Hi folks,
I'm still a bit confused on which types (nsCOMPtr, ...) to use when
exactly, in combination w/ IDLs.
Let's consider a case where an nsArray is created and returned
(as rval, not out-parameter):
IDL:
[scriptable, uuid(ea0d8b3d-a549-4666-82d8-3a82cee2a3f1)]
interface nsIAddrBookService : nsISupports
{
nsIArray FindRecipients(in AString name);
...
}
C++:
/* nsIArray FindRecipients (in AString name); */
NS_IMETHODIMP nsAddrBookService::FindRecipients(const nsAString & addr,
nsIArray * *_retval)
{
nsresult rv = NS_OK;
nsCOMPtr<nsIMutableArray> list =
do_CreateInstance(NS_ARRAY_CONTRACTID, &rv);
NS_ENSURE_SUCCESS(rv, rv);
*_retval = list;
return FillRecipients(addr, list);
}
I'd assume that do_CreateInstance() returns the object w/ refcnt=1.
The assignment to nsCOMPtr should increase refcount. Correct ?
When the function is left, the nsCOMPtr is destroyed, and refcnt
goes back to 1 (we now have a reference left in the caller's pointer
field).
Now the caller side: (inspired by various examples ...)
nsCOMPtr<nsIArray> list;
rv = addrBookService->FindRecipients(
splittedRecipients[j].mEmail,
getter_AddRefs(list));
I'd guess getter_AddRefs() causes refcnt to be increased again, so
we're back at 2. That could lead to a leak, when that function returns
(and doesn't pass the ref anywhere else).
So, should I use dont_AddRef() here ?
Is the situation different when using out parameter instead of rval ?
BTW: what happens when passing nsCOMPtr as a reference (w/o IDL) ?
Assume the following code:
void caller() {
nsCOMPtr<nsIFoo> ref;
callee(ref);
ref->Something();
}
void callee(nsCOMPtr & outref) {
nsCOMPtr<nsIFoo> myref = do_CreateInstance(...);
...
outref = myref;
}
I'd assume that the last line will fill the caller's ref field w/ the
pointer and increase the object's refcnt (so it's 2 now), then when
callee is left, its myref is destroyed and refcnt is back to 1.
Is that correct ?
--mtx
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