Debug error

[Marius Gedminas]

On Fri, Jan 20, 2012 at 11:17:30AM +0000, R Kimber wrote:
> On Fri, 20 Jan 2012 03:55:24 +0200
> Marius Gedminas wrote:
> 
> > On Thu, Jan 19, 2012 at 11:30:17PM +0000, R Kimber wrote:
> > > gdb is giving me the following:-
> > > 
> > > warning: the debug information found in
> > > "/usr/lib/debug//usr/lib/libxml2.so.2.7.8" does not match
> > > "/usr/lib/libxml2.so.2" (CRC mismatch).
> > > 
> > > warning: the debug information found in
> > > "/usr/lib/debug/usr/lib/libxml2.so.2.7.8" does not match
> > > "/usr/lib/libxml2.so.2" (CRC mismatch).

How can I try to reproduce this?  (Without building a 

> > What's the output of
> > 
> >   apt-cache policy libxml2
> 
> libxml2:
>   Installed: 2.7.8.dfsg-4
>   Candidate: 2.7.8.dfsg-4ubuntu0.1
>   Version table:
>      2.7.8.dfsg-4ubuntu0.1 0
>         500 http://archive.ubuntu.com/ubuntu/ oneiric-updates/main amd64 Packages
>         500 http://archive.ubuntu.com/ubuntu/ oneiric-security/main amd64 Packages
>  *** 2.7.8.dfsg-4 0
>         500 http://archive.ubuntu.com/ubuntu/ oneiric/main amd64 Packages
>         100 /var/lib/dpkg/status
>  
> > and
> > 
> >   apt-cache policy libxml2-dbg
> 
> libxml2-dbg:
>   Installed: 2.7.8.dfsg-4
>   Candidate: 2.7.8.dfsg-4ubuntu0.1
>   Version table:
>      2.7.8.dfsg-4ubuntu0.1 0
>         500 http://archive.ubuntu.com/ubuntu/ oneiric-updates/main amd64 Packages
>         500 http://archive.ubuntu.com/ubuntu/ oneiric-security/main amd64 Packages
>  *** 2.7.8.dfsg-4 0
>         500 http://archive.ubuntu.com/ubuntu/ oneiric/main amd64 Packages
>         100 /var/lib/dpkg/status

Ok, so the versions match.

(Although you should install the security update!)

I can reproduce your problem:

  $ gdb
  (gdb) file /usr/lib/libxml2.so
  Reading symbols from /usr/lib/libxml2.so...warning: the debug
  information found in "/usr/lib/debug//usr/lib/libxml2.so.2.7.8" does
  not match "/usr/lib/libxml2.so" (CRC mismatch).

  warning: the debug information found in
  "/usr/lib/debug/usr/lib/libxml2.so.2.7.8" does not match
  "/usr/lib/libxml2.so" (CRC mismatch).

  (no debugging symbols found)...done.

Looks like a bug to me.  This bug, actually:
https://bugs.launchpad.net/ubuntu/+source/libxml2/+bug/669852

> > and
> > 
> >   apt-cache policy libxml2-dbgsym
> 
> N: Unable to locate package libxml2-dbgsym
> 
> Maybe this is the problem, but Synaptic does not show a libxml2-dbgsym
> package as being available.

That's fine; it comes from the ddebs repository which is not enabled by
default.  See https://wiki.ubuntu.com/DebuggingProgramCrash for more
information.

Most packages do not have a -dbg version, but almost all of them have
-dbgsym.  Libxml2 has both, for some reason.  I just wanted to make sure
which one you were using.

Incidentally, when I install libxml2-dbgsym, gdb is then able to find
libxml2's debug symbols.  I suggest you do the same.

Regards,
Marius Gedminas
-- 
C gives you enough rope to hang yourself. C++ also gives you the tree object to
tie it to.
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