RFR: 8079136: Accessing a nested sublist leads to StackOverflowError
ivan.gerasimov at oracle.com
Tue May 5 08:58:07 UTC 2015
Thank you Daniel for taking look at it!
On 05.05.2015 11:14, Daniel Fuchs wrote:
> Hi Ivan,
> Have you considered to simply override/change subList(int fromIndex,
> int toIndex)
> in SubList and RandomAccessSubList - so that 'l'/'parent' points
> always to the original
> root list (instead of being a sublist of sublist of sublist)?
With this fix, both SubList and RandomAccessSubList are made private
inner classes of AbstractList.
So now we have a pointer to the original root list, which is
AbstractList.this in addition to the parent field.
All the access methods are implemented to call the corresponding methods
of this root list.
However, we still need to keep a reference to the immediate parent
(which might also be a sublist).
When the leaf sublist is modified, its modCount and size fields are
The same adjustment has to be done to all the members of the sublist chain.
> It seems to me that overriding sublist to create a sublist based on
> 'l'/'parent' instead of basing it on 'this' would solve the same problem
> with much less modifications... Or am I maybe missing something?
We have to keep both references: one to the root list, and the other to
the immediate parent list.
The first reference is used to pass the access requests.
The second is used to maintain modCount and size fields of all the
sublists in the chain.
> best regards,
> -- daniel
> On 5/5/15 9:17 AM, Ivan Gerasimov wrote:
>> When creating a sublist with List.subList(), it keeps a reference to
>> its parent.
>> Then, when accessing (get(), set(), add(), remove(), etc.) the
>> sublist, it recursively calls the corresponding methods of its parent.
>> This recursion, when deep enough, can cause StackOverflowError.
>> The only reason to do things recursively here, is the need to update
>> modCount and size of all the parents.
>> So, the proposal is to update these fields in a loop.
>> A few cleanups were done along the way.
>> Would you please help review the fix?
>> BUGURL: https://bugs.openjdk.java.net/browse/JDK-8079136
>> WEBREV: http://cr.openjdk.java.net/~igerasim/8079136/0/webrev/
>> Sincerely yours,
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