CoReleaseMarshalData

Destroys a previously marshalled data packet.

STDAPI CoReleaseMarshalData(

IStream * pStm	//Stream containing data packet
);

Parameter
pStm

Points to the stream that contains the data packet which is to be destroyed.

Return Values
S_OK

Indicates the data packet was successfully destroyed.

STG_E_INVALIDPOINTER

Indicates an IStream error dealing with the pStm parameter.

CO_E_NOTINITIALIZED

Indicates that the CoInitialize or OleInitialize function was not called on the current thread before this function was called.

E_OUTOFMEMORY

Out of memory.

E_INVALIDARG

Indicates pStm is invalid.

E_UNEXPECTED

Indicates an unexpected error occurred.

E_FAIL

Indicates an unspecified error.

Comments
The main steps that CoReleaseMarshalData performs are the following:

The function reads a CLSID from the stream.
If standard marshalling is being used, the function gets an IMarshal pointer to an instance of the standard unmarshaller. If custom marshalling is being used, the function creates a proxy by calling the CoCreateInstance function, passing the CLSID it read from the stream, and requests an IMarshal interface pointer to the newly created proxy.
Using whichever IMarshal interface pointer it has acquired, the function calls IMarshal::ReleaseMarshalData.

You typically do not call this function. The only situation in which you might need to call this function is if you use custom marshalling (write and use your own implementation of IMarshal). Examples of when CoReleaseMarshalData should be called include the following situations:

An attempt was made to unmarshal the data packet, but it failed.
A marshalled data packet was removed from a global table.

As an analogy, the data packet can be thought of as a reference to the original object, just as if it were another interface pointer being held on the object. Like a real interface pointer, that data packet must be released at some point. The use of IMarshal::ReleaseMarshalData to release data packets is analogous to the use of IUnknown::Release to release interface pointers.

Note that you do not need to call CoReleaseMarshalData after a successful call of the CoUnmarshalInterface function; that function releases the marshal data as part of the processing that it does.