Re: [xml] Using variables with XPath expressions

[Daniel Veillard <veillard redhat 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)));
}
-------------------

Daniel

-- 
Daniel Veillard      | Red Hat Network http://redhat.com/products/network/
veillard redhat com  | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
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Sep 17-18 2001 Brussels Red Hat TechWorld http://www.redhat-techworld.com