Re: [xml] MacOSX specific problem when using xmlXPathNodeSetIsEmpty()

[Steve Ball <Steve Ball zveno com>]

xmlXPathNodeSetIsEmpty is a macro defined in include/libxml/xpath.h:

#define xmlXPathNodeSetIsEmpty(ns)                                      
\
    (((ns) == NULL) || ((ns)->nodeNr == 0) || ((ns)->nodeTab == NULL))

so all it is doing is comparing a few data values to zero.  I cannot 
see what the problem might be;
there are no compiler errors when I build the code.

I notice you're using C++.  How is _query defined?

Cheers,
Steve Ball

On 18/06/2004, at 7:14 AM, Håkon Skjelten wrote:

> Hi
>
> I'm working on a project where we use libxml2 to store level data. The 
> code
> works perfectly on GNU/Linux (PPC/i386/AMD64) but it fails on MacOSX.
>
> The code that fails is the xmlXPathNodeSetIsEmpty(_query->nodesetval)
> function call. For some reason it returns TRUE on MacOSX even though 
> this is
> not correct (same code & XML file returns FALSE in GNU/Linux). All 
> other
> libxml2 functions seems to work fine on the Mac.
>
> The method that fails:
> int XMLParser::query_start(std::string xpath)
> {
>   if (_query != NULL)
>      return -1;
>
>   _query_element = 0;
>   xmlXPathContextPtr context = xmlXPathNewContext(_xmlDocument);
>   _query = xmlXPathEvalExpression( (xmlChar*)xpath.c_str(), context);
>   xmlXPathFreeContext(context);
>
> /*
>   This does not work either:
>      if (xmlXPathNodeSetGetLength(_query->nodesetval) == 0) {
> */
>   if (xmlXPathNodeSetIsEmpty(_query->nodesetval)) {
>      _query_matches = 0;
>      _query_attr = NULL;
>   } else {
>      _query_matches = _query->nodesetval->nodeNr;
>      _query_attr =  _query->nodesetval->nodeTab[0]->properties;
>   }
>
>   return 0;
> }
>
> _query_matches always equals 0 on MacOSX (and if I skip the entire 
> test and
> set _query_matches = _query->nodesetval->nodeNr; I get a segmentation 
> fault).
>
> The same problem occur both on old and new versions of libxml2.
>
> Is this a known problem? Are there any known workarounds? Suggestions?
>
>
> Regards,
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Håkon Skjelten  (skjelten pvv org)
> Student, Engineering Cybernetics
> Norwegian University of Science and Technology
> _______________________________________________
> xml mailing list, project page  http://xmlsoft.org/
> xml gnome org
> http://mail.gnome.org/mailman/listinfo/xml

---

Steve Ball            |   XSLT Standard Library   | Training & Seminars
Zveno Pty Ltd         |     Web Tcl Complete      |   XML XSL Schemas
http://www.zveno.com/ |      TclXML TclDOM        | Tcl, Web Development
Steve Ball zveno com  +---------------------------+---------------------
Ph. +61 2 6242 4099   |   Mobile (0413) 594 462   | Fax +61 2 6242 4099