[xml] Possible bug, libxml segfault

[Avleen Vig <avleen gmail com>]

Background:
We use libxml and libxslt in one of our applications (specifically, in
Python via lxml).

Recently we've seen our application dying at strange times for no
apparent reason.
We managed to get a core file out of one crash, and the results of
some of our debugging are here:
http://xml.pastebin.com/m70c259d6
(I'd be happy to poke more in a particular direction on there, I'm a
bit new to gdb :)

To me, it seems the parser is complaining while trying to parse the
namespaces in the <stylesheet> node in transforms/_base.xslt
The node for that opens like this:
<xsl:stylesheet  version="1.0"
                xmlns="http://www.w3.org/1999/xhtml";
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
                xmlns:tfxslt="http://tfnet.co.uk/ns/tfxslt";
                xmlns:fb="http://www.facebook.com/2008/fbml";
                extension-element-prefixes="tfxslt str exsl"
                exclude-result-prefixes="str exsl tfxslt fb"
                xmlns:error="http://www.woome.com/error/";>

I dug a little deeper and found a bunch of the "address out of bounds"
errors and thought I should ask here as I'm drawing a blank on where
to go next.

The problem happens intermittently, but usually several times a day. I
could probably reproduce it.
I also see the 'exclude-result-prefixes' mentioned in the backtrace,
could that be involved here?

Any suggestions you have would be much appreciated!