Do I have to use ->Release()?

I am work开发者_Python百科ing with a webbrowser host on c++, I managed to sink event and I am running this void on DISPID_DOCUMENTCOMPLETE:

void DocumentComplete(LPDISPATCH pDisp, VARIANT *url)
{
    READYSTATE rState;

    iBrowser->get_ReadyState(&rState);

    if(rState == READYSTATE_COMPLETE)
    {
        HRESULT hr;
        IDispatch *pHtmlDoc = NULL;
        IHTMLDocument2 *pDocument = NULL;
        IHTMLElement *pBody = NULL;
        IHTMLElement *lpParentElm = NULL;
        BSTR bstrHTMLText;

        hr = iBrowser->get_Document(&pHtmlDoc);

        hr = pHtmlDoc->QueryInterface(IID_IHTMLDocument2, (void**)&pDocument);

        if( (FAILED(hr)) || !pDocument)
        {
            MessageBox(NULL, "QueryInterface failed", "WebBrowser", MB_OK);
        }

        hr = pDocument->get_body( &pBody );

        if( (!SUCCEEDED(hr)) || !pBody)
        {
            MessageBox(NULL, "get_body failed", "WebBrowser", MB_OK);
        }

        pBody->get_parentElement(&lpParentElm);

        lpParentElm->get_outerHTML(&bstrHTMLText);

        _bstr_t bstr_t(bstrHTMLText);

        std::string sTemp(bstr_t);

        MessageBox(NULL, sTemp.c_str(), "WebBrowser", MB_OK);
    }
}

I don't much about c++, I built this code from watching other codes in google. Now I know I have to use ->Release, but do I have to use all these?:

    pHtmlDoc->Release();
    pDocument->Release();
    pBody->Release();
    lpParentElm->Release();
    iBrowser->Release();

Because on the examples I used to build my code it was using it only for the IHTMLElement(s).

Yes, you do have to call Release() on those pointers, otherwise objects will leak. The same goes for BSTRs.

You'll be much better off if you use smart pointers for that - ATL::CComPtr/ATL::CComBSTR or _com_ptr_t/_bstr_t.

You should wrap those objects into a CComPtr or one of its variants. That will handle the release for you. It goes with the concept of RAII.

Yes you do. But not on the iBrowser, you didn't acquire that pointer inside this code.

Beware that your error checking isn't sufficient, your code will bomb when get_Document() fails. Same for get_parentElement(). And after the message box is dismissed.