gdb 6.6: incomplete backtraces ?

gdb 6.6: incomplete backtraces ?

[Markus.Grunwald]

Hello,

while researching for another problem, I found this :

gdb 6.6, compiled by myself:
--------------------------------------------------------------------------------
gru@CMDevLin2 >/home/gru/gdb-6.6/bin/gdb dafit_x86.bin 
GNU gdb 6.6
(gdb) catch fork
Catchpoint 1 (fork)
(gdb) run
[...]
Catchpoint 1 (forked process 26023), 0xb7fa1410 in ?? ()
(gdb) bt
#0  0xb7fa1410 in ?? ()
#1  0x00000001 in ?? ()
#2  0x00000000 in ?? ()
(gdb) show backtrace limit
An upper bound on the number of backtrace levels is unlimited.
--------------------------------------------------------------------------------

Hey, that's quite short ! No matter which catchpoint is hit, I get only 3 
frames ...


gdb 6.3, debian:
--------------------------------------------------------------------------------
gru@CMDevLin2 >/usr/bin/gdb dafit_x86.bin 
GNU gdb 6.3-debian

(gdb) catch fork
Catchpoint 1 (fork)
(gdb) run
[...]
Catchpoint 1 (forked process 25938), 0xb7f66410 in ?? ()
(gdb) bt
#0  0xb7f66410 in ?? ()
#1  0x00000001 in ?? ()
#2  0x00000000 in ?? ()
#3  0xb727661e in strtold_l () from /lib/tls/i686/cmov/libc.so.6
#4  0xb73ebadd in system () from /lib/tls/i686/cmov/libpthread.so.0
#5  0x080f9827 in CPTApplication::SetupTmpDir (this=0x90f7260)
    at 
/home/gru/projects/vxp/branches/branch-0-2-00-X/Dafit_Code/dafit2/dafit2/CPTApplication.cpp:1676
#6  0x080f50a4 in CPTApplication::CPTApplication (this=0x90f7260, 
nSuccess=@0xbfdbe0b4, nArgc=1, aszArgv=0xbfdbe134)
    at 
/home/gru/projects/vxp/branches/branch-0-2-00-X/Dafit_Code/dafit2/dafit2/CPTApplication.cpp:467
#7  0x080fbafa in main (nArgs=1, aszArgs=0xbfdbe134) at 
/home/gru/projects/vxp/branches/branch-0-2-00-X/Dafit_Code/dafit2/dafit2/main.cpp:55
--------------------------------------------------------------------------------

That's better ! What could this be ?

Mit freundlichen Grüßen

Markus Grunwald
Softwareentwicklung

PRÜFTECHNIK Condition Monitoring GmbH
Oskar-Messter-Straße 19-21
85737 Ismaning
www.pruftechnik.com
Tel: +49 (0)89 99616177
Fax: +49 (0)89 99616200

PRÜFTECHNIK Condition Monitoring GmbH
Sitz Ismaning / HRB 145655 München 
Geschäftsführer: Johann Lösl, Roland Schühle

Ein Unternehmen der PRÜFTECHNIK-Gruppe

Re: gdb 6.6: incomplete backtraces ?

[Daniel Jacobowitz]

On Thu, Mar 08, 2007 at 04:04:27PM +0100, Markus.Grunwald@pruftechnik.com wrote:
> Hello,
> 
> while researching for another problem, I found this :
> 
> gdb 6.6, compiled by myself:
> --------------------------------------------------------------------------------
> gru@CMDevLin2 >/home/gru/gdb-6.6/bin/gdb dafit_x86.bin 
> GNU gdb 6.6
> (gdb) catch fork
> Catchpoint 1 (fork)
> (gdb) run
> [...]
> Catchpoint 1 (forked process 26023), 0xb7fa1410 in ?? ()
> (gdb) bt
> #0  0xb7fa1410 in ?? ()
> #1  0x00000001 in ?? ()
> #2  0x00000000 in ?? ()
> (gdb) show backtrace limit
> An upper bound on the number of backtrace levels is unlimited.
> --------------------------------------------------------------------------------
> 
> Hey, that's quite short ! No matter which catchpoint is hit, I get only 3 
> frames ...

What does info shared say is at that address?  Anything?

It usually helps to install the Debian libc6-dbg package and configure
your GDB with --prefix=/usr.  That will improve backtraces through the
system libraries.

-- 
Daniel Jacobowitz
CodeSourcery

Re: gdb 6.6: incomplete backtraces ?

[Markus.Grunwald]

Hello,

> 
--------------------------------------------------------------------------------
> > gru@CMDevLin2 >/home/gru/gdb-6.6/bin/gdb dafit_x86.bin 
> > GNU gdb 6.6
> > (gdb) catch fork
> > Catchpoint 1 (fork)
> > (gdb) run
> > [...]
> > Catchpoint 1 (forked process 26023), 0xb7fa1410 in ?? ()
> > (gdb) bt
> > #0  0xb7fa1410 in ?? ()
> > #1  0x00000001 in ?? ()
> > #2  0x00000000 in ?? ()
> > (gdb) show backtrace limit
> > An upper bound on the number of backtrace levels is unlimited.
> > 
> 
--------------------------------------------------------------------------------
> > 
> > Hey, that's quite short ! No matter which catchpoint is hit, I get 
only 3 
> > frames ...
> 
> What does info shared say is at that address?  Anything?

Catchpoint 1 (forked process 27093), 0xb7f10410 in ?? ()
(gdb) bt
#0  0xb7f10410 in ?? ()
#1  0x00000001 in ?? ()
#2  0x00000000 in ?? ()
(gdb) info shared
From        To          Syms Read   Shared Object Library
0xb7f11790  0xb7f222cf  Yes         /lib/ld-linux.so.2
0xb7eeb0e0  0xb7ef7a74  Yes         /lib/libbz2.so.1.0
0xb7700f40  0xb7bf0880  Yes         /opt/qt/x86/qt3/lib/libqt-mt.so.3
[...]

Hmm, seems we didn't hit anything... 
This is for gdb 6.3:

Catchpoint 1 (forked process 27776), 0xb7f77410 in ?? ()
(gdb) bt
#0  0xb7f77410 in ?? ()
#1  0x00000001 in ?? ()
#2  0x00000000 in ?? ()
#3  0xb728761e in strtold_l () from /lib/tls/i686/cmov/libc.so.6
[...]
(gdb) info shared
From        To          Syms Read   Shared Object Library
0xb7f520e0  0xb7f5ea74  Yes         /lib/libbz2.so.1.0
0xb7767f40  0xb7c57880  Yes         /opt/qt/x86/qt3/lib/libqt-mt.so.3
0xb74f1660  0xb74fb174  Yes         /usr/lib/libXext.so.6
0xb7417c40  0xb74a54f4  Yes         /usr/lib/libX11.so.6
[...]


> It usually helps to install the Debian libc6-dbg package and configure
> your GDB with --prefix=/usr.  That will improve backtraces through the
> system libraries.

Sounds interresing... But I am currently testing a lot of gdb stuff here 
and don't want to interfere with my colleagues who work on the same 
machine, so I don't want to use --prefix=/usr ...

cu
Markus Grunwald

Re: gdb 6.6: incomplete backtraces ?

[Daniel Jacobowitz]

On Thu, Mar 08, 2007 at 04:47:37PM +0100, Markus.Grunwald@pruftechnik.com wrote:
> Catchpoint 1 (forked process 27093), 0xb7f10410 in ?? ()
> (gdb) bt
> #0  0xb7f10410 in ?? ()
> #1  0x00000001 in ?? ()
> #2  0x00000000 in ?? ()
> (gdb) info shared
> From        To          Syms Read   Shared Object Library
> 0xb7f11790  0xb7f222cf  Yes         /lib/ld-linux.so.2
> 0xb7eeb0e0  0xb7ef7a74  Yes         /lib/libbz2.so.1.0
> 0xb7700f40  0xb7bf0880  Yes         /opt/qt/x86/qt3/lib/libqt-mt.so.3
> [...]
> 
> Hmm, seems we didn't hit anything... 

Check /proc/27093/maps.  Most likely it's the .plt section of
ld-linux.so.2.
> Sounds interresing... But I am currently testing a lot of gdb stuff here 
> and don't want to interfere with my colleagues who work on the same 
> machine, so I don't want to use --prefix=/usr ...

You don't need to install it there, just configure it there.  Or set
debug-file-directory by hand - see the manual for more on that.

-- 
Daniel Jacobowitz
CodeSourcery