770172 - Assertion in unregisterIdleObserver when removing an idle observer that has never been added

Status: RESOLVED DUPLICATE of bug 770171

(Core :: DOM: Core & HTML, defect)

Description

[Vivien Nicolas (:vingtetun) (:21) - (NOT reading bugmails, needinfo? please)]

http://mxr.mozilla.org/mozilla-central/source/dom/base/nsGlobalWindow.cpp#8787

If in debug mode you call removeIdleObserver(fooObserver) but no observer add been added before, you hit an assertion.

I wonder if this is expected for an API that will be exposed to the web?

Comment 2

[bsurender]

(In reply to Vivien Nicolas (:vingtetun) from comment #0)
> http://mxr.mozilla.org/mozilla-central/source/dom/base/nsGlobalWindow.
> cpp#8787
> 
> If in debug mode you call removeIdleObserver(fooObserver) but no observer
> add been added before, you hit an assertion.
> 
> I wonder if this is expected for an API that will be exposed to the web?

If you call removeIdleObserver(fooObserver) but no idle observers have been added before then the removeIdleObserver will just print a warning andreturn NS_OK.

The assertion is because the front end dev does something with the window, after Cleanp() and/or FreeInnerObjects() have been called in nsGlobalWindow. These set the idle timer to null and then when the dev calls removeIdleObserver() it hits the idle timer null checker moz assert. This has been corrected. Patch under review.

Comment 3

[bsurender]

(In reply to bsurender from comment #2)
> (In reply to Vivien Nicolas (:vingtetun) from comment #0)
> > http://mxr.mozilla.org/mozilla-central/source/dom/base/nsGlobalWindow.
> > cpp#8787
> > 
> > If in debug mode you call removeIdleObserver(fooObserver) but no observer
> > add been added before, you hit an assertion.
> > 
> > I wonder if this is expected for an API that will be exposed to the web?
> 
> If you call removeIdleObserver(fooObserver) but no idle observers have been
> added before then the removeIdleObserver will just print a warning and return
> NS_OK.
> 
> The assertion is because the front end dev does something with the window,
> after Cleanp() and/or FreeInnerObjects() have been called in nsGlobalWindow.
> These set the idle timer to null and then when the dev calls
> removeIdleObserver() it hits the idle timer null checker moz assert. This
> has been corrected. Patch under review.

You're right. The assertion can also happen if no idle observers have been added but the idle observer but an idle observer is being removed. I have now corrected this.