396369 - Overload forget method on nsCOMPtr/nsRefPtr to work with out parameters

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Ben Turner (not reading bugmail, use the needinfo flag!)]

Attachment: Patch

This patch overloads the forget method on nsCOMPtr/nsRefPtr to work better with out parameters.

This will save a pair of addref/release calls for all methods that use the following (ubiquitous) construct:

void FooMethod(/*out*/nsIFoo** _retval)
{
  nsCOMPtr<nsIFoo> foo = ...
  NS_ADDREF(*_retval = foo);
}

New code can simply use:

  foo.forget(_retval);

Not that 'swap(_retval)' could be used but it isn't safe unless you first ensure that '*_retval' is null.

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Comment on attachment 281105 [details] [diff] [review]
Patch

There's no need for rhs to be T**&; it can just be T**.  r=dbaron with that change

Comment 2

[Ben Turner (not reading bugmail, use the needinfo flag!)]

Comment on attachment 281105 [details] [diff] [review]
Patch

Ok, will make that small change on checkin. Thanks!

Comment 3

[Benjamin Smedberg]

Comment on attachment 281105 [details] [diff] [review]
Patch

Also, you need to add this signature to the specialization of nsCOMPtr<nsISupports> below in nsCOMPtr.h

Please submit a new patch to ask for approval

Comment 4

[Ben Turner (not reading bugmail, use the needinfo flag!)]

Attachment: Updated fix

Here's the updated patch with the extra nsISupports specialization. Carrying forward r+/sr+.

Comment 5

[Damon Sicore (:damons)]

Comment on attachment 285249 [details] [diff] [review]
Updated fix

a=release drivers.

Comment 6

[Ben Turner (not reading bugmail, use the needinfo flag!)]

Fixed on trunk.