1755725 - WeakRefs don't work with cross-zone targets

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect, P3)

Description

[Jon Coppeard (:jonco)]

When investigating optimising the way we implement the kept objects set used by WeakRefs, I noticed they didn't work at all when their target is in another zone. Doing this results in the WeakRef returning undfined from the deref() method after GC, even if the target is still alive.

I don't know how often these are used with cross-zone targets or how to arrange this in the browser but I assume it's possible.

Comment 1

[Jon Coppeard (:jonco)]

Attachment: Bug 1755725 - Part 1: Factor out crossZoneWrappers checks and do them before we calculate sweep groups r?sfink

Comment 2

[Jon Coppeard (:jonco)]

Attachment: Bug 1755725 - Part 2: Refactor FinalizationObservers in preparation to add a weak set for weak refs r?sfink

This renames crossZoneWarppers to crossZoneRecordWrappers and makes
add/RemoveCrossZoneWarpper take the set as an argument.

Depends on D139835

Comment 3

[Jon Coppeard (:jonco)]

Attachment: Bug 1755725 - Part 3: Add cross-zone WeakRef wrappers to a weak set to keep them alive r?sfink

This fixes weak ref behaviour with cross zone targets. Previously the wrapper
died because there was nothing to keep it alive and the weak ref target was
cleared, even if the target was still alive.

Depends on D139836

Comment 4

[Jon Coppeard (:jonco)]

Attachment: Bug 1755725 - Part 4: Add WeakRef tests where the weak ref and its target are in different zones r?sfink

Depends on D139837

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/59ae32a4a0a3
Part 1: Factor out crossZoneWrappers checks and do them before we calculate sweep groups r=sfink
https://hg.mozilla.org/integration/autoland/rev/8e7816b5ea2a
Part 2: Refactor FinalizationObservers in preparation to add a weak set for weak refs r=sfink
https://hg.mozilla.org/integration/autoland/rev/eac621ee0ea8
Part 3: Add cross-zone WeakRef wrappers to a weak set to keep them alive r=sfink
https://hg.mozilla.org/integration/autoland/rev/2f4c3dcd4a8d
Part 4: Add WeakRef tests where the weak ref and its target are in different zones r=sfink

Comment 6

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/59ae32a4a0a3
https://hg.mozilla.org/mozilla-central/rev/8e7816b5ea2a
https://hg.mozilla.org/mozilla-central/rev/eac621ee0ea8
https://hg.mozilla.org/mozilla-central/rev/2f4c3dcd4a8d