<AWT Dev> Review request for 8165829: Android Studio 2.x crashes with NPE at sun.lwawt.macosx.CAccessibility.getAccessibleIndexInParent

[Anton Tarasov]

On 9/15/2016 12:45 PM, Anton Tarasov wrote:
> Hello,
>
> Please review the fix:
>
> bug: https://bugs.openjdk.java.net/browse/JDK-8165829
> webrev: http://cr.openjdk.java.net/~ant/JDK-8165829/jdk9/webrev.0 
> <http://cr.openjdk.java.net/%7Eant/JDK-8165829/jdk9/webrev.0>
>
> (The bug is currently closed as “not an issue”, which is not quite 
> true. So once and if the fix is approved I can take the ownership of 
> the bug).
>
> The problem is this. Sometimes when a frame is closed there may appear 
> a race condition:
>
> - removeNotify() is called on the frame on EDT and it removes all the 
> events associated with the frame from the event queue.
>
> - The frame is requested by accessibility via the CAccessibility 
> static methods (like CAccessibility.getAccessibleIndexInParent). Those 
> methods are called from native on AppKit thread and they perform via 
> invokeAndWait. The latter is wrapped with an InvocationEvent whose 
> source is set to the frame. But, once the event is put on the event 
> queue, it's purged by the removeNotify() call. As the result, 
> invokeAndWait returns null. Then, in some of the mentioned methods 
> 'null' is unboxed to a primitive 'int' or 'boolean' which results in 
> NPE propagated to native. On the native side, the NPE is not properly 
> handled and is just re-thrown.

I forgot to add, as a comment to the fix, that createWithAccessible() is 
ok to return nil, it's checked.

Anton.

>
> I don't have a simple and safe solution for the race. So, I suggest to 
> fix the NPE/crash at least.
>
> Thanks,
> Anton.
>
>