Memory leaks with unamaneged com objects

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Calm Interop - 11 Sep 2003 07:07 GMT

Hi,

I am getting a strange scenario where I am using RCWs for
CDO and ADO in my managed classes. When the managed
objects get destructed, it seems the referenced unmanaged
resources are stacking up in memory for ever.

Does'nt GC take of those too? Please note that I am using
these unmanaged object references in method level in
managed classes, but not at class level.

I have tried Marshal.ReleaseComObject method to
explicitly detroy the memory trace of the com object, but
there is no improvement noticed in memory usage by CPU,
and getting higher every minute.

Please let me know how to dispose unmanaged objects at
method level ? (The exact and right way indeed.)

Regards
Tom

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Michael Green - 16 Sep 2003 01:08 GMT

Tom,

Unmanaged objects are not garbage collected. The garbage collector has no
knowledge of anything that is unmanaged. Your managed wrappers will get
garbage collected, but not the objects they reference. You will need to
explicitly release the unmanaged objects for them to get cleaned up. You
should be able to do this by calling IUnknown::Release on them.

I hope this is helpful,

Thanks,

Michael Green
Microsoft Developer Support

This posting is provided "AS IS" with no warranties, and confers no rights.
Please reply to newsgroups only.

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David Browne - 16 Sep 2003 23:38 GMT

> Tom,
>
[quoted text clipped - 3 lines]
> explicitly release the unmanaged objects for them to get cleaned up. You
> should be able to do this by calling IUnknown::Release on them.

Actually, not so. COM interop isn't _that_ broken.

After the Runtime Callable Wrapper for the COM object is garbage collected,
it's finalizer will decrement the reference count on the COM interface. The
COM object will normally be destroyed at that point.

This may be a long time after you wanted the object to be destroyed, so you
can call

Marshal.ReleaseComObject()

To destroy the com object before you let the RCW go out of scope.

David

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Memory leaks with unamaneged com objects

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