xml4r/libxml-ruby — pull request #76 by lucijan (2013-08-27 15:19:39+00:00)
Title: Don't mark nodes that aren't handled by ruby

Don't register with a GC mark callback for node types that don't
have node->_private. This fixes a crash that occures if rxml_node_mark is
called with a pointer to a node that has already been freed by libxml.

Unfortunately i can't provide any compact test case / way to reproduce this bug
and prove the fix. However it works for our needs.