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Anton Bikineev 3984ddc0a9 cppgc: young-gen: Always execute custom weak callbacks for old objects
Custom callbacks assume that untraced pointers always point to valid,
not freed objects. They must make sure that upon callback completion no
UntracedMembers point to an unreachable object. This may not hold true
if a custom callback for an old object operates with a reference to a
young object that was freed on a minor collection cycle. To maintain
the mentioned invariant, the CL calls custom callbacks for old objects
on every minor collection cycle.

The alternative options could be:
1) Replacing all UntracedMembers with WeakMembers, since WeakMember
   supports tracing and the barrier.
2) Emitting the generational barrier for UntracedMember + tracing
   UntracedMember on minor collection cycles.
The first option requires changing multiple use sites and can bring some
performance regression. The second option requires changing the GC logic
and the semantics of UntracedMember.

Bug: chromium:1029379
Change-Id: I9bb89e4787daf05990feed374dceca940be7be63
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3472499
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79221}
2022-02-23 09:52:56 +00:00
.github [github] Close PRs created on the V8 GitHub mirror automatically 2021-01-12 08:39:59 +00:00
bazel [bazel] Improve bazel build 2022-02-16 11:40:13 +00:00
build_overrides [build] Remove obsolete gn flag 2021-01-11 15:50:59 +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 [cleanup] Remove deprecated build flag v8_enable_raw_heap_snapshots 2022-02-18 16:21:20 +00:00
include [sandbox] Store external pointers in EmbedderDataSlots in shifted form 2022-02-22 13:40:35 +00:00
infra [infra] migrate simple PRESUBMIT scripts to py3 2022-02-18 13:43:30 +00:00
samples Initialize V8 sandbox in samples 2022-02-14 11:15:10 +00:00
src cppgc: young-gen: Always execute custom weak callbacks for old objects 2022-02-23 09:52:56 +00:00
test cppgc: young-gen: Always execute custom weak callbacks for old objects 2022-02-23 09:52:56 +00:00
testing [test][cleanup] Fix -Wshadow warnings in unittests 2021-09-27 08:59:01 +00:00
third_party Update V8 DEPS. 2022-01-26 12:51:01 +00:00
tools Reland "[shared-struct] Prototype JS shared structs" 2022-02-23 01:37:55 +00:00
.bazelrc [bazel] Use v8_enable_handle_zapping only in debug builds. 2022-01-11 11:32:39 +00:00
.clang-format
.clang-tidy [tool] Remove unfixed clang-tidy warnings to ease use. 2018-10-26 07:40:32 +00:00
.editorconfig
.flake8 remove swarming_client 2021-08-24 10:39:33 +00:00
.git-blame-ignore-revs [infra] Update .git-blame-ignore-revs 2020-03-03 12:59:13 +00:00
.gitattributes .gitattributes: Mark minified emscripten js files as -diff 2018-09-19 16:27:10 +00:00
.gitignore remove swarming_client 2021-08-24 10:39:33 +00:00
.gn Revert "[build] Separate out inspector as a shared library" 2021-07-02 16:15:20 +00:00
.mailmap Restore consistency between .mailmap and AUTHORS 2021-06-24 08:58:04 +00:00
.style.yapf [tools] Add basic pointer compression to grokdump 2022-02-04 14:35:26 +00:00
.vpython Verify mac-arm64 wheels for v8/.vpython spec. 2021-09-15 21:11:50 +00:00
.vpython3 [infra] Make various scripts compatible with Python3 2022-02-04 07:17:24 +00:00
.ycm_extra_conf.py [ycm] Fix python script 2021-07-29 09:48:32 +00:00
AUTHORS [riscv64] Add RVV Float-Point Widening Instructions 2022-02-22 10:59:25 +00:00
BUILD.bazel Reland "[shared-struct] Prototype JS shared structs" 2022-02-23 01:37:55 +00:00
BUILD.gn Reland "[shared-struct] Prototype JS shared structs" 2022-02-23 01:37:55 +00:00
CODE_OF_CONDUCT.md
codereview.settings
COMMON_OWNERS Update OWNERS files 2022-02-16 08:16:04 +00:00
DEPS Update V8 DEPS. 2022-02-23 04:09:15 +00:00
DIR_METADATA Add DIR_METADATA files to v8. 2020-10-20 22:12:28 +00:00
ENG_REVIEW_OWNERS Add verwaest@ to ENG_REVIEW_OWNERS. 2021-09-16 15:00:57 +00:00
INFRA_OWNERS Add team members as owners 2020-08-18 08:29:04 +00:00
INTL_OWNERS add ftang as owner 2020-04-24 19:19:36 +00:00
LICENSE [wasm] Draft version of C/C++ Wasm API 2019-04-17 16:00:26 +00:00
LICENSE.fdlibm
LICENSE.strongtalk
LICENSE.v8
LOONG_OWNERS [LOONG64] Add LoongArch64 backend 2021-08-16 13:05:19 +00:00
MIPS_OWNERS [mips] Add LiuYu to MIPS_OWNERS 2021-09-08 01:38:52 +00:00
OWNERS Let infra owners own all dot files 2021-11-05 18:57:18 +00:00
PPC_OWNERS Adding myself to relevant OWNERS files. 2020-11-02 16:37:28 +00:00
PRESUBMIT.py [infra] migrate the main PRESUBMIT script to py3 2022-02-18 13:44:33 +00:00
README.md [docs] Change links from old wiki to v8.dev 2019-03-07 12:13:30 +00:00
RISCV_OWNERS Add Lu Yahan to RISC-V owners list 2021-09-13 16:35:00 +00:00
S390_OWNERS Adding myself to relevant OWNERS files. 2020-11-02 16:37:28 +00:00
WATCHLISTS Add myself to heap/ watchlist 2021-11-08 16:58:14 +00:00
WORKSPACE [bazel] Cleanup style with Buildifier. 2022-01-11 10:00:36 +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.