CoUnmarshalInterface function (combaseapi.h)

Initializes a newly created proxy using data written into the stream by a previous call to the CoMarshalInterface function, and returns an interface pointer to that proxy.


HRESULT CoUnmarshalInterface(
  [in]  LPSTREAM pStm,
  [in]  REFIID   riid,
  [out] LPVOID   *ppv


[in] pStm

A pointer to the stream from which the interface is to be unmarshaled.

[in] riid

A reference to the identifier of the interface to be unmarshaled. For IID_NULL, the returned interface is the one defined by the stream, objref.iid.

[out] ppv

The address of pointer variable that receives the interface pointer requested in riid. Upon successful return, *ppv contains the requested interface pointer for the unmarshaled interface.

Return value

This function can return the standard return value E_FAIL, errors returned by CoCreateInstance, and the following values.

Return code Description
The interface pointer was unmarshaled successfully.
pStm is an invalid pointer.
The CoInitialize or OleInitialize function was not called on the current thread before this function was called.
The object application has been disconnected from the remoting system (for example, as a result of a call to the CoDisconnectObject function).
An error occurred reading the registration database.
The final QueryInterface of this function for the requested interface returned E_NOINTERFACE.



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

The CoUnmarshalInterface function performs the following tasks:
  1. Reads from the stream the CLSID to be used to create an instance of the proxy.
  2. Gets an IMarshal pointer to the proxy that is to do the unmarshaling. If the object uses COM's default marshaling implementation, the pointer thus obtained is to an instance of the generic proxy object. If the marshaling is occurring between two threads in the same process, the pointer is to an instance of the in-process free threaded marshaler. If the object provides its own marshaling code, CoUnmarshalInterface calls the CoCreateInstance function, passing the CLSID it read from the marshaling stream. CoCreateInstance creates an instance of the object's proxy and returns an IMarshal interface pointer to the proxy.
  3. Using whichever IMarshal interface pointer it has acquired, the function then calls IMarshal::UnmarshalInterface and, if appropriate, IMarshal::ReleaseMarshalData.
The primary caller of this function is COM itself, from within interface proxies or stubs that unmarshal an interface pointer. There are, however, some situations in which you might call CoUnmarshalInterface. For example, if you are implementing a stub, your implementation would call CoUnmarshalInterface when the stub receives an interface pointer as a parameter in a method call.


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