René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"AbortSignal.any() of another composite leaks: an observed outer composite outlives all of its sources","articleBody":"### Version\n\nv26.10.0 and v26.11.1.\n\n### Platform\n\nLinux arm64.\n\n### Subsystem\n\nlib (abortcontroller)\n\n### What steps will reproduce the bug?\n\nRun `node --expose-gc repro.mjs`:\n\n```js\n// node --expose-gc e3.mjs\nconst sleep = ms => new Promise(resolve => setTimeout(resolve, ms));\nconst collect = async () => { for (let round = 0; round \u003c 4; round++) { await sleep(10); globalThis.gc(); } };\nfor (const nested of [false, true]) {\n  let sources = [];\n  const handed = [];\n  for (let i = 0; i \u003c 8; i++) {\n    (() => {\n      const a = new AbortController();\n      const b = new AbortController();\n      sources.push(a, b);\n      const composite = nested ? AbortSignal.any([a.signal, AbortSignal.any([b.signal])]) : AbortSignal.any([a.signal, b.signal]);\n      const payload = new Uint8Array(2 ** 20);\n      composite.addEventListener(\"abort\", () => payload.fill(1));\n      handed.push(new WeakRef(composite));\n    })();\n  }\n  // While the sources live, nothing holds the inner composite, which a collection takes first.\n  await collect();\n  sources = undefined;\n  await collect();\n  console.log(`nested: ${nested}; ${handed.filter(ref => ref.deref() !== undefined).length}/8 composites alive once their sources were collected`);\n}\n```\n\n### How often does it reproduce? Is there a required condition?\n\nAlways: 5 of 5 runs on each version, when the inner composite is collected before its sources, as the repro arranges. If the order is left to the collector, it reproduces only sometimes.\n\n### What is the expected behavior? Why is that the expected behavior?\n\n`nested: true; 0/8 composites alive`, the same as `nested: false`. Once every source of a composite is gone, nothing can abort it, so its listener, and what the listener holds, should go too.\n\n### What do you see instead?\n\n`nested: true; 8/8 composites alive`: each outer composite, with its listener and the 1 MiB it holds, stays reachable for good.\n\n### Additional information\n\n`AbortSignal.any()` follows an inner composite's sources directly. The outer composite's clean-up seems to be tied to the inner composite, so collecting the inner one first leaves the outer one in `gcPersistentSignals` with no source left to release it.\n","author":{"url":"https://github.com/rinarakaki","@type":"Person","name":"rinarakaki"},"datePublished":"2026-10-08T17:28:27Z","url":"https://github.com/nodejs/node/issues/66612"}