534345 - XPCOM should refuse to hand out main-thread only components when not on the main thread

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[Peter Van der Beken [:peterv]]

Attachment: v1

Some addons try to use main-thread only components from other threads, which leads to crashes (see for example bug 521748). We should return null in that case, some addons will then crash accessing a null-pointer (again, see bug 521748), but at least it'll be a controlled crash instead of the random crashes we're currently seeing.

Comment 1

[timeless]

i've wanted this for ages.

I'm not actually certain this is the best way to go. but iirc we never got auto proxy working.

Component/Extension authors should be informed that they need to proxy their code to the main thread if they need a mainthread object.

Comment 2

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Could we just do this?

Comment 3

[Andrew McCreight [:mccr8]]

nsIClassInfo::MAIN_THREAD_ONLY is barely used nowadays so I'm not sure this is worthwhile.

Comment 4

[Andrew McCreight [:mccr8]]

Nika pointed out that nsIClassInfo is really an XPConnect concept, which is mainthread anyways, and that maybe we'd want a similar mechanism for components, but you'd want to indicate it some other way.