Re: Coexistence of libxml++ and libxml2 in the same process

[Murray Cumming <murrayc murrayc com>]

On Wed, 2010-11-03 at 18:43 +0100, Alessandro Pignotti wrote:
> I've a proposal, the code could be modified to call xmlRegisterNodeDefault 
> before any xmlNew* call and to reset the handler to the default one after 
> that.
> This approach would preserve the current interface while making libxml++ less 
> intrusive. I'm working on a patch to implement this solution, any comment?

I'd certainly like to preserve any existing state, and a patch for that
would be welcome.

Doing the initialization before the first use would be a) more difficult
to get right and b) possibly slowing down first use, when a slowdown is
most unwanted. So I'd like to consider that separately.

> 
> Regards,
> Alessandro
> 
> On Wednesday 03 November 2010 13:55:33 you wrote:
> > Hi everyone,
> > 
> > while trying to use the libxml++ in a browser plugin project (namely
> > lightspark) I've discovered that libxml++ seems not designed to coexist
> > with unwrapped usage of libxml2 in the same process. This is caused by the
> > static initialization and destruction done by Document::Init, I'm
> > reporting the snippet here for convenience
> > 
> > Document::Init::Init()
> > {
> >   xmlInitParser(); //Not always necessary, but necessary for thread safety.
> >   xmlRegisterNodeDefault(on_libxml_construct);
> >   xmlDeregisterNodeDefault(on_libxml_destruct);
> >   xmlThrDefRegisterNodeDefault(on_libxml_construct);
> >   xmlThrDefDeregisterNodeDefault(on_libxml_destruct);
> > }
> > 
> > Document::Init::~Init()
> > {
> >   xmlCleanupParser(); //As per xmlInitParser(), or memory leak will happen.
> > }
> > 
> > So the xml system is uninitialized when libxml++ is unloaded, even if there
> > are other users of libxml2 still living. Moreover, every xml node creation
> > go through libxml++ handlers, and this causes crashes here and there if
> > the calling code is expecting to use normal libxml2.
> > 
> > Any idea to make libxml++ more robust to such issues?
> > 
> > Regards,
> > Alessandro Pignotti
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