Re: Do I need to call Release on smart pointer

From:

"jean" <jean.shu@gmail.com>

Newsgroups:

microsoft.public.vc.language

Date:

31 May 2006 15:59:34 -0700

Message-ID:

<1149116374.311960.226020@y43g2000cwc.googlegroups.com>

One last question. In case if I forgot to call Release, is there a tool
to detect it before it cause problem, can I use tools for detecting
memory leak for this? Thanks.
Jeff Partch [MVP] wrote:

"jean" <jean.shu@gmail.com> wrote in message
news:1149098412.698243.183080@y43g2000cwc.googlegroups.com...

Hi,

I have the following question. Thanks.
1. How do I figure out if a Microsoft SDK function return AddRef'd
pointers, e.g GetHtmlDocument()?

I'm inclined to say that if the documentation does not say something like,
"returns a non-AddRef'd interface pointer", then start with the premise that
it is AddRef'd. If your GetHtmlDocument is my GetHtmlDocument than it does
return an AddRef'd pointer.

2. What's the consequence if I don't call Release? Is it memory leak? I

The internal reference count will remain higher than it should and the
object will presumably live forever like Arvin Sloane. This will indeed
waste memory.

have the following code using GetHtmlDocument(), but I didn't use
Release, the program runs fine.

It probably won't cause immediate failure. Worst case, there's just an
orphaned object sitting in memory. You'd have to have a considerable few of
them left abandoned before things started failing.

IHTMLDocument2 *document;
LPDISPATCH lpDispatch = GetHtmlDocument();
ASSERT(lpDispatch);
//get html document from IDispatch
LRESULT hr=lpDispatch->QueryInterface(IID_IHTMLDocument2, (void**)
&document);

WriteToDocument( document, xmlStr );

IMO, you should do it more like...

LPDISPATCH lpDispatch = GetHtmlDocument();
if (lpDispatch)
{
    //get html document from IDispatch
    IHTMLDocument2* document = NULL;
    HRESULT hr = lpDispatch->QueryInterface(IID_IHTMLDocument2,
(void**)&document);
    if (SUCCEEDED(hr) && (document))
    {
        WriteToDocument(document, xmlStr);
        document->Release();
    }
    lpDispatch->Release();
}

--
Jeff Partch [VC++ MVP]