denoland/deno · critical

{}: ({}) {}

Error message

{}: ({}) {}

What it means

The Windows subprocess runtime ports libuv's fatal-error handling: when a process-control syscall fails, uv_fatal_error_with_no formats the syscall name, errno, and the message from FormatMessage, then panics because the subprocess state cannot be recovered.

Source

Thrown at runtime/subprocess_windows/src/process.rs:189

      0,
      null_mut(),
    );
  }
  let errmsg = if buf.is_null() {
    "Unknown error"
  } else {
    unsafe { CStr::from_ptr(buf).to_str().unwrap() }
  };

  let msg = if syscall.is_empty() {
    format!("({}) {}", errno, errmsg)
  } else {
    format!("{}: ({}) {}", syscall, errno, errmsg)
  };
  if !buf.is_null() {
    unsafe { LocalFree(buf.cast()) };
  }
  panic!("{}", msg);
}

fn uv_fatal_error(syscall: &str) {
  uv_fatal_error_with_no(syscall, None)
}

fn uv_init_global_job_handle() {
  use windows_sys::Win32::System::JobObjects::*;
  UV_GLOBAL_JOB_HANDLE.get_or_init(|| {
    unsafe {
      // SAFETY: SECURITY_ATTRIBUTES is a POD type, repr(C)
      let mut attr = mem::zeroed::<SECURITY_ATTRIBUTES>();
      // SAFETY: JOBOBJECT_EXTENDED_LIMIT_INFORMATION is a POD type, repr(C)
      let mut info = mem::zeroed::<JOBOBJECT_EXTENDED_LIMIT_INFORMATION>();
      attr.bInheritHandle = FALSE;

      info.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_BREAKAWAY_OK
        | JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Verify the executable path exists and is runnable before spawning
2. Reduce concurrency or check job-object limits on the CI runner
3. Read the errno in the panic message and map it to the Windows error code (e.g. 5 = access denied) to find the cause
4. Update Deno - more spawn failures are mapped to typed errors in newer versions

// Validate before spawn on Windows
fn spawnable(exe: &str) -> bool {
  let p = std::path::Path::new(exe);
  p.is_file()
}
if !spawnable(&cmd) {
  return Err(format!("executable not found: {cmd}")); // normal error, no panic
}

When it happens

Trigger: Spawning a child process on Windows where the OS call fails: invalid spawn attributes or handles, job-object limits reached, or required system resources exhausted in a way not pre-checked by a typed error.

Common situations: Process spawning on constrained CI runners (job limits), antivirus interference, or programmatically produced invalid spawn arguments.

Related errors

• failed to unregister: {}
• Initialize libloading failed {}
• nul byte found in provided data
• Process not found
• Invalid arguments

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/2fba657dde4b2313. Report an issue: GitHub.