oven-sh/bun · error

Failed to create waker

Error message

Failed to create waker

What it means

Error "Failed to create waker" thrown in oven-sh/bun.

Source

Thrown at src/bundler/BundleThread.rs:194

        // `UnboundedQueue::push` takes `&self` (lock-free MPSC). `Waker::wake` takes
        // `&self` on all platforms and only reads a Copy field (eventfd, mach port,
        // `WindowsLoop` pointer) to pass to a wake call that is safe from any thread
        // (eventfd write, mach_msg send, uv_async_send), so the `&Waker` autoref is
        // sound alongside `wait(&self)` in `thread_main` and other `enqueue` callers.
        unsafe {
            (*instance).queue.push(completion);
            (*instance).waker.wake();
        }
    }

    unsafe fn thread_main(instance: *mut Self) {
        Output::Source::configure_named_thread(zstr!("Bundler"));

        // SAFETY: `waker` is written exactly once here, before `ready_event.set()`
        // releases any thread that could call `enqueue` (which reads `waker`).
        unsafe {
            core::ptr::addr_of_mut!((*instance).waker)
                .write(Async::Waker::init().unwrap_or_else(|_| panic!("Failed to create waker")));
        }

        // Unblock the calling thread so it can continue.
        // SAFETY: raw-ptr field projection; spawning thread is blocked in `ready_event.wait()`.
        unsafe { (*instance).ready_event.set() };

        // The libuv Timer lives on stack for the lifetime of this never-returning fn.
        // It MUST be declared at function scope (not inside the `#[cfg(windows)] { ... }`
        // block below) because `timer.init()`/`timer.start()` register `&timer`'s address
        // into the uv loop's intrusive handle queue / timer min-heap, and `waker.wait()`
        // (→ `uv_run`) in the `loop {}` below dereferences that address.
        #[cfg(windows)]
        let mut timer: bun_sys::windows::libuv::Timer = bun_core::ffi::zeroed();
        #[cfg(windows)]
        {
            // SAFETY: raw place read of `waker.loop_.uv_loop` (Copy ptr); field is
            // write-once in `Waker::init()` above and never mutated by `wake()`, so a
            // concurrent `enqueue()` (possible now that `ready_event.set()` has fired)

View on GitHub (pinned to 8c5296ac45)

When it happens

Trigger: Thrown at src/bundler/BundleThread.rs:194 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oven-sh/bun@8c5296ac45 (2026-08-16). Data as JSON: /api/errors/f7ecb71d2cea1e44. Report an issue: GitHub.