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Fix crash in FinalizationRegistry when the observed object is GC'd #371

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Merged
merged 1 commit into from
Apr 12, 2024

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saghul
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@saghul saghul commented Apr 11, 2024

In the pathological case shown in
#367 both the object and the registry will be destroyed as part of the GC phase of JS_FreeRuntime. When the GC sweep happens it's possible we are holding on to a corpse so avoid calling the registry callback in that case.

This is similar to how Weak{Map,Set} deal with iterators being freed as part of a cycle.

Fixes: #367

In the pathological case shown in
#367 both the object and the
registry will be destroyed as part of the GC phase of JS_FreeRuntime.
When the GC sweep happens it's possible we are holding on to a corpse so
avoid calling the registry callback in that case.

This is similar to how Weak{Map,Set} deal with iterators being freed as
part of a cycle.

Fixes: #367
@saghul saghul requested a review from bnoordhuis April 11, 2024 20:44
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LGTM, I think, but a question: doesn't held_value turn into JS_UNDEFINED when it's collected?

JS_IsLiveObject is functionally equivalent to JS_IsUndefined if that's the case, I'm just wondering if that's indeed how it works.

@saghul
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saghul commented Apr 12, 2024

LGTM, I think, but a question: doesn't held_value turn into JS_UNDEFINED when it's collected?

Not quite. It's still an object, but it has no shape and in the next phase it will be freed.

@saghul saghul merged commit 38fa7d7 into master Apr 12, 2024
@saghul saghul deleted the fix-finrec branch April 12, 2024 10:23
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"FinalizationRegistry" bug
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