[vtkusers] Delete problems

David Cole david.cole at kitware.com
Fri Jul 14 16:27:42 EDT 2006

Can you set a breakpoint on this message in the VTK code and then send 
the call stack to the list? This means that an object *other* than one 
that has a legitimate reference to it is actually trying to delete it. 
Your program is trying to forcibly delete something *prior* to when the 
last referencer has let go of the object.....

Dominik Szczerba wrote:

> Thanks a lot, I am doing all this, still with no success:
> "Trying to delete object with non-zero reference count."
> Indeed, if I print the reference count it is never zero. So does the 
> delete order really not matter? If I can only delete non-zero counted 
> objects, then I cannot delete anything! Are the children not deleted 
> automatically or something?
> regards
> Dominik
> David Cole wrote:
>> Any "New" calls should have corresponding "Delete" calls. Any 
>> "Register" calls should have corresponding "UnRegister" calls. And 
>> any reference loops need to be broken by setting one of the pointer 
>> variables involved to NULL or 0.
>> Order is largely irrelevant except in the reference loop case. 
>> Sometimes it's important to know which part of a reference loop needs 
>> to go away first. Perhaps you need to force a bunch of objects to go 
>> away before a window is destroyed (for example).
>> That's the beauty of reference counted systems: order doesn't matter 
>> as much as balance does...
>> If you can't figure out where there's a missing Delete or UnRegister 
>> call, look for loops in pointer members (does your pipeline have a 
>> feedback loop??) It sometimes helps to draw a diagram of the 
>> pipeline. Or you could try simplifying it bit by bit and see when the 
>> leak goes away... Then start adding things back in until the leak 
>> comes back. That should point out where to look in the code...
>> Hope this helps,
>> David
>> Dominik Szczerba wrote:
>>> Hi,
>>> I have a quite complex pipeline with a few actors and filters. When 
>>> I clean up at the end I always get a non-zero reference count 
>>> somewhere (using C++). How do I robustly know in which order I 
>>> should Delete my components?
>>> PS. this is particularly annoying in combination matlab-vtk, as 
>>> matlab dies on any of such errors.
>>> regards,
>>> Dominik
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