[xml] MacOSX specific problem when using xmlXPathNodeSetIsEmpty()

[Håkon Skjelten <skjelten pvv org>]

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