Should I IUnknown::Release interfaces created with DllGetClassObject

I'm trying to debug some code that uses COM, which I am a beginner at. The two calls to IUnknown::Release at the end have got me worried. The interfaces were created with DllGetClassObject and IClassFactory::CreateInstance. I have seen other similar code that does not call IUnknown::Release on these - which is correct?

int OpenMixer_Win_DirectSound(px_mixer *Px, int index)
{
   DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_DATA desc;
   HMODULE hDsound = INVALID_HANDLE_VALUE;
   GCO DllGetClassObject;
   IClassFactory *pcf = NULL;
   IKsPropertySet *pps = NULL;
   HRESULT hr;
   ULONG bytes;
   LPGUID guidIn;
   LPGUID guidOut;
   UINT deviceIn = -1;
   UINT deviceOut = -1;
   int ret = FALSE;

   guidIn = PaWinDS_GetStreamInputGUID(Px->pa_stream);
   guidOut = PaWinDS_GetStreamOutputGUID(Px->pa_stream);

   do {
      hDsound = LoadLibraryA("dsound.dll");
      if (hDsound == NULL) {
         break;
      }

      DllGetClassObject = (GCO) GetProcAddress(hDsound, "DllGetClassObject");
      if (DllGetClassObject == NULL) {
         break;
      }
      hr = DllGetClassObject(&开发者_JS百科CLSID_DirectSoundPrivate,
                             &IID_IClassFactory,
                             (void **)(&pcf));
      if (hr || pcf == NULL) {
         break;
      }

      hr = IClassFactory_CreateInstance(pcf,
                                        NULL,
                                        &IID_IKsPropertySet,
                                        (void **)(&pps));
      if (hr || pps == NULL) {
         break;
      }

      /* Do stuff with the interfaces */

   } while( FALSE );

   if (pps) {
      IUnknown_Release(pps);
   }

   if (pcf) {
      IUnknown_Release(pcf);
   }

   // Free the library.  Note that portaudio also opens dsound.dll
   // so this probably doesn't do anything until Pa_Terminate is called.
   if (hDsound != INVALID_HANDLE_VALUE) {
      FreeLibrary(hDsound);
   }
}

Absolutely. Both functions create a new interface pointer, they will have a reference count of 1, the AddRef() function was already called. When you're done with it then you have to call Release(). You'll leak memory if you don't. Every interface in COM works this way.

Yes. As seen in DllGetClassObject sample, the return ppvObj will have a refcount.

Yes, DllGetClassObject() will create an object and pass ownership of that object to your code. Your code will now own the object and be responsible for releasing it by calling IUnknown::Release().