Re: Is this a memory leak?
PaulH <paul.heil@gmail.com> wrote:
I'm using an ATL COM object function as described below. My question
is: since GetString() returns a BSTR, do I need to do a
SysFreeString() on the returned value?
You are using smart wrappers. GetString does not in fact return BSTR: it
returns a temporary object of type _bstr_t. When this temporary goes out
of scope, it frees the underlying BSTR. The bottom line is, your code is
correct as written and does not requite explicit cleanup.
Be careful not to write something like this:
// incorrect
BSTR str = spInterface->GetString();
m_DlgItem.SetWindowText(str);
GetString returns a _bstr_t temporary. The underlying BSTR is extracted
and stored in str. At the end of the first statement, the temporary is
destroyed and str now holds a dangling pointer. If you need to store the
return value, make sure to use smart wrapper types throughout:
// correct
_bstr_t str = spInterface->GetString();
m_DlgItem.SetWindowText(str);
--
With best wishes,
Igor Tandetnik
With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925