[js weak ref] Make JSWeakRef / WeakCell target handling more robust

1) JSWeakRef and WeakCell targets are HeapObjects (SMIs are no longer used for
signalling cleared / dead JSWeakRefs / WeakCells.) Make this explicit.

2) There's no need to assert that the target of JSWeakRef cannot be undefined
when handled by MarkCompactCollector::ClearJSWeakRefs, since the code handles
undefined just fine. (The removed comment was true though, since this is the only place
which can set the target to undefined. But maybe in the future there's some
other way to clear a JSWeakRef, e.g., explicit API for it.)

BUG=v8:8179

Change-Id: I762c2b4487770712c7538be799dc188943c92587
Reviewed-on: https://chromium-review.googlesource.com/c/1445986
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59237}
5 files changed
tree: 01cf3dccbf269da184c5639362ba74cdd70c794f
  1. .clang-format
  2. .clang-tidy
  3. .editorconfig
  4. .git-blame-ignore-revs
  5. .gitattributes
  6. .gitignore
  7. .gn
  8. .vpython
  9. .ycm_extra_conf.py
  10. AUTHORS
  11. BUILD.gn
  12. CODE_OF_CONDUCT.md
  13. ChangeLog
  14. DEPS
  15. LICENSE
  16. LICENSE.fdlibm
  17. LICENSE.strongtalk
  18. LICENSE.v8
  19. LICENSE.valgrind
  20. OWNERS
  21. PRESUBMIT.py
  22. README.md
  23. WATCHLISTS
  24. benchmarks/
  25. build_overrides/
  26. codereview.settings
  27. custom_deps/
  28. docs/
  29. gni/
  30. include/
  31. infra/
  32. samples/
  33. snapshot_toolchain.gni
  34. src/
  35. test/
  36. testing/
  37. third_party/
  38. tools/
README.md

V8 JavaScript Engine

V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page: https://github.com/v8/v8/wiki

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*

Contributing

Please follow the instructions mentioned on the V8 wiki.