Re: [xml] XPathObject and user/user2

[Christian Stocker <chregu bitflux ch>]

On Fri, 2002-11-29 at 13:17, Daniel Veillard wrote:
> On Fri, Nov 29, 2002 at 12:50:17PM +0100, Christian Stocker wrote:
> > Hi
> >
> > I'm trying to debug (once again) PHPs domxml extension.
> >
> > The XPath part of domxml uses obj->user (obj is a xmlXPathObjectPtr) for
>
>   that's bad !
>
> > storing a PHP/Zend internal pointer. But when I look into the source of
> > xpath.c, then I see that obj->user is also used internally there. 
>
>   yes, user is needed for XSLT extensions and XPointer entensions. 
> user2 is used solely for XPointer, so this might be safer to use.
>
> > Is my assumption right, that obj->user (and user2 for that matter),
> > shouldn't be used for application side storage of pointers like _private
> > in other structs? 
>
>   right
>
> > Is there an alternative for that (interpreting
> > http://mail.gnome.org/archives/xml/2002-June/msg00131.html there
> > isn't..) ?
>
>    there isn't in general, user2 seems safer.
>
> > If so, I wonder why it never crashed on me, but it could explain some
> > memory leaks on my side.
>
>    Seems unlikely unless it also uses XSLT with the same objects,
> but having a crash sounds more probable, code like:
>    xmlFreeNodeList((xmlNodePtr) obj->user);
> with a pointer to PHP objects is likely to make a lot of damages !
> And this is part of xmlXPathFreeObject(), so this hack looks really really
> dangerous.

I feared that... It looks like I have to rewrite this XPath stuff then,
since there are unfortunately no _private members in those structs.

Anyway, thanks a lot for your answer.

christian