Please describe the problem:
When adding a child list to a node using xmlAddchildList,  each child has its doc pointer updated to match the parent.  The xmlSetTreeDoc call is used on all the children except the last one. As a result,  the last child's children do not get updated with the correct doc pointer.

The offending code is in tree.c  line 3215..

Steps to reproduce:
This contrived example demonstrates one way to trigger the problem.

xmlDocPtr doc = xmlNewDoc( NULL );
xmlNodePtr docnode = xmlNewChild( doc, NULL, "docnode", NULL );
xmlNodePtr n1 = xmlNewNode( NULL, "node1" );
xmlAddChild(  n1, xmlNewNode( NULL, "node2" );
xmlAddChildList( docnode, n1 );
printf( n1->children->doc->version ); 


Actual results:
the printf line will cause an access violation as the doc pointer is null.

Expected results:
no crash to occur..  i.e.  n1's children have been updated correctly.

Does this happen every time?
yes

Other information: