fs: fs.watch on MacOS leaks native memory each time a directory watcher is closed and reopened #67284

    import { watch, mkdtempSync, mkdirSync } from 'node:fs';
    import { tmpdir } from 'node:os';
    import { join } from 'node:path';
    import { execFileSync } from 'node:child_process';

    const footprintKB = () => {
      const out = execFileSync('vmmap', ['--summary', String(process.pid)]).
  toString();
      const [, n, unit] = out.match(/Physical footprint:\s+([\d.]+)([KMG])/);
      return Number(n) * { K: 1, M: 1024, G: 1024 * 1024 }[unit];
    };
    const tick = () => new Promise((r) => setImmediate(r));
    const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

    for (const n of [10, 100, 400, 1000]) {
      const base = mkdtempSync(join(tmpdir(), 'fsw-'));
      const dirs = Array.from({ length: n }, (_, i) => join(base, `d${i}`));
      for (const d of dirs) mkdirSync(d);
      const watchers = dirs.map((d) => watch(d, () => {}));
      await sleep(500);
      const before = footprintKB();
      for (let i = 0; i < 1000; i++) {
        watchers[0].close();
        watchers[0] = watch(dirs[0], () => {});
        if (i % 20 === 0) await tick();
      }
      await sleep(500);
      const growth = footprintKB() - before;
      console.log(`${n} watchers open: +${(growth / 1024).toFixed(1)} MB after
  1000 reopens (${(growth / 1000).toFixed(1)} KB per reopen)`);
      for (const w of watchers) w.close();
      await sleep(500);
    }
    process.exit(0);