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Shu-yu Guo 9f0f2cb7f0 [weakrefs] Call Isolate::ClearKeptObjects() as part of microtask checkpoint
In the spec, WeakRefs that are dereferenced are kept alive until there's
no JS on the stack, and then the host is expected to call
ClearKeptObjects to clear those strong references [1]. HTML calls
ClearKeptObjects at the end of a PerformMicrotaskCheckpoint [2].

In V8, leaving this up to the embedder is error prone in the same way
the deprecated FinalizationGroup callback APIs were error prone: it
depends on the embedder doing the right thing. This CL moves the call to
ClearKeptObjects to be after running of microtasks within V8.

However, the Isolate::ClearKeptObjects API should not be removed or
deprecated in case an embedder uses an entirely custom MicrotaskQueue
implementation and invokes MicrotaskQueue::PerformCheckpoint manually.

[1] https://tc39.es/proposal-weakrefs/#sec-clear-kept-objects
[2] https://github.com/whatwg/html/pull/4571

Bug: v8:8179
Change-Id: Ie243804157b56241ca69ed8fad300e839a0c9f75
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2055967
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66327}
2020-02-19 02:25:34 +00:00
build_overrides Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
custom_deps Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
docs Add OWNERS for docs/ 2019-05-15 12:06:15 +00:00
gni [tools] Add v8windbg, a WinDbg extension for V8 2020-02-18 19:16:18 +00:00
include [weakrefs] Call Isolate::ClearKeptObjects() as part of microtask checkpoint 2020-02-19 02:25:34 +00:00
infra Test with --no-lazy-feedback-allocation on one x64 builder set. 2020-02-17 16:10:37 +00:00
samples [cleanup] Drop some occurrences of Isolate::Current 2019-06-26 19:39:21 +00:00
src [weakrefs] Call Isolate::ClearKeptObjects() as part of microtask checkpoint 2020-02-19 02:25:34 +00:00
test [weakrefs] Call Isolate::ClearKeptObjects() as part of microtask checkpoint 2020-02-19 02:25:34 +00:00
testing Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
third_party [DevTools] Roll inspector_protocol (v8) 2020-02-11 18:45:53 +00:00
tools [tools] Add v8windbg, a WinDbg extension for V8 2020-02-18 19:16:18 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.clang-tidy [tool] Remove unfixed clang-tidy warnings to ease use. 2018-10-26 07:40:32 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.flake8 Add .flake8 to allow for python style checking. 2019-07-19 21:44:03 +00:00
.git-blame-ignore-revs Add recent code rewrite to .git-blame-ignore-revs 2019-05-23 10:38:45 +00:00
.gitattributes .gitattributes: Mark minified emscripten js files as -diff 2018-09-19 16:27:10 +00:00
.gitignore [git] Ignore jit-*.dump files 2020-01-07 12:14:15 +00:00
.gn [build] Dynamically decide if to use system xcode 2019-07-29 08:20:24 +00:00
.vpython [tools] Implement confidence-based number of runs 2019-05-09 09:42:28 +00:00
.ycm_extra_conf.py Fix ycm config for headers without source 2019-12-09 11:59:21 +00:00
AUTHORS [build] Add new build argument v8_symbol_level 2020-02-13 17:48:48 +00:00
BUILD.gn Revert "[turbofan] Fast API calls from TurboFan" 2020-02-18 20:49:58 +00:00
CODE_OF_CONDUCT.md Explicitly state that the Chromium Code of Conduct also applies to V8 2016-03-02 09:51:24 +00:00
codereview.settings Make Gerrit the default code review for V8 2017-06-30 17:37:37 +00:00
COMMON_OWNERS [OWNERS] Add dinfuehr@ to COMMON_OWNERS 2020-01-10 14:42:32 +00:00
DEPS Update V8 DEPS. 2020-02-17 03:53:19 +00:00
ENG_REVIEW_OWNERS Add eng review owners as escalation path 2019-05-15 19:12:10 +00:00
INFRA_OWNERS Remove myself from owners 2019-12-12 14:22:32 +00:00
INTL_OWNERS Add missing owners files 2019-05-31 07:21:01 +00:00
LICENSE [wasm] Draft version of C/C++ Wasm API 2019-04-17 16:00:26 +00:00
LICENSE.fdlibm Add LICENSE.fdlibm for all the fdlibm imported sources. 2016-06-09 07:17:03 +00:00
LICENSE.strongtalk Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.v8 Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.valgrind Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
MIPS_OWNERS Move architecture dependent files 2019-05-28 14:02:15 +00:00
OWNERS Add syg@chromium.org as DEPS owner for test262 rolls 2019-09-17 19:29:11 +00:00
PPC_OWNERS Move architecture dependent files 2019-05-28 14:02:15 +00:00
PRESUBMIT.py Remove the #undef check from the Presubmit for .cc files 2020-01-24 15:24:51 +00:00
README.md [docs] Change links from old wiki to v8.dev 2019-03-07 12:13:30 +00:00
S390_OWNERS Move architecture dependent files 2019-05-28 14:02:15 +00:00
WATCHLISTS Remove myself from WATCHLISTS 2020-01-18 00:34:32 +00:00

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://v8.dev/docs

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 at v8.dev/docs/contribute.