Re: Debugging crash in _class_shouldFinalizeOnMainThread
Re: Debugging crash in _class_shouldFinalizeOnMainThread
- Subject: Re: Debugging crash in _class_shouldFinalizeOnMainThread
- From: Greg Parker <email@hidden>
- Date: Wed, 1 Sep 2010 12:52:57 -0700
On Sep 1, 2010, at 11:15 AM, Barry Wark wrote:
> I'm getting intermittent crashes in my test suite for a GC application
> on OS X 10.6.4. The KERN_INVALID_ADDRESS at 0x0000000900000028 occurs
> in
>
> 0 libobjc.A.dylib 0x00007fff82ac847b
> _class_shouldFinalizeOnMainThread + 4
>
> within the Dispatch queue: Garbage Collection Work Queue thread.
>
> This application makes heavy use of third-party C++ libraries, so I
> assume that the problem is in my memory management of C++ within a GC
> app, but I'm not sure where to start the debugging process. Since GC
> is running on a separate thread, the debugger doesn't stop at a
> particularly useful place. Can anyone point me in a useful direction?
> I'd be happy to provide more details if there's relevant information
> I'm leaving out.
_class_shouldFinalizeOnMainThread() is called by the garbage collector on objects that it has decided are garbage. In this case, the dying object's isa pointer is invalid, and _class_shouldFinalizeOnMainThread() crashes while trying to dereference it.
It's likely that a memory smasher or use-after-free of some other object has clobbered this object's isa. Try running with guardmalloc and AUTO_USE_GUARDS=YES to see if those uncover a smasher somewhere.
--
Greg Parker email@hidden Runtime Wrangler
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