Pluggable Protocol not released (?)

Question

Hi,
I have an MFC application which uses CHtmlView (WebBrowser control) to display HTML data. For displaying, I implemeted an asynchronous pluggable protocol. I did this by adding ATL support to my MFC project and adding an OLE class derived from IInternetProtocol
and IInternetProtocolInfo to my project (using the wizard). My pluggable protocol is defined as follows:
class ATL_NO_VTABLE CPluggableProtocol :
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CPluggableProtocol, &CLSID_PluggableProtocol>,
public IInternetProtocol,
public IInternetProtocolInfo
public:
CPluggableProtocol()
: m_fData(MEMORY_BUFFER)
DECLARE_REGISTRY_RESOURCEID(IDR_PLUGGABLEPROTOCOL)
BEGIN_COM_MAP(CPluggableProtocol)
COM_INTERFACE_ENTRY(IInternetProtocolInfo)
COM_INTERFACE_ENTRY(IInternetProtocol)
END_COM_MAP()
DECLARE_PROTECT_FINAL_CONSTRUCT()
HRESULT FinalConstruct()
return S_OK;
void FinalRelease()
// IInternetProtocol interface
public:
STDMETHOD(Start)(
LPCWSTR szUrl,
IInternetProtocolSink *pIProtSink,
IInternetBindInfo *pIBindInfo,
DWORD grfSTI,
DWORD dwReserved);
STDMETHOD(Continue)(PROTOCOLDATA *pStateInfo);
STDMETHOD(Abort)(HRESULT hrReason,DWORD dwOptions);
STDMETHOD(Terminate)(DWORD dwOptions);
STDMETHOD(Suspend)();
STDMETHOD(Resume)();
STDMETHOD(Read)(void *pv,ULONG cb,ULONG *pcbRead);
STDMETHOD(Seek)(
LARGE_INTEGER dlibMove,
DWORD dwOrigin,
ULARGE_INTEGER *plibNewPosition);
STDMETHOD(LockRequest)(DWORD dwOptions);
STDMETHOD(UnlockRequest)();
// IInternetProtocolInfo interface
public:
STDMETHOD(CombineUrl)(LPCWSTR pwzBaseUrl, LPCWSTR pwzRelativeUrl, DWORD dwCombineFlags,
LPWSTR pwzResult, DWORD cchResult, DWORD *pcchResult, DWORD dwReserved);
STDMETHOD(CompareUrl)(LPCWSTR pwzUrl1, LPCWSTR pwzUrl2, DWORD dwCompareFlags);
STDMETHOD(ParseUrl)(LPCWSTR pwzUrl, PARSEACTION ParseAction, DWORD dwParseFlags,
LPWSTR pwzResult, DWORD cchResult, DWORD *pcchResult, DWORD dwReserved);
STDMETHOD(QueryInfo)( LPCWSTR pwzUrl, QUERYOPTION QueryOption, DWORD dwQueryFlags,
LPVOID pBuffer, DWORD cbBuffer, DWORD *pcbBuf, DWORD dwReserved);
private:
CAtlStringW GetContentType(CString &);
CMemFile m_fData;
In my InitInstance I register this protocol using RegisterNameSpace (and UnregisterNameSpace in ExitInstance). This is done by the following:
CComPtr<IClassFactory> m_spCF; // (class member)
CComPtr<IInternetSession> spIInetSession;
if(FAILED(CoInternetGetSession(0, &spIInetSession, 0)))
return FALSE;
HRESULT hr;
if(FAILED(CPluggableProtocol::_ClassFactoryCreatorClass::CreateInstance(CPluggableProtocol::_CreatorClass::CreateInstance, IID_IClassFactory, reinterpret_cast<void**>(&m_spCF))))
return FALSE;
hr = spIInetSession->RegisterNameSpace(m_spCF, CLSID_PluggableProtocol, m_strProtocol, 0, NULL, 0);
This works on all the computers I have access to and it worked for a few months no. No problems.
But now I got the message from somebody using the application that the application does not terminate. Using logfiles I found out that AfxOleCanExitApp() returns TRUE in CMainFrame::OnNcDestroy. This means that not all COM objects have been released and
therefore the application does not quit (only the windows disappear). Using the debugger (breakpoint at AfxOleLockApp()), I found out that the one COM object which is calling AfxOleLockApp is the asynchronous pluggable protocol (through urlmon.dll).
Unfortunately I can not do trial and error because it works perfectly on all my computers. But since it does obviously not work for a different person I am sure I have a little mistake in my implementation. I have very few COM experience, therefore it may
be that the code above is not perfectly correct.
Does anybody see a mistake in my implementation which could cause the bug?
Thank you very much,
Peter

Answer 1

Hello,
Hmm, no idea? :-(
Another thing which came into my mind:
I call RegisterNameSpace in InitInstance and UnregisterNameSpace in ExitInstance. However, ExitInstance is called
after receiving WM_QUIT, bevor the MFC framework asks via AfxOleCanExitApp() if it will call PostQuitMessage().
Maybe I must do this stuff in the window function? E.g. RegisterNameSpace on WM_CREATE and UnregisterNamespace on WM_CLOSE? This would be before the AfxOleCanExitApp() check...
And: After I cann UnregisterNameSpace, can I be sure that all COM objects are destroyed and released?
Regards, Peter