From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31341 invoked by alias); 1 Oct 2003 14:49:44 -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 31326 invoked from network); 1 Oct 2003 14:49:43 -0000 Received: from unknown (HELO nevyn.them.org) (66.93.172.17) by sources.redhat.com with SMTP; 1 Oct 2003 14:49:43 -0000 Received: from drow by nevyn.them.org with local (Exim 4.22 #1 (Debian)) id 1A4iIL-0001Fp-Sv; Wed, 01 Oct 2003 10:49:37 -0400 Date: Wed, 01 Oct 2003 14:49:00 -0000 From: Daniel Jacobowitz To: Josef Zlomek Cc: gdb@sources.redhat.com Subject: Re: Problem with location lists and variables on stack Message-ID: <20031001144937.GA4613@nevyn.them.org> Mail-Followup-To: Josef Zlomek , gdb@sources.redhat.com References: <20031001144330.GA11707@artax.karlin.mff.cuni.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031001144330.GA11707@artax.karlin.mff.cuni.cz> User-Agent: Mutt/1.5.1i X-SW-Source: 2003-10/txt/msg00026.txt.bz2 On Wed, Oct 01, 2003 at 04:43:30PM +0200, Josef Zlomek wrote: > Hello, > > I writing a better pass (variable tracking) for GCC which finally emits > location lists for variables. (If you are insterested it is at > http://artax.karlin.mff.cuni.cz/~zlomj9am/download/vt-main.patch > It still contains many debugging checks and (disabled) prints.) > > Let the local variables and (some) arguments be addressed using stack pointer, > for example x86-64 architecture with variables addressed using %rsp. > The address emitted for variables located on stack by my new patch is always > DW_OP_fbreg + constant. > > When I was testing the emitted debug info with mainline GDB I found that > GDB probably does not adjust addresses of variables when stack pointer changes > (like because of "pushq" instruction) if using location lists. > I think GDB should adjust the address of %rsp addressed variables according to > change of %rsp (probably DWARF2 sais so for DW_OP_fbreg). I think it is a > better solution than emitting new locations to location list for all variables > located on stack after each "push" and "pop" which would cause too large debug > info. > > When I looked to gdb/dwarf2loc.c I see there: > /* FIXME: cagney/2003-03-26: This code should be using > get_frame_base_address(), and then implement a dwarf2 specific > this_base method. */ > Probably this is related to my problem. The FIXME is a cleanliness problem. We do evaluate DW_AT_frame_base, so it _ought_ to work. > I tested it on attached C file, assembler with debug info and x86-64 binary > is attached too. Do you suppose you could produce an x86 (ia32) testcase? I don't have x86-64 hardware available yet. The debug info looks right so I'd like to get my fingers into the problem. -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer