TimeEvent_ctor question

[marcosCapistrano]

void TimeEvent_ctor(TimeEvent * const me, Signal sig, Active *act) {
    /* no critical section because it is presumed that all TimeEvents
     * are created *before* multitasking has started.
     */
    me->super.sig = sig;
    me->act = act;

    /* Create a timer object */
    me->timer = xTimerCreateStatic("TE", 1U, me->type, me,
                                   TimeEvent_callback, &me->timer_cb);
    configASSERT(me->timer);            /* timer must be created */
}

Im not well versed on C so forgive me if this is a dumb question,

• since the constructor does not accept a type, how would we set it to anything different?
• wouldn't not initializing it explicitly possibly cause problems if the type isnt zero by default? (when using malloc for example)

[quantum-leaps]

Hi Marcos,
Thank you for your interest in Active Objects and the "FreeACT" implementation.

Frankly, I don't quite understand your problems/questions. But here is what I think you're asking about:

since the constructor does not accept a type, how would we set it to anything different?

The "constructor" of any class (not just TimeEvt) is always specific to the class it initializes. Therefore, the class name is embedded in the "constructur's" name and the me pointer has that specific type. You cannot use such a "constructor" for any other class, so there is no way to "set it to anything different". Instead, for a different class you must provide a different constructor.

wouldn't not initializing it explicitly possibly cause problems if the type isnt zero by default? (when using malloc for example)

You are right that a constructor in a truly OO language (e.g., C++) typically handles both instantiation (allocating memory) and initialization. I've explained the OOP in C in the video playlist Object-Oriented Programming. But here shortly, the "constructors" in C in that OOP implementation only perform initialization of already allocated memory. This particular OOP in C implementation allows you to allocate memory any way you like, which includes malloc(). However, using heap memory in embedded systems is almost always a BAD idea (e.g., see article "A Heap of Problems").

Finally, regarding "FreeACT" specifically, it is a minimal framework with the main intent to show the basic principles. It was intended as an educational aid and not intended for use in real products.

I hope that my comments somewhat address your questions.