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Re: Exception at WinNativeHelper under Windows

After looking for programers having the same problem in the archives of this
mailing list, I found no solution had been given here (am I wrong ?).

So if you have this Exception (only with Windows (2000 and 98 at least), Mac
users you are not concerned...):

An unexpected exception has been detected in native code outside the VM.
Unexpected Signal : EXCEPTION_ACCESS_VIOLATION occurred at PC=0x66A0CF42
(...)

Current Java thread:
at quicktime.WinNativeHelper.freeDrawingSurface(Native Method)
at quicktime.WinJNIDrawingSurface.finalize(WinJNIDrawingSurface.java:47)
at java.lang.ref.Finalizer.invokeFinalizeMethod(Native Method)
at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:83)
at java.lang.ref.Finalizer.access$100(Finalizer.java:14)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:160)

Here is how I fixed the trouble:
it seems that it occurs if your program execute QTsession.open() from within a
JFrame's constructor (there could be a link with Swing) if your main class
extends JFrame for example...
If you want to avoid this, you must execute QTsession.open() from another
method (I personnaly use an event method to do so, and it actually works !).

Very interesting, and very well timed! I've just started seeing this in my code when running under Virtual PC. Sometimes it's fine, sometimes it crashes consistently. From the look of the stack trace, there seems to be a race state and it all depends on how lucky or unlucky you are regarding when the JVM finalizer thread happens to run.

This is similar, but not the same, as another problem I've recently experienced under OS X. I've been getting very infrequent random crashes when doing certain heavy QTJava processing, which I'm almost certain is due to the garbage collector kicking in and disposing some QT objects. QuickTime isn't re-entrant and a crash can occur if QTObject.finalize() is called while another thread is invoking QuickTime. I fixed my particular problem by enclosing the entire process in

synchronized(QTSession.terminationLock())
{
...
}

This has the disadvantage of blocking any QT objects from being freed up in that block so you may need to take care if you're allocating lots of things. I can't know 100% for sure but I haven't had any random crashes since then :-)

-Rolf
--
Rolf Howarth, Square Box Systems Ltd, Stratford-upon-Avon UK.
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References: 
 >Exception at WinNativeHelper under Windows (From: "Laurent BURY" <email@hidden>)



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