Temporary inconsistent data inside Xerces2-J when removing a first child of a
node.
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Key: XERCESJ-1421
URL: https://issues.apache.org/jira/browse/XERCESJ-1421
Project: Xerces2-J
Issue Type: Improvement
Components: DOM (Level 3 Core)
Affects Versions: 2.9.1
Reporter: Ludger Bünger
Priority: Minor
Attachments: PreviousSiblingInconsistentDataPatch.txt
When removing a first child, currently there is a local field inside
ParentNode.internalRemoveChild that contains inconsistent data.
Since in this specific case the following code still performs correct, there is
currently no harm done.
However I think it should be fixed nonetheless since future changes to the code
might cause problems.
And here the description of the issue:
Xerces2-J uses an internal optimization by overloading the
ChildNode.previousSibling field.
1) If a node has a previous sibling, this field contains the previous sibling.
2) if a node is the first child of it's parent (and thus has no previous
sibling), this field is re-used for a different purpose and contains the last
sibling thus allowing quick access to the end of a node list
Now ChildNode.internalRemoveNode stores a reference to the previousSibling of
the removed node for normalization checking purposes in the local field
oldPreviousSibling.
However this is done after removal of the node is already done but before
null'ing of the tree structure fields of the node.
Since this node has already been removed, the isFirstChild() check fails and
instead of 'null' the last sibling is stored in the oldPreviousSibling field.
By chance the normalization checking code still works correct if the previous
sibling field contains the last sibling instead of the correct value 'null' but
this still should be fixed.
See attached patch.
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