src: fix timing of snapshot serialize callback #60434

joyeecheung · 2025-10-27T14:31:11Z

src: add COUNT_GENERIC_USAGE utility for tests

src: fix timing of snapshot serialize callback

Previously the addAfterUserSerailizeCallback() wasn't
ready to be used for building the built-in snapshot.
This patch initializes the callbacks at the time
lib/internal/v8/start_snapshot.js is loaded, so that
these callbacks get run correctly when building the
built-in snapshot.

Currently when building the built-in snapshot,
addAfterUserSerializeCallback() is only used by createUnsafeBuffer(),
other usages can only come from user-land snapshots,
which is covered by tests, but what gets run by the
built-in snapshot building process is less visible, and the
path used by createUnsafeBuffer() isn't reliably visible in user
land either. This adds an internal usage counter in debug builds
to verify this path when building the built-in snapshot.

Fixes: #60423

Previously the addAfterUserSerailizeCallback() wasn't ready to be used for building the built-in snapshot. This patch initializes the callbacks at the time lib/internal/v8/start_snapshot.js is loaded, so that these callbacks get run correctly when building the built-in snapshot. Currently when building the built-in snapshot, addAfterUserSerializeCallback() is only used by createUnsafeBuffer(), other usages can only come from user-land snapshots, which is covered by tests, but what gets run by the built-in snapshot building process is less visible, and the path used by createUnsafeBuffer() isn't reliably visible in user land either. This adds an internal usage counter in debug builds to verify this path when building the built-in snapshot.

ChALkeR

Note: this effectively disables --zero-fill-buffers default being on since 24.0.0
If not for a significant perf impact, this should have been a semver-major change at this point

codecov · 2025-10-27T15:36:07Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.57%. Comparing base (3c8c1ef) to head (d6d4659).
⚠️ Report is 21 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60434      +/-   ##
==========================================
+ Coverage   88.07%   88.57%   +0.50%     
==========================================
  Files         704      704              
  Lines      207778   207814      +36     
  Branches    39949    40038      +89     
==========================================
+ Hits       182998   184078    +1080     
+ Misses      16791    15775    -1016     
+ Partials     7989     7961      -28

Files with missing lines	Coverage Δ
lib/internal/main/mksnapshot.js	`95.87% <ø> (-0.04%)`	⬇️
lib/internal/v8/startup_snapshot.js	`95.38% <100.00%> (+9.23%)`	⬆️
src/api/environment.cc	`76.88% <100.00%> (-0.14%)`	⬇️

... and 103 files with indirect coverage changes

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mcollina

RSLGTM

nodejs-github-bot · 2025-10-27T16:12:16Z

CI: https://ci.nodejs.org/job/node-test-pull-request/69905/

test/parallel/test-buffer-alloc-unsafe-is-uninitialized.js

ChALkeR · 2025-10-27T16:18:45Z

Also this likely should be both a notable change and have a clear description that it disables default buffer zero-filling, which has been accidental

test/parallel/test-buffer-alloc-unsafe-is-uninitialized.js

aduh95

Testing ./node -e 'for (let i = 0; i < 1e6; i++) {if(Buffer.allocUnsafe(4096).some(x=>x))process.exit(0)}process.exit(1)' is failing without this patch, and passing with it

nodejs-github-bot · 2025-10-27T17:18:02Z

CI: https://ci.nodejs.org/job/node-test-pull-request/69907/

github-actions · 2025-10-27T17:20:29Z

Fast-track has been requested by @aduh95. Please 👍 to approve.

aduh95 · 2025-10-27T17:20:45Z

Fast track so it can get into #60436?

nodejs-github-bot · 2025-10-27T22:09:50Z

CI: https://ci.nodejs.org/job/node-test-pull-request/69909/

aduh95 · 2025-10-28T00:10:29Z

Adding baking-for-lts PRs that need to wait before landing in a LTS release. as I don't think there's consensus regarding whether this should land on v24.x.

nodejs-github-bot · 2025-10-28T00:12:04Z

Commit Queue failed

- Loading data for nodejs/node/pull/60434 ✔ Done loading data for nodejs/node/pull/60434 ----------------------------------- PR info ------------------------------------ Title src: fix timing of snapshot serialize callback (#60434) Author Joyee Cheung <[email protected]> (@joyeecheung) Branch joyeecheung:buffer -> nodejs:main Labels c++, lib / src, baking-for-lts, fast-track, author ready, needs-ci Commits 4 - src: add COUNT_GENERIC_USAGE utility for tests - src: fix timing of snapshot serialize callback - fixup! src: fix timing of snapshot serialize callback - fixup! fixup! src: fix timing of snapshot serialize callback Committers 1 - Joyee Cheung <[email protected]> PR-URL: https://github.com/nodejs/node/pull/60434 Fixes: https://github.com/nodejs/node/issues/60423 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Richard Lau <[email protected]> ------------------------------ Generated metadata ------------------------------ PR-URL: https://github.com/nodejs/node/pull/60434 Fixes: https://github.com/nodejs/node/issues/60423 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Richard Lau <[email protected]> -------------------------------------------------------------------------------- ℹ This PR was created on Mon, 27 Oct 2025 14:31:11 GMT ✔ Approvals: 3 ✔ - Matteo Collina (@mcollina) (TSC): https://github.com/nodejs/node/pull/60434#pullrequestreview-3384325240 ✔ - Antoine du Hamel (@aduh95) (TSC): https://github.com/nodejs/node/pull/60434#pullrequestreview-3384634586 ✔ - Richard Lau (@richardlau) (TSC): https://github.com/nodejs/node/pull/60434#pullrequestreview-3386023877 ℹ This PR is being fast-tracked ✔ Last GitHub CI successful ℹ Last Full PR CI on 2025-10-27T22:09:50Z: https://ci.nodejs.org/job/node-test-pull-request/69909/ - Querying data for job/node-test-pull-request/69909/ ✔ Last Jenkins CI successful -------------------------------------------------------------------------------- ✔ No git cherry-pick in progress ✔ No git am in progress ✔ No git rebase in progress -------------------------------------------------------------------------------- - Bringing origin/main up to date... From https://github.com/nodejs/node * branch main -> FETCH_HEAD ✔ origin/main is now up-to-date - Downloading patch for 60434 From https://github.com/nodejs/node * branch refs/pull/60434/merge -> FETCH_HEAD ✔ Fetched commits as 51a57f2b3629..d6d46594f8e8 -------------------------------------------------------------------------------- [main 74f6c4aa82] src: add COUNT_GENERIC_USAGE utility for tests Author: Joyee Cheung <[email protected]> Date: Mon Oct 27 13:42:30 2025 +0100 3 files changed, 35 insertions(+), 2 deletions(-) [main 7f70321948] src: fix timing of snapshot serialize callback Author: Joyee Cheung <[email protected]> Date: Mon Oct 27 13:43:09 2025 +0100 3 files changed, 18 insertions(+), 3 deletions(-) create mode 100644 test/parallel/test-buffer-alloc-unsafe-is-uninitialized.js [main 9f399a1b9a] fixup! src: fix timing of snapshot serialize callback Author: Joyee Cheung <[email protected]> Date: Mon Oct 27 17:42:51 2025 +0100 2 files changed, 21 insertions(+) create mode 100644 test/parallel/test-buffer-alloc-unsafe-is-initialized-with-zero-fill-flag.js [main d7be4afbbf] fixup! fixup! src: fix timing of snapshot serialize callback Author: Joyee Cheung <[email protected]> Date: Mon Oct 27 18:11:18 2025 +0100 2 files changed, 14 insertions(+), 8 deletions(-) ✔ Patches applied There are 4 commits in the PR. Attempting autorebase. Rebasing (2/6) Executing: git node land --amend --yes --------------------------------- New Message ---------------------------------- src: add COUNT_GENERIC_USAGE utility for tests

PR-URL: #60434
Fixes: #60423
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Richard Lau <[email protected]>

[detached HEAD 9fdcd00dfb] src: add COUNT_GENERIC_USAGE utility for tests
Author: Joyee Cheung <[email protected]>
Date: Mon Oct 27 13:42:30 2025 +0100
3 files changed, 35 insertions(+), 2 deletions(-)
Rebasing (3/6)
Rebasing (4/6)
Rebasing (5/6)
Rebasing (6/6)
Executing: git node land --amend --yes
--------------------------------- New Message ----------------------------------
src: fix timing of snapshot serialize callback

Previously the addAfterUserSerailizeCallback() wasn't
ready to be used for building the built-in snapshot.
This patch initializes the callbacks at the time
lib/internal/v8/start_snapshot.js is loaded, so that
these callbacks get run correctly when building the
built-in snapshot.

Currently when building the built-in snapshot,
addAfterUserSerializeCallback() is only used by createUnsafeBuffer(),
other usages can only come from user-land snapshots,
which is covered by tests, but what gets run by the
built-in snapshot building process is less visible, and the
path used by createUnsafeBuffer() isn't reliably visible in user
land either. This adds an internal usage counter in debug builds
to verify this path when building the built-in snapshot.

PR-URL: #60434
Fixes: #60423
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Richard Lau <[email protected]>

[detached HEAD d0d715d66a] src: fix timing of snapshot serialize callback
Author: Joyee Cheung <[email protected]>
Date: Mon Oct 27 13:43:09 2025 +0100
4 files changed, 45 insertions(+), 3 deletions(-)
create mode 100644 test/parallel/test-buffer-alloc-unsafe-is-initialized-with-zero-fill-flag.js
create mode 100644 test/parallel/test-buffer-alloc-unsafe-is-uninitialized.js
Successfully rebased and updated refs/heads/main.

ℹ Add commit-queue-squash label to land the PR as one commit, or commit-queue-rebase to land as separate commits.

https://github.com/nodejs/node/actions/runs/18859727179

addaleax · 2025-10-28T00:13:49Z

src/node_debug.cc

 using v8::Value;

+thread_local std::unordered_map<std::string, int> generic_usage_counters;
 thread_local std::unordered_map<FastStringKey, int, FastStringKey::Hash>


Let's make this use FastStringKey as well, that is useful here for the same reason as it is for fast API call count tracking

addaleax · 2025-10-28T00:14:46Z

src/node_debug.cc

+  if (generic_usage_counters.find(counter_name) == generic_usage_counters.end())
+    generic_usage_counters[counter_name] = 0;


Suggested change

if (generic_usage_counters.find(counter_name) == generic_usage_counters.end())

generic_usage_counters[counter_name] = 0;

... since this doesn't actually do anything, right? operator[] creates the element for you if it doesn't exist

will do a separate PR – #60447

nodejs-github-bot · 2025-10-28T00:15:57Z

Landed in 51a57f2...1f6b681

PR-URL: #60434 Fixes: #60423 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Richard Lau <[email protected]>

Previously the addAfterUserSerailizeCallback() wasn't ready to be used for building the built-in snapshot. This patch initializes the callbacks at the time lib/internal/v8/start_snapshot.js is loaded, so that these callbacks get run correctly when building the built-in snapshot. Currently when building the built-in snapshot, addAfterUserSerializeCallback() is only used by createUnsafeBuffer(), other usages can only come from user-land snapshots, which is covered by tests, but what gets run by the built-in snapshot building process is less visible, and the path used by createUnsafeBuffer() isn't reliably visible in user land either. This adds an internal usage counter in debug builds to verify this path when building the built-in snapshot. PR-URL: #60434 Fixes: #60423 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Richard Lau <[email protected]>

PR-URL: #60434 Fixes: #60423 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Richard Lau <[email protected]>

Previously the addAfterUserSerailizeCallback() wasn't ready to be used for building the built-in snapshot. This patch initializes the callbacks at the time lib/internal/v8/start_snapshot.js is loaded, so that these callbacks get run correctly when building the built-in snapshot. Currently when building the built-in snapshot, addAfterUserSerializeCallback() is only used by createUnsafeBuffer(), other usages can only come from user-land snapshots, which is covered by tests, but what gets run by the built-in snapshot building process is less visible, and the path used by createUnsafeBuffer() isn't reliably visible in user land either. This adds an internal usage counter in debug builds to verify this path when building the built-in snapshot. PR-URL: #60434 Fixes: #60423 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Richard Lau <[email protected]>

This addresses late review comments for the recently landed cfbfc1b. Refs: nodejs#60434 (review)

This addresses late review comments for the recently landed cfbfc1b and aligns the new code with the pre-existing V8 fast call counters. Refs: nodejs#60434 (review)

ChALkeR · 2025-10-28T00:38:05Z

Given this landed, how fast can it get into 24?

panva · 2025-10-28T20:06:39Z

Adding baking-for-lts PRs that need to wait before landing in a LTS release. as I don't think there's consensus regarding whether this should land on v24.x.

Why should restoring documented behaviour that's present on 22 and now 25 need wait to land on 24? I think baking-for-lts PRs that need to wait before landing in a LTS release. should be dropped here.

panva · 2025-10-28T20:26:09Z

I'm removing baking-for-lts PRs that need to wait before landing in a LTS release. since the intent to restore the documented behaviour is already part of the blog post and will be updated in the release notes too.

src: add COUNT_GENERIC_USAGE utility for tests

0f2ecc3

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels Oct 27, 2025

joyeecheung mentioned this pull request Oct 27, 2025

allocUnsafe is useless since 24 #60423

Open

joyeecheung force-pushed the buffer branch from fdada92 to 454caf1 Compare October 27, 2025 14:39

joyeecheung mentioned this pull request Oct 27, 2025

src: migrate from deprecated SnapshotCreator constructor #55337

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ChALkeR reviewed Oct 27, 2025

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test/parallel/test-buffer-alloc-unsafe-is-uninitialized.js Show resolved Hide resolved

fixup! src: fix timing of snapshot serialize callback

998b033

joyeecheung force-pushed the buffer branch from db5ebff to 998b033 Compare October 27, 2025 16:46

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fixup! fixup! src: fix timing of snapshot serialize callback

d6d4659

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2025-10-28, Version 25.1.0 (Current) #60436

Merged

addaleax added a commit to addaleax/node that referenced this pull request Oct 28, 2025

src: clean up generic counter implementation

63f9230

This addresses late review comments for the recently landed cfbfc1b. Refs: nodejs#60434 (review)

addaleax mentioned this pull request Oct 28, 2025

src: clean up generic counter implementation #60447

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panva added lts-watch-v24.x PRs that may need to be released in v24.x and removed baking-for-lts PRs that need to wait before landing in a LTS release. labels Oct 28, 2025

		if (generic_usage_counters.find(counter_name) == generic_usage_counters.end())
		generic_usage_counters[counter_name] = 0;

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src: fix timing of snapshot serialize callback #60434

src: fix timing of snapshot serialize callback #60434

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src: add COUNT_GENERIC_USAGE utility for tests