Task Scheduler Files

v4.0.4: 2025-11-15:

    - bug: set callbacks should not be available for _TASK_OO_CALLBACKS mode

v4.0.5: 2026-04-16:

    - bug fix: use-after-free in Scheduler::execute() when a callback destroys
      the next task in the chain (e.g. painlessMesh BufferedConnection teardown).
      Promoted nextTask to scheduler member iNextExecute so deleteTask() can
      advance it before the memory is freed.

v4.0.6: 2026-04-17:

    - bug fix: thread-safe setSelfDestruct request called wrong function
      (setSchedulingOption instead of setSelfDestruct)
    - bug fix: NULL pointer dereference in disable() when iScheduler is NULL
      (triggered when a still-enabled task is removed via deleteTask then destroyed)
    - bug fix: dangling pointer in disableAll() and enableAll() -- applied the
      same iNextExecute pattern used in execute() to protect against callbacks
      that destroy the next task in the chain
    - bug fix: missing NULL check on iStatusRequest in execute() status request
      handling -- could crash if waiting flag was set but no StatusRequest assigned
    - added NULL safety to currentLts() and isOverrun() public API methods
    - initialized iActiveTasks/iTotalTasks/iInvokedTasks in Scheduler::init()
    - clarified assignment-in-condition in StatusRequest::signal()
    - added documentation comments for known limitations: thread-safe request
      pointer lifetime, millis() rollover in tickless mode, signed overflow in
      overrun calculations, execute() re-entrancy, pointer truncation on >32-bit

v4.0.7: 2026-04-17:

    - feature: deprecated currentTask() now returns a safe sentinel instead of
      crashing when called outside a task callback (iCurrent == NULL)
    - feature: added getChainLength() method to Scheduler -- returns the number
      of tasks in the chain at any time, without requiring an execute() pass.
      Maintained via O(1) counter in addTask/deleteTask.

v4.0.8: 2026-04-20:

    - bug fix: Scheduler::currentTask() failed to compile under _TASK_OO_CALLBACKS
      because the static Task sDummy sentinel introduced in v4.0.7 cannot be
      instantiated (Task is abstract when OO callbacks are enabled -- Callback()
      is pure virtual). Replaced with a local concrete subclass that stubs out
      Callback() in OO mode; function-pointer mode path is unchanged.
    - example: Scheduler_example21_OO_Callbacks -- silenced signed/unsigned
      compare warning in SuperSensor::measurementReady() by casting iDelay to
      unsigned long.