IXMLDOMDocument memory Leak Issue - visual-c++

Question

I have a COM inproc server test application that uses IXMLDOMDocument to write data and send it back to COM client.I uses get_xml() to get BSTR. But when applications ends it's consuming almost > 20 MB memory while if I don't use COM inproc server it uses < 1 MB.
My COM Server Interface method is
[
object,
uuid(BF798ED1-DCDD-4B29-B552-3A17F1D7E4CF),
dual,
nonextensible,
pointer_default(unique)
]
interface IMoLauncher : IDispatch{
[id(1)] HRESULT GetXML([out] BSTR* bStr);
};
it's code is
STDMETHODIMP CMoLauncher::GetXML(BSTR* bStr)
{
AFX_MANAGE_STATE(AfxGetStaticModuleState());
BOOL result = FALSE;
IXMLDOMDocument* pDoc = NULL;
HRESULT hr = CoCreateInstance(CLSID_DOMDocument, NULL, CLSCTX_INPROC_SERVER,
IID_IXMLDOMDocument, (void**)&pDoc);
if ( SUCCEEDED(hr) )
{
result = TRUE;
IXMLDOMNode* pEntityNode = InsertDOMElement(pDoc, NULL, L"Entity", NULL);
SerializeXML(pDoc, pEntityNode);
pDoc->get_xml(bStr);
pDoc->Release();
}
return result;
}
And usage code in client is
CoInitialize(NULL);
IMoLauncher* launcher = NULL;
IUnknown* unknown = NULL;
HRESULT result = CoCreateInstance(CLSID_MoLauncher,NULL,CLSCTX_INPROC_SERVER,IID_IMoLauncher,(void**)&launcher);
if(result==S_OK)
{
for(int i=0;i<iterationCount;i++)
{
BSTR bStr;
launcher->GetXML( &bStr);
printf("Iteration %d\n",i);
::SysFreeString(bStr);
}
}
launcher->Release();
CoUninitialize();

Answer 1

You Need to release pEntityNode too!
Every COM pointer returned by an Interface or COM function must be released. You may use smart pointers to avoid such mistakes.

Answer 2

The IXMLDOMNode* returned from CMoLauncher::InsertDOMElement is never released, that's a big leak.
You need to add Release calls for:
The first InsertDOMElement call in CMoLauncher::SerializeXML.
The InsertDOMElement calls in the loop in the same function (adding a local variable in order to do so (return value of InsertDOMElement)
The InsertDOMElement call in CMoLauncher::GetXML (spotted by xMRI)