Hi,
I found a disturbing thing in QXmlPatterns - QPatternist::ItemMappingIterator::next() recursively calls itself, which leads to stack overflow if a XPath query is being done on a relatively large data set (in my example - about 15k xml elements). This results from a call in qnodesort.cpp:80:

Item::List nodes(m_operand->evaluateSequence(context)->toList());

The toList() method calls next() and all hell breaks loose.