From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-return-19344-listarch-gdb=sources.redhat.com@sources.redhat.com>
Received: (qmail 31310 invoked by alias); 7 Sep 2004 12:27:52 -0000
Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm
Precedence: bulk
List-Subscribe: <mailto:gdb-subscribe@sources.redhat.com>
List-Archive: <http://sources.redhat.com/ml/gdb/>
List-Post: <mailto:gdb@sources.redhat.com>
List-Help: <mailto:gdb-help@sources.redhat.com>, <http://sources.redhat.com/ml/#faqs>
Sender: gdb-owner@sources.redhat.com
Received: (qmail 31233 invoked from network); 7 Sep 2004 12:27:42 -0000
Received: from unknown (HELO cam-admin0.cambridge.arm.com) (193.131.176.58)
  by sourceware.org with SMTP; 7 Sep 2004 12:27:42 -0000
Received: from pc960.cambridge.arm.com (pc960.cambridge.arm.com [10.1.205.4])
	by cam-admin0.cambridge.arm.com (8.12.10/8.12.10) with ESMTP id i87CRQxm010406;
	Tue, 7 Sep 2004 13:27:26 +0100 (BST)
Received: from pc960.cambridge.arm.com (localhost.localdomain [127.0.0.1])
	by pc960.cambridge.arm.com (8.12.8/8.12.8) with ESMTP id i87CRfvv029038;
	Tue, 7 Sep 2004 13:27:41 +0100
Received: (from rearnsha@localhost)
	by pc960.cambridge.arm.com (8.12.8/8.12.8/Submit) id i87CRd3c029036;
	Tue, 7 Sep 2004 13:27:39 +0100
X-Authentication-Warning: pc960.cambridge.arm.com: rearnsha set sender to rearnsha@gcc.gnu.org using -f
Subject: Re: GDB 6.2 for ARM: bug in backtrace when in Thumb mode
From: Richard Earnshaw <rearnsha@gcc.gnu.org>
To: Thierry <goldy_gnu@yahoo.com>
Cc: gdb@sources.redhat.com
In-Reply-To: <20040907120204.43421.qmail@web61204.mail.yahoo.com>
References: <20040907120204.43421.qmail@web61204.mail.yahoo.com>
Content-Type: text/plain
Content-Transfer-Encoding: 7bit
Organization: GNU
Message-Id: <1094560059.8831.9.camel@pc960.cambridge.arm.com>
Mime-Version: 1.0
Date: Tue, 07 Sep 2004 12:27:00 -0000
X-SW-Source: 2004-09/txt/msg00050.txt.bz2

On Tue, 2004-09-07 at 13:02, Thierry wrote:
> Hi there,
>  
> I'm trying to debug an application compiled for the
> ARM in Thumb mode. The 'backtrace' command seems buggy
> as soon as there are more than 4 levels in the stack.
> Besides, with the same code compiled in ARM mode, it
> works perfectly.
>  
> Here's an example:
>  
> void dummy2(int a)
> {
>    int b;
>    b = a;
> }
>  
> void dummy1(void)
> {
>    dummy2(4);
> }
>  
> void dummy(void)
> {
>    dummy1();
> }
>  
> In my 'main', I call 'dummy()'.
> 
> When I go step-by-step until I step into 'dummy2', the
> 'bt' command gives the following result:
> #0  dummy2 (a=4) at MainModule/src/dummy.c:4
> #1  0xc000039c in dummy1 () at
> MainModule/src/dummy.c:9
> #2  0x00000000 in ?? ()
>  
> which is wrong!
>  
> The files have been compiled with arm-elf-gcc with the
> following options:
> -ggdb -gdwarf-2 -c -mapcs -fomit-frame-pointer -mthumb
> -mthumb-interwork -mlong-calls
> -fsigned-char -mstructure-size-boundary=8
> -fshort-enums
> 
> When I remove the option '-fomit-frame-pointer', it
> works.
>  
> Any idea?
>  

Most (all?) Released versions of gcc don't generate unwind information
for Thumb functions, so the unwinder gets confused if there's no frame
pointer.

It will be fixed in gcc-3.5, but I don't think it was fixed in time for
gcc-3.4.

R.