RE: [xml] Using variables with XPath expressions

["Vakoc, Mark" <Mark_Vakoc jdedwards com>]

> > On Tue, Jul 03, 2001 at 04:00:02PM -0600, Vakoc, Mark wrote:
> > My fix (I believe) was to correct xmlXPathCompOpEval to use a copy of the
> > variable value rather than the value directly.  I have done a fair amount
of
> > testing using this and all my expressions using variables return the
> > expected results.  
> >
> >      case XPATH_OP_VARIABLE: {
> >          if (op->ch1 != -1)
> >              xmlXPathCompOpEval(ctxt, &comp->steps[op->ch1]);
> >          if (op->value5 == NULL)
> > --           valuePush(ctxt,
> > --               xmlXPathVariableLookup(ctxt->context, op->value4));
> > ++           valuePush(ctxt,xmlXPathObjectCopy(
> > xmlXPathVariableLookup(ctxt->context, op->value4)) );
> >
> >
> > Daniel - Can you confirm that this is the right approach.
>
> That would be one way to do it, but would change the interface between
> libxml and libxslt (which uses the xmlXPathRegisterVariableLookup() 
> mechanism and where the registered lookup function does the copy), 
> so I would rather fix the default Variable lookup to do this copy
> and hence change the end of xmlXPathVariableLookupNS() to
>
> -------------------
>    if (ctxt->varHash == NULL)
>        return(NULL);
>    if (name == NULL)
>        return(NULL);
>
>    return(xmlXPathObjectCopy((xmlXPathObjectPtr)
>                xmlHashLookup2(ctxt->varHash, name, ns_uri)));
> }
> -------------------

This works for me.  I tested it in my app (nasty xpath expressions utilizing
6-8 variables) and it worked without issue.  

mark.