830586 - GC: JSObject::preventExtensions needs to be static

Status: RESOLVED DUPLICATE of bug 833340

(Core :: JavaScript Engine, defect)

Description

[Terrence Cole [:terrence]]

There is an accidental use of |this| that should be |self| causing the following tests to fail in a root analysis build:
    basic/testOverRecursed4.js
    jaeger/recompile/bug671943-1.js

Comment 1

[Tom S [:evilpie]]

Yeah what is the story with these anyway. Feels strange to have static and instance methods in JSObject.

Comment 2

[Terrence Cole [:terrence]]

(In reply to Tom Schuster [:evilpie] from comment #1)
> Yeah what is the story with these anyway. Feels strange to have static and
> instance methods in JSObject.

Yes it does. The problem, specifically, is |this|: it is on the stack implicitly through C++'s machinations, so we have no idea where it is. Thus, we cannot update it when we GC. So, if we do GC we have to not use |this| because the object |this| refers to could have moved. Initially we were re-rooting |this| as |self|, but given how many problems cropped up from accidentally using |this| where we shouldn't, we decided to just make most GCing methods static to prevent further regressions.

We do have some ideas to fix this. See bug 785452 in particular.