Resolving an awaited Promise with an empty Uint8Array segfaults on windows

[jroweboy]

What happened

Resolving an awaited Promise with an empty Uint8Array segfaults on windows

What you expected

No segfault hopefully :)

Minimal reproduction

function collectBytes(): Promise<Uint8Array> {
  return new Promise((resolve) => {
    const chunks: Uint8Array[] = [];
    process.stdin.setRawMode(true);
    process.stdin.on('data', (chunk: Uint8Array | string) => {
      chunks.push(typeof chunk === 'string' ? new TextEncoder().encode(chunk) : chunk);
    });
    process.stdin.on('end', () => {
      let total = 0;
      for (const c of chunks) total += c.length;
      const out = new Uint8Array(total); // total === 0 -> empty Uint8Array
      let offset = 0;
      for (const c of chunks) { out.set(c, offset); offset += c.length; }
      resolve(out); // <- segfaults when out.length === 0
    });
    process.stdin.resume();
  });
}

async function main() {
  const bytes = await collectBytes();
  console.log('len=' + bytes.length);
}

main();

Command you ran:

(Due to #5000 which affects reading from stdin as well, I have the perry source locally, and i have to build with PERRY_WORKSPACE_ROOT)

PERRY_WORKSPACE_ROOT=/path/to/perry/ perry compile perry-bug-empty-uint8array-resolve.ts -o ./perry-bug-empty-uint8array-resolve.exe
printf '' | ./perry-bug-empty-uint8array-resolve.exe

Environment

• Perry version: perry 0.5.1167
• Host OS: Windows 11
• Target: native
• Rust toolchain (if building from source): rustc 1.96.0 (ac68faa20 2026-05-25)
• Installed via: from source

Diagnostic output

$ printf "" | ./build/perry-bug-empty-uint8array-resolve.exe
Segmentation fault         printf "" | ./build/perry-bug-empty-uint8array-resolve.exe

Anything else

I found that just returning an empty string could work around this particular issue, but that's not a good long term plan for my usage.

[proggeramlug]

Thanks for the report, I'm on it :)