@@ -49,6 +49,16 @@ static recurrent_fn_t* rLast = nullptr;
4949// The target time for scheduling the next timed recurrent function
5050static decltype (micros()) rTarget;
5151
52+ // As 32 bit unsigned integer, micros() rolls over every 71.6 minutes.
53+ // For unambiguous earlier/later order between two timestamps,
54+ // despite roll over, there is a limit on the maximum duration
55+ // that can be requested, if full expiration must be observable:
56+ // later - earlier >= 0 for both later >= earlier or (rolled over) later <= earlier
57+ // Also, expiration should remain observable for a useful duration of time:
58+ // now - (start + period) >= 0 for now - start >= 0 despite (start + period) >= now
59+ // A well-balanced solution, not breaking on two's compliment signed arithmetic,
60+ // is limiting durations to the maximum signed value of the same word size
61+ // as the original unsigned word.
5262constexpr decltype (micros()) HALF_MAX_MICROS = ~static_cast<decltype(micros())>(0 ) >> 1;
5363
5464// Returns a pointer to an unused sched_fn_t,