CoReleaseMarshalData function (combaseapi.h)

Destroys a previously marshaled data packet.


HRESULT CoReleaseMarshalData(
  [in] LPSTREAM pStm


[in] pStm

A pointer to the stream that contains the data packet to be destroyed. See IStream.

Return value

This function can return the standard return values E_FAIL, E_INVALIDARG, E_OUTOFMEMORY, and E_UNEXPECTED, as well as the following values.

Return code Description
The data packet was successfully destroyed.
An error related to the pStm parameter.
The CoInitialize or OleInitialize function was not called on the current thread before this function was called.



Security Note: Calling this method with untrusted data is a security risk. Call this method only with trusted data.

The CoReleaseMarshalData function performs the following tasks:
  1. The function reads a CLSID from the stream.
  2. If COM's default marshaling implementation is being used, the function gets an IMarshal pointer to an instance of the standard unmarshaler. If custom marshaling 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.
  3. 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 marshaling (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 marshaled 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.

Important  You must call the CoReleaseMarshalData function in the same apartment that called CoMarshalInterface to marshal the object into the stream. Failure to do this may cause the object reference held by the marshaled packet in the stream to be leaked.


Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps | UWP apps]
Minimum supported server Windows 2000 Server [desktop apps | UWP apps]
Target Platform Windows
Header combaseapi.h (include Objbase.h)
Library Ole32.lib
DLL Ole32.dll

See also