GitLab

Weak containers are marked by the MarkingVisitor when reached through
regular tracing. However, weak containers might not be traced (e.g. in
case of a weak-to-weak HashMap). Ephemerons are traced, but only values
belonging to live keys are marked. At the end of marking, all unmarked
buckets in the container are removed.

If the container is reachable from stack (e.g. via an iterator), all
buckets become reachable, meaning all buckets should be marked as live.
However, conservative GC does not re-trace a previously marked/traced
container, resulting in dangling references (to deleted buckets) and
invalid iterators.

This CL marks all marked weak containers so that conservative GC knows
to retrace them if they are found again through stack scanning.

Bug: 1108676
Change-Id: I8790c4af2dcd70513b77c4a5fced4ce85852a9c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2489905
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819493}