1179374 - add addRefIntoOutparam(T**)/copyAndAddRef methods to smart pointer classes

Status: NEW

(Core :: XPCOM, defect)

Description

[Nathan Froyd [:froydnj]]

Looking at some of the patterns of NS_ADDREF we have in the tree, one reasonably common one is:

  nsRefPtr<Class> mFoo;
  ...

  NS_ADDREF(*aOutFoo = mFoo);
  return NS_OK;

I think changing this, in the spirit of .forget(T**), to:

  mFoo.addRefIntoOutparam(aOutFoo);
  return NS_OK;

would be an improvement.

Equally, as we move away from XPCOM outparam semantics, one sometimes sees (this is particularly common in gfx code):

  nsRefPtr<Class> mFoo;

  already_AddRefed<Class>
  Outer::Method(...)
  {
     nsRefPtr<Class> copy(mFoo);
     return copy.forget();
  }

we should have a helper method to just say:

  return mFoo.copyAndAddRef();

(This is admittedly kind of a hack to workaround our non-use of move semantics for smart pointer return values.)

Bikeshedding on the names welcome.