On Thu, Apr 10, 2014 at 01:27:30PM +0200, Martin Ba wrote:
> Hi all!
>
> It would appear that when you have a scenario like this
>
> + + + +
> // Thread 1:
> xmlInitParser();
> // ...
> // anything that sets the last error, e.g.:
> xmlReadFile("file isn't there", NULL, XML_PARSE_NOBLANKS);
>
> // Thread 2:
> xmlCleanupParser();
> + + + +
>
> even if (in Thread_2) you correctly call xmlCleanupParser() (once) at the
> very end and don't do anything with libxml2 afterwards, the global error
> will be leaked.
>
> (I also tried with the latest Windows binaries I could find -- 2.9.1 -- same
> problem.)
>
> Is this a known problem? Any fix for this?
>
> Note the workaround for me is to call xmlResetLastError() after processing
> any error received from libxml, in which case the global last error is
> immediately cleaned up.
>
>
> cheers,
> Martin
>
> p.s.: Why would anyone do this?:
> * Once scenario is when DLL's are loaded/unloaded dynamically.
> * Where I actually hit this is we have a .NET/C# application that loads a
> C++ module that contains a global initialization object for libxml2 that
> does init and cleanup. In a managed application, destructors of global
> objects are not necessarily executed on the same thread as their
> constructors.
Yes that's a known limitation, and why I suggest to run
xmlInitParser() in the main thread. Also note of the danger of running
xmlCleanupParser() on unloading, as some of the libraries you linked to
(possibly indirectly) could also run libxml2. So something to do only
in a very controlled context, i have had the case of extension mechanism
are being used, and then those use libxml2 in turn and havoc follows.
If I were redoing libxml2 now (or had been in last 10 years) there
would be no global state, but with the API as-is and the need to keep
ABI we are stuck with it :-\ mistake done back in 98 ....
Daniel
--
Daniel Veillard | Open Source and Standards, Red Hat
veill...@redhat.com | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | virtualization library http://libvirt.org/
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