Markus Sunela created NETBEANS-2982:
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Summary: UndoRedo class causes ArrayIndexOutOfBoundsException
Key: NETBEANS-2982
URL: https://issues.apache.org/jira/browse/NETBEANS-2982
Project: NetBeans
Issue Type: Bug
Components: platform - Window System
Affects Versions: 11.1, 11.0, 10.0
Reporter: Markus Sunela
After a lot of UndoableEdits have been added to an UndoManager in a platform
application, the UI sometimes starts to show the exception as it tries to
update the name of the next undoable edit for the menus:
{code:java}
java.lang.ArrayIndexOutOfBoundsException: 100 >= 100
at java.base/java.util.Vector.elementAt(Vector.java:496)
at org.openide.awt.UndoRedo$Manager.editToBeUndone(UndoRedo.java:403)
at org.openide.awt.UndoRedo$Manager.canUndo(UndoRedo.java:224)
at
org.openide.awt.UndoRedo$Manager.getUndoPresentationName(UndoRedo.java:501)
at org.openide.actions.UndoRedoAction.getName(UndoRedoAction.java:171)
at org.openide.actions.UndoRedoAction.run(UndoRedoAction.java:139)
at
java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at
java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
at
org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:136)
{code}
This seems to be due to incorrect handling of indexOfNextAdd in the
UndoRedo.java
([https://github.com/apache/netbeans/blob/master/platform/openide.awt/src/org/openide/awt/UndoRedo.java)].
The indexOfNextAdd can be larger (more than by one) than the length of the
edits Vector, and especially in editToBeUndone the edits Vector is directly
accessed at indexOfNextAdd without any bounds checking:
{code:java}
@Override
protected UndoableEdtit editToBeUndone() {
int i = indexOfNextAdd;
while (i > 0) {
UndoableEdit edit = edits.elementAt(--i);
if (edit.isSignificant()) {
return edit;
}
}
return null;
}
{code}
For example editToBeRedone returns null in the case indexOfNextAdd >=
edit.size().
I assume the root cause to be the trimEdits method incorrectly updating the
indexOfNextAdd, possibly due to a negative value being passed from trimToLimits:
{code:java}
if (keepFrom < 0) {
keepTo -= keepFrom;
keepFrom = 0;
}
if (keepTo >= size) {
int delta = size - keepTo - 1;
keepTo += delta;
keepFrom += delta;
}
{code}
At least, the latter if doesn't ensure non-negative values for either keepTo or
keepFrom, which could cause the bug.
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