968799 - disallow already_AddRefed members in classes

Status: NEW

(Core :: XPCOM, defect)

Description

[Nathan Froyd [:froydnj]]

The reason for doing this is that people should be making ownership more clear via .forget() and/or .swap() and/or similar.

The plan for doing this is to mark already_AddRefed as MOZ_STACK_CLASS.  This is almost airtight; the loopholes are:

- having already_AddRefed members in a MOZ_STACK_CLASS; and
- declaring already_AddRefed variables.

Ideally these will not be a problem.  (We don't seem to have any uses of either of these patterns in the tree.)  I talked this over with jcranmer and he said that MOZ_STACK_CLASS seems good enough.

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

I don't think we should do this, as I said in https://bugzilla.mozilla.org/show_bug.cgi?id=968836#c2
already_AddRefed is less hazard than nsCOMPtr when dealing with threads