Advise of Connection Point calls QueryInterface with IID_IMarshal - c++

Question

I am trying to build Connection Points in existing COM component. I derive the class from CCmdTarget and call MFC macros in class declaration and implementation as described in MSDN. Component is correctly build, linked, and run. However, when I debug my client application I see the following issue:
Client locates the correct component, finds the connection point container and appropriate connection point; however Advise method fails to establish connection.
It is assumed that this Advise calls the QueryInterface with IID__IAdHocPresenceEvents.
Do not understand why this calls the QueryInterface with IID_IMarshal.
Later this becomes reason for not getting event at ClientSink::OnAdHocPresenceQuery
So, please help me to resolve this issue or give a hint where else to look for the issue.
Thanks in advance,
Hovo
class ClientSink : public _IAdHocPresenceEvents
{
private:
DWORD m_dwRefCount;
public:
ClientSink();
virtual ~CClientSink();
STDMETHODIMP OnAdHocPresenceQuery(int Result)
{
CString strTemp ("OnAdHocPresenceQuery");
AfxMessageBox(strTemp);
return S_OK;
};
HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void **ppvObject)
{
HRESULT hr = S_OK;
if (iid == IID_IUnknown)
{
m_dwRefCount++;
*ppvObject = (IUnknown *)this;
}
else if (iid == IID__IAdHocPresenceEvents)
{
m_dwRefCount++;
*ppvObject = (_IAdHocPresenceEvents *)this;
}
else
{
*ppvObject = NULL;
hr = E_NOINTERFACE;
}
return hr;
}
ULONG STDMETHODCALLTYPE AddRef()
{
m_dwRefCount++;
return m_dwRefCount;
}
ULONG STDMETHODCALLTYPE Release()
{
ULONG l;
l = m_dwRefCount--;
if ( 0 == m_dwRefCount)
{
delete this;
}
return l;
}
};
int SendRequest()
{
CLSID clientCLSID;
if (FAILED(CLSIDFromProgID(A2BSTR("SMC.SMCLink"), &clientCLSID)))
{
clientCLSID = SMC::CLSID_SMCLink;
}
LPUNKNOWN lpUnk;
SMC::ISMCLink* m_pSMCLink = NULL;
if (m_pSMCLink == NULL)
{
if (GetActiveObject(clientCLSID, NULL, &lpUnk) == NOERROR)
{
hr = lpUnk->QueryInterface(SMC::IID_ISMCLink, (LPVOID*)&m_pSMCLink);
lpUnk->Release();
}
}
if(hr != S_OK)
{
return -1;
}
DWORD dwAdvise = 0; //variable,shown here for completeness
IConnectionPoint *pCntPoint = NULL;
IConnectionPointContainer *pConnPtContainer = NULL;
//check if this interface supports connectible objects
hr = m_pSMCLink->QueryInterface(IID_IConnectionPointContainer,(void **)&pConnPtContainer);
if ( !SUCCEEDED(hr) )
{
return hr;
}
// find the specific connection point
hr = pConnPtContainer->FindConnectionPoint(IID__IAdHocPresenceEvents, &pCntPoint);
if ( !SUCCEEDED(hr) )
{
return hr;
}
//we are done with the connection point container interface
pConnPtContainer->Release();
IUnknown *pSinkUnk = NULL;
CSink *pSink = NULL;
pSink = new CSink;
if ( NULL == pSink )
{
return E_FAIL;
}
//Get the pointer to CSink's IUnknown pointer
hr = pSink->QueryInterface (IID_IUnknown,(void **)&pSinkUnk);
if ( !SUCCEEDED(hr) )
{
return hr;
}
// It is assumed that this should call the QueryInterface with IID__IAdHocPresenceEvents
// Do not understand why this calls the QueryInterface with IID_IMarshal
// Later this becomes reason for not getting event at ClientSink::OnAdHocPresenceQuery
hr = pCntPoint->Advise(pSinkUnk, &dwAdvise);
if ( !SUCCEEDED(hr) )
{
return hr;
}
hr = m_pSMCLink->RequestService(BSTR("hov#moco"));
pCntPoint->Unadvise(dwAdvise); //disconnect from server
pCntPoint->Release();
return hr;
}
[
helpstring("Interface to control My Product"),
uuid(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx),
dual,
oleautomation
]
interface ISMCLink : IDispatch
{
// ...
HRESULT RequestService([in] BSTR user);
// ...
};
// Primary dispatch interface for My Component
[ uuid(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) ]
dispinterface IDispSMCLink
{
interface ISMCLink;
};
[
helpstring("ISMCLink2, Interface to access My Product"),
uuid(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx),
dual,
oleautomation
]
interface ISMCLink2 : ISMCLink
{
//..
};
[ uuid(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx), version(1.0) ]
library SMC
{
importlib("stdole32.tlb");
importlib("stdole2.tlb");
[
uuid(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx),
helpstring("_IAdHocPresenceEvents Interface")
]
interface _IAdHocPresenceEvents : IUnknown
{
[id(1), helpstring("method OnAdHocPresenceQuery")] HRESULT OnAdHocPresenceQuery(int Result);
};
#include "ISMCLink.idl"
[ uuid(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) ]
coclass SMCLink
{
dispinterface IDispSMCLink;
[default] interface ISMCLink;
interface ISMCLink2;
[default, source] interface _IAdHocPresenceEvents;
};
};
class SMCLink : public CCmdTarget
{
protected:
DECLARE_MESSAGE_MAP()
DECLARE_DISPATCH_MAP()
DECLARE_INTERFACE_MAP()
// Connection point for ISMCLink interface
BEGIN_CONNECTION_PART(SMCLink, AdHocPresenceEvents)
CONNECTION_IID(IID__IAdHocPresenceEvents)
END_CONNECTION_PART(AdHocPresenceEvents)
DECLARE_CONNECTION_MAP()
public:
SMCLink(void);
virtual ~SMCLink(void);
// to be OLE creatable, it must be DYNCREATE and OLECREATE
DECLARE_DYNCREATE(SMCLink)
DECLARE_OLECREATE(SMCLink)
// Generated OLE dispatch map functions
//{{AFX_DISPATCH(SMCLink)
afx_msg HRESULT RequestAdHocPresence(BSTR sipAddr);
//}}AFX_DISPATCH
BEGIN_DUAL_INTERFACE_PART(DualSMCLink, ISMCLink)
//..
STDMETHOD(RequestService)(THIS_ BSTR user);
END_DUAL_INTERFACE_PART(DualSMCLink)
};
//..
BEGIN_MESSAGE_MAP(SMCLink, CCmdTarget)
//{{AFX_MSG_MAP(CAutoProxy)
// NOTE - the ClassWizard will add and remove mapping macros here.
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
IMPLEMENT_DYNCREATE(SMCLink, CCmdTarget)
BEGIN_DISPATCH_MAP(SMCLink, CCmdTarget)
//{{AFX_DISPATCH_MAP(SMCLink)
//..
DISP_FUNCTION(SMCLink, "RequestService", RequestService, VT_ERROR, VTS_BSTR)
//}}AFX_DISPATCH_MAP
END_DISPATCH_MAP()
BEGIN_INTERFACE_MAP(SMCLink, CCmdTarget)
INTERFACE_PART(SMCLink, IID_ISMCLink, DualSMCLink)
INTERFACE_PART(SMCLink, IID_ISMCLink2, DualSMCLink)
INTERFACE_PART(SMCLink, IID_IConnectionPointContainer, ConnPtContainer)
END_INTERFACE_MAP()
BEGIN_CONNECTION_MAP(SMCLink, CCmdTarget)
CONNECTION_PART(SMCLink, IID__IAdHocPresenceEvents, AdHocPresenceEvents)
END_CONNECTION_MAP()
SMCLink::SMCLink(void)
{
// enable this object for OLE automation
EnableAutomation();
// enable this object for connection points
EnableConnections();
}
//..
afx_msg HRESULT SMCLink::RequestService(BSTR sipAddr)
{
HRESULT hr = E_FAIL;
int status = 1;
const CPtrArray* pConnections = m_xAdHocPresenceEvents.GetConnections ();
ASSERT (pConnections != NULL);
int nConnections = pConnections->GetSize ();
if (nConnections) {
for (int i=0; i<nConnections; i++)
{
_IAdHocPresenceEvents* pInterface = (_IAdHocPresenceEvents*) (pConnections->GetAt (i));
ASSERT (pInterface != NULL);
// Outgoing!
hr = pInterface->OnAdHocPresenceQuery (status);
}
}
return hr;
}
// delegate standard IDispatch methods to MFC IDispatch implementation
DELEGATE_DUAL_INTERFACE(SMCLink, DualSMCLink)
STDMETHODIMP SMCLink::XDualSMCLink::RequestService(BSTR user)
{
METHOD_PROLOGUE(SMCLink, DualSMCLink)
return pThis->RequestService(user);
}
//..

Answer 1

IMarshal is queried because COM needs to marhsal the calls between processes. While you can obviously implement the interface yourself, there is no point in bothering with this. Instead, make sure your interface is OLE Automation compatible, and is on a type library and the type library is registered (you can check this with COM/OLE Viewer tool. COM will supply automatic proxy/stub pair for you and won't require that IMarshal is implemented.