CoCreateInstance Returning E_INVALIDARG

Question

What I'm attempting to do here is simply create an instance of an interface. Really is supposed to be that simple. Been following any online material, and reading material I can find and can't solve this issue for the life of me.

It comes down to the HRESULT that comes back from CoCreateInstance being E_INVALIDARG. I've changed around the parameters as much as I can to try and get it to work but still can't get it. So please take a glance and hopefully someone can point out something simple I'm over looking.

//Instantiate the sink class and hold a pointer to it.
    m_pSink = new CSink();

    HRESULT hr = CoInitialize(NULL);

    //Get a pointer to sinks IUnknown, no AddRef. CMySink implements only
    //dispinterface and the IUnknown and IDispatch pointers will be same.
    LPUNKNOWN pUnkSink = m_pSink->GetIDispatch(FALSE); 

    CLSID clsidInterface;
    hr = CLSIDFromProgID(L"Automation.AutomationInterface", &clsidInterface);

    ICALib::IAutomationInterface *p_Interface = NULL;
    hr = CoCreateInstance(clsidInterface, NULL, CLSCTX_LOCAL_SERVER, ICALib::IID_IAutomationInterface, (void**)p_Interface);

    if (hr != S_OK) // Show a message box if the Instance of the interface is not created and do not create the object.
    {
        CMessageBox(CMessageBox::WARNING_OK).Show(IDS_WARNING_BADLICENSE);
        m_failedToCreate = TRUE;
        this->~CMainClass();
        return;
    }

    //Establish a connection between source and sink.
    //m_pUnkSrc is IUnknown of server obtained by CoCreateInstance().
    //m_dwCookie is a cookie identifying the connection, and is needed to terminate the connection.
    BOOL result = AfxConnectionAdvise(p_Interface, m_pSink->GetGUID(), pUnkSink, FALSE, &m_dwCookie);

(Actual names are not shown in this code due to Legal Liabilities)

Answer 1

You need to take the address of p_Interface and pass that to CoCreateInstance. As it is you're just passing a NULL pointer for the last argument.