/**
 * longTimeout — arm a host timer for a limit of any length.
 *
 * A host timer holds at most 2^31 − 1 ms (about 24.8 days). Node turns a longer
 * delay — `Infinity` included — into 1 ms, with a `TimeoutOverflowWarning`, so
 * a raw `setTimeout(fn, limit)` gives up at once exactly when the caller asked
 * to wait longest. The law, by the limit:
 *
 *   - `Infinity` — no limit: NO timer is armed and `fn` never runs, so nothing
 *     keeps the process alive on its account.
 *   - a finite delay past 2^31 − 1 ms — waited in chained chunks of at most
 *     2^31 − 1 ms, so it never fires early and never after 1 ms.
 *   - anything else that is not a number > 0 (`0`, a negative, `NaN`) — already
 *     due: `fn` runs on the next timer turn, as `setTimeout(fn, 0)` does.
 *
 * `{ unref: true }` unrefs every chunk, for a timer that only bounds a wait.
 * The returned function cancels whichever chunk is armed; it is a no-op when
 * nothing was armed.
 *
 * A COPY, ON PURPOSE: footprintjs has the same helper (`setLongTimeout`,
 * footprintjs#136) but keeps it private — it is not part of footprintjs's
 * public exports. agentfootprint keeps this copy, with the same signature and
 * the same law, until footprintjs exports a supported long-timer helper.
 *
 * A leaf: imports nothing.
 */
/** How a long timer is armed. */
export interface LongTimeoutOptions {
    /** Unref every host timer it arms (where the host has `unref`). */
    readonly unref?: boolean;
}
/** `setTimeout` for a limit of any length, by the law above. Returns its
 *  cancel. */
export declare function setLongTimeout(fn: () => void, ms: number, options?: LongTimeoutOptions): () => void;