID: <20020815135338.GA22990@nevyn.them.org> Mail-Followup-To: Andrew Cagney , gdb-patches@sources.redhat.com References: <6AF1E816-A97C-11D6-B045-00039379E320@> <3D5B42B9.6070201@ges.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3D5B42B9.6070201@ges.redhat.com> User-Agent: Mutt/1.5.1i X-SW-Source: 2002-08/txt/msg00362.txt.bz2 On Thu, Aug 15, 2002 at 01:57:13AM -0400, Andrew Cagney wrote: > >I agree with Jim here. I think most folks are actually surprised to find > >that if they break on the "{" beginning a function (or indeed anywhere > >before the first executable line of code) then their backtrace will not be > >correct. Understanding why this is so requires you to "pay attention to > >the man behind the curtain", and that we breaks the illusion that source > >code maps straight-forwardly onto the running program. Where this extra > >knowledge is helpful (like when debugging optimized code) it is fine to > >require folks to have it. But here, where it really doesn't do any good, > >I think it is just confusing. And, of course, it causes big heartburn for > >GUIs the varobj code, as I said earlier. > > > >I doubt that "{" breaks on the prologue is a crucial feature of gdb, and > >given that there are other ways to do this, I don't think it is really > >worth supporting... > > Michael is right here. If a CLI user sets a breakpoint on a line (with > code) then that user clearly wants the breakpoint set on that line. Sure, if the user knows there's code there. I don't think most of our users would understand that there is code on the "{", or what it is for - and I don't think that breaking by line number should break on code inserted by the compiler rather than the user. So I have to agree with Jim (both Jims, I think?). > If an architecture can't unwind the frame for that breakpoint address > then that is a bug in the architecture and/or GDB. The main reason the > average prologue analyzer doesn't handle breakpoints in the prologue is, > I think, more a factor of not being tested then of being ``hard''. Most of our ports don't support it, however. -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer