Cooperative Synchronization#

index.nct is the checked public contract for shared ownership and synchronization. This guide explains its execution boundary and ownership rules.

Nocter sync values coordinate asynchronous computations scheduled cooperatively on one executor thread. Mutex<T> therefore protects logical task interleaving; it is not an atomic cross-thread mutex and must not be passed through a foreign-thread boundary. share is explicit because each returned handle participates in the lifetime of one page-backed value.

lock waits through the executor's descriptor-readiness contract. It neither spins nor blocks the executor thread. The returned MutexGuard<T> is the only public capability that exposes the value, and its destruction releases the mutex on ordinary return, failure propagation, and future cancellation. Notification bytes only prompt another state check; they never represent lock state.

Channel<T, N>.bounded() creates a queue whose positive capacity N is part of its type. Calling split consumes that new channel and returns its initial sending and receiving endpoints. Construction performs every allocation and descriptor operation; later sends, receives, endpoint clones, and wakeups do not grow storage. try_send returns an unsent value on a full or receiver-closed channel. send applies executor-friendly backpressure and returns the value only if every receiver closes. A sent value's storage origins must be contained by the sender, and a received value remains bounded by the receiver. This prevents a short-lived borrow from escaping through shared queue storage. Receivers distinguish temporary emptiness from final sender closure.

CancellationSource is the unique capability that changes cancellation state. token returns a clonable observer, cancel is idempotent, and destroying the source requests cancellation so a remaining token cannot wait forever for an owner that no longer exists. cancelled uses the same executor readiness path as mutex and channel waits. Cancellation is a cooperative request: it does not interrupt code, detach a task, or suppress ordinary owned-value destruction.

The checked contract marks handle cloning, cancellation state changes and inspection, and non-waiting channel attempts as noalloc. Construction owns every mapping and descriptor needed by those operations. Asynchronous waits still construct ordinary owning computations, but driving one does not grow the channel buffer or create a second notification authority.