Passing SAFEARRAY of SHORTs in event causes EEMessageException

Bjoern <>
Thu, 29 Nov 2007 09:42:55 -0800 (PST)

I'm trying to pass a short array (of audio samples) in an event
of an ATL object but when I invoke the interface an
EEMessageException is thrown. Here's how the event-interface is

dispinterface IMyAudioEvents
  [id(1), helpstring("")] void OnUserAudioData([in] LONG nUserID, [in]
LONG nSampleRate, [in] SAFEARRAY(SHORT) pRawAudio, [in] LONG

Here's what the generated event-interface looks like after I compile
the .IDL. Note, however, that I had to change the type of the
SAFEARRAY(SHORT) to SAFEARRAY*. Please correct me if this type isn't
right. I remember reading a post where another user had done

template<class T>
class CProxyIMyAudioEvents :
    public IConnectionPointImpl<T, &__uuidof(IMyAudioEvents)>
HRESULT Fire_OnUserAudioData( LONG nUserID, LONG nSampleRate,
SAFEARRAY* pRawAudio, LONG nSamples)
    HRESULT hr = S_OK;
    T * pThis = static_cast<T *>(this);
    int cConnections = m_vec.GetSize();
    for (int iConnection = 0; iConnection < cConnections; iConnection++)
        CComPtr<IUnknown> punkConnection = m_vec.GetAt(iConnection);
        IDispatch * pConnection = static_cast<IDispatch
        if (pConnection)
            CComVariant avarParams[4];
            avarParams[3] = nUserID;
            avarParams[3].vt = VT_I4;
            avarParams[2] = nSampleRate;
            avarParams[2].vt = VT_I4;
            avarParams[1] = pRawAudio;
            avarParams[0] = nSamples;
            avarParams[0].vt = VT_I4;
            DISPPARAMS params = { avarParams, NULL, 4, 0 };
            hr = pConnection->Invoke(1, IID_NULL, LOCALE_USER_DEFAULT,
    return hr;

I've also noticed in the above code that avarParams[1] isn't assigned
a type. I've tried to set the type to (VT_I2 | VT_SAFEARRAY) but it
didn't change anything. It still throws the EEMessageException.

Here's how I create the SAFEARRAY and invoke the

LRESULT EventHandler::Event_OnUserAudioData(UINT uMsg, WPARAM wParam,
LPARAM lParam, BOOL& bHandled)
    bHandled = TRUE;
    Talk* talk = reinterpret_cast<Talk*> (lParam);
            CComSafeArray<SHORT, VT_I2> safeArray;
                safeArray.Add(talk->samples, talk->rawAudio, FALSE);

            SAFEARRAY* pSA = safeArray;
            m_pEventInterface->Fire_OnUserAudioData(talk->userid, talk-
samplerate, pSA, talk->samples);
    return TRUE;

The above class (EventHandler) is based on ATL's CWindowImpl since I
have multiple threads in my application and my ATL object is Apartment
threaded. I call the Event_OnUserAudioData(..) method through
SendMessage(..) (so threading doesn't get screwed up).

Why is the EEMessageException thrown when pConnection->Invoke(..) is
called in CProxyIMyAudioEvents::Fire_OnUserAudioData(..)? I figure
it's either because of the way I declare the SAFEARRAY in the IDL
interface or the way I create the CComSafeArray.

I hope someone is able to help out.

-- Bjoern

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