[xml] libxml2 API crazy?

[Nikita Churaev <lamefun x0r gmail com>]

#include <libxml/parser.h>
#include <libxml/tree.h>
#include <stdio.h>

int
main (int argc, char** argv)
{
  xmlDocPtr doc = xmlReadMemory("<doc/>", 6, "egg.xml", NULL, 0);

                  /* XmlNode */            /* XmlDoc */
  printf("%s\n", (doc->children->parent == doc) ? "true" : "false");
  return 0;
}

This gives out "true"... Why? xmlNode.parent is xmlNodePtr... So I can't
just rely on xmlNode pointers to actually point to xmlNode? I looked all
around the API reference and tutorials and found nothing on this topic.