1293546 - many "JavaScript error: , line 0: uncaught exception: undefined" in desktop-test-linux64/debug-mochitest-media log

Status: RESOLVED WORKSFORME

(Core :: Audio/Video: Playback, defect, P5)

Description

[Tooru Fujisawa [:arai]]

https://public-artifacts.taskcluster.net/djBUo_RRT6qwRRryXKQAQA/0/public/logs/live_backing.log
> 00:20:52     INFO -  JavaScript error: , line 0: uncaught exception: undefined
> 00:20:52     INFO -  JavaScript error: , line 0: uncaught exception: undefined

It's a promise reject, thrown from HTMLMediaElement::SetCurrentTime.
The code was changed to use promise in bug 1276272.

https://dxr.mozilla.org/mozilla-central/rev/e78975b53563d80c99ebfbdf8a9fbf6b829a8a48/dom/html/HTMLMediaElement.cpp#1656
> void
> HTMLMediaElement::SetCurrentTime(double aCurrentTime, ErrorResult& aRv)
> {
>   RefPtr<Promise> tobeDropped = Seek(aCurrentTime, SeekTarget::Accurate, aRv);
> }


that is invoked here, and also from several tests.

https://dxr.mozilla.org/mozilla-central/rev/e78975b53563d80c99ebfbdf8a9fbf6b829a8a48/dom/media/test/test_seek-4.html#30
> function startTest() {
> ...
>   v.currentTime=seekTime;
> ...
> }


HTMLMediaElement::Seek returns a promise, that can be rejected, but no one catch it.
that seems to be results in logging the uncaught exception.

https://dxr.mozilla.org/mozilla-central/rev/e78975b53563d80c99ebfbdf8a9fbf6b829a8a48/dom/html/HTMLMediaElement.cpp#1698
> already_AddRefed<Promise>
> HTMLMediaElement::Seek(double aTime,
>                        SeekTarget::Type aSeekType,
>                        ErrorResult& aRv)
> {
> ...
>     promise->MaybeRejectWithUndefined();
>     return promise.forget();

This started happening after bug 911216 push for inbound, so it could be SpiderMonkey's Promise impl's issue.
but the "tobeDropped" promise in HTMLMediaElement::SetCurrentTime is suspicious.

Comment 1

[Tzuhao Kuo [:kaku]]

(In reply to Tooru Fujisawa [:arai] from comment #0)
> This started happening after bug 911216 push for inbound, so it could be
> SpiderMonkey's Promise impl's issue.
> but the "tobeDropped" promise in HTMLMediaElement::SetCurrentTime is
> suspicious.
HTMLMediaElement::Seek() has only three callers:
(1) HTMLMediaElement::SetCurrentTime() 
    http://searchfox.org/mozilla-central/source/dom/html/HTMLMediaElement.cpp#1656
(2) HTMLMediaElement::FastSeek()
    http://searchfox.org/mozilla-central/source/dom/html/HTMLMediaElement.cpp#1644
(3) HTMLMediaElement::SeekToNextFrame()
    http://searchfox.org/mozilla-central/source/dom/html/HTMLMediaElement.cpp#1650

Only (3) needs the returned promise of HTMLMediaElement::Seek(); both (1) and (2) ignores them. How about we steal the ErrorResule in (1) and (2) before discarding the promise?

Comment 2

[Tooru Fujisawa [:arai]]

the code there is rewritten, and the error is no more reproducible.