src: add internal binding for constructing SharedArrayBuffers

[Renegade334]

SharedArrayBuffers are finding more and more use in core, but the flag-dependent exposure of the constructor is a permanent issue. In the common case where the constructor is available, the global is potentially user-mutable depending on when it's accessed, and in the case where the constructor isn't available, this either results in deliberately lost functionality or just straight runtime errors.

The approach here adds a utility binding to construct SABs via the V8 API, which is ubiquitously available independent of the flag state.

An alternative approach would be to use the JS global if present, and only call into C++ if absent. In reality, this method is vanishingly unlikely to ever be needed in a hot path, so the call cost isn't as much of a consideration, and using the API adds the primordial-esque safety factor.

Would supersede #60453. Does not land on v20.x or v22.x, as MaybeNew was added in V8 13.1.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders
• @nodejs/streams

[codecov]

Codecov Report

❌ Patch coverage is 90.74074% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.54%. Comparing base (f46152f) to head (3651c31).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_util.cc	73.68%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60497      +/-   ##
==========================================
- Coverage   88.58%   88.54%   -0.05%     
==========================================
  Files         704      704              
  Lines      207839   207854      +15     
  Branches    40051    40039      -12     
==========================================
- Hits       184117   184039      -78     
- Misses      15791    15849      +58     
- Partials     7931     7966      +35     

Files with missing lines	Coverage Δ
lib/internal/main/worker_thread.js	94.35% <100.00%> (-0.10%)	⬇️
lib/internal/modules/esm/hooks.js	86.17% <100.00%> (-0.07%)	⬇️
lib/internal/streams/fast-utf8-stream.js	74.23% <100.00%> (+0.02%)	⬆️
lib/internal/util.js	96.37% <100.00%> (+<0.01%)	⬆️
lib/internal/worker.js	96.52% <100.00%> (+<0.01%)	⬆️
lib/internal/worker/messaging.js	100.00% <100.00%> (ø)
src/node_util.cc	80.00% <73.68%> (-1.00%)	⬇️

... and 39 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/69961/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/69964/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/69967/

[nodejs-github-bot]

Commit Queue failed

- Loading data for nodejs/node/pull/60497
✔  Done loading data for nodejs/node/pull/60497
----------------------------------- PR info ------------------------------------
Title      src: add internal binding for constructing SharedArrayBuffers (#60497)
Author     René <contact.9a5d6388@renegade334.me.uk> (@Renegade334)
Branch     Renegade334:bound-sharedarraybuffer-construct -> nodejs:main
Labels     lib / src, author ready, needs-ci, commit-queue-rebase, dont-land-on-v20.x, dont-land-on-v22.x
Commits    2
 - src: add internal binding for constructing SharedArrayBuffers
 - lib: replace global SharedArrayBuffer constructor with bound method
Committers 1
 - Renegade334 <contact.9a5d6388@renegade334.me.uk>
PR-URL: https://github.com/nodejs/node/pull/60497
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Shelley Vohr <shelley.vohr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/60497
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Shelley Vohr <shelley.vohr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Thu, 30 Oct 2025 16:37:41 GMT
   ✔  Approvals: 3
   ✔  - Antoine du Hamel (@aduh95) (TSC): https://github.com/nodejs/node/pull/60497#pullrequestreview-3400899628
   ✔  - Shelley Vohr (@codebytere): https://github.com/nodejs/node/pull/60497#pullrequestreview-3403743107
   ✔  - Colin Ihrig (@cjihrig): https://github.com/nodejs/node/pull/60497#pullrequestreview-3404542988
   ⚠  This PR has conflicts that must be resolved
   ✔  Last GitHub CI successful
   ℹ  Last Full PR CI on 2025-10-31T11:35:25Z: https://ci.nodejs.org/job/node-test-pull-request/69967/
- Querying data for job/node-test-pull-request/69967/
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   ✔  Aborted `git node land` session in /home/runner/work/node/node/.ncu

https://github.com/nodejs/node/actions/runs/18999682275

[Renegade334]

Rebased for merge conflict.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/69995/