Attached modified patch to handle xmlCopyNode returning NULL. The patch is larger because xmlerrcxt must be passed to xml_xmlnodetoxmltype (xmlerrcxt is needed for calling xml_ereport).
From libxml2 source, it turns out that the other cases that xmlCopyNode will return NULL will not happen. So in this patch i assume that the only case is memory exhaustion.
But i found some bug in libxml2's code, because we call xmlCopyNode with 1 as the second parameter, internally xmlCopyNode will call xmlStaticCopyNode recursively via xmlStaticCopyNodeList. And xmlStaticCopyNodeList doesn't check the return of xmlStaticCopyNode whether it's NULL. So if someday the recursion returns NULL (maybe because of memory exhaustion), it will SEGFAULT.
Knowing this but in libxml2 code, is this patch is still acceptable?
