Re: getting a com interface from an out of process erver

"Igor Tandetnik" <>
Fri, 7 Aug 2009 20:32:57 -0400
Drew Hohmann <> wrote:

I am creating an instance of an object, then one of the methods of the
object will return an instance to a different object (similar to how
the windows media player com interface works, see
IWMReaderAccelerator::GetCodecInterface for an example).

Note that IWMReaderAccelerator is not automation-compatible.

In process this works fine, but out of process it appears that neither
the IID or the pointer are being marshaled correctly. I did notice
 that according to the oleautomation attribute documentation, GUID's
are not one of the types listed as automation compatible (nor are

VARIANTs are automation compatible. GUIDs are not. Most automation
clients only know how to use IDispatch anyway, and have no need for

I'd be willing to give up the guid, as long as I
could get the IUnknown ** to work.

IUnknown should work. You must be doing something wrong.

//idl code
helpstring("IT1 Interface"),
interface IT1 : IDispatch{
  [id(1), helpstring("method GetTClass")] HRESULT GetTClass([in]
REFIID riid, [out] IUnknown** tclass);

This is certainly not an automation-compatible method, and won't marshal
correctly using TLB-driven marshalling.
With best wishes,
    Igor Tandetnik

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