Re: COM Smart pointer doesn't keep its reference

From:

"Alex Blekhman" <xfkt@oohay.moc>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 8 Aug 2006 14:38:06 +0300

Message-ID:

<uhDpf8tuGHA.3500@TK2MSFTNGP06.phx.gbl>

"Igor Tandetnik" wrote:

// Returns the current member
CObj2* CCol2::getObj2(void)
{
   COMNamespace::_CCOMCol2Ptr pCOMCol2;
   COMNamespace::ICommonObjectPtr pDataObjPtr;
   COMNamespace::_CCOMObj2Ptr pCOMObjPtr;
   HRESULT hr;

   hr =
pCOMCol2.CreateInstance(__uuidof(COMNamespace::CCOMCol2));
   hr =
pCOMObjPtr.CreateInstance(__uuidof(COMNamespace::CCOMObj2));

   pDataObjPtr = m_pCollection->Item[m_lCurrent];

   hr =
pDataObjPtr.QueryInterface(__uuidof(COMNamespace::_CCOMObj2),
                    (void**) &pCOMObjPtr);

You are leaking a reference here. pCOMObjPtr already
stores an AddRef'ed COM pointer, but your QueryInterface
call would overwrite the old value without releasing it
first.

Actually, `operator &' of _com_ptr_t class will release
original raw pointer before returning its address. So, no
interface leak should happen here. However, calling
QueryInterface is redundant since `operator =' does it
already.