static void mainRunLoop()

in libs/core---vm/scheduler.cpp [399:468]
69 lines of code
23 McCabe index (conditional complexity)

static void mainRunLoop() {
    FiberContext *f = NULL;
    for (;;) {
        if (panicCode)
            return;
        wakeFibers();
        auto now = current_time_ms();
        auto fromBeg = false;
        if (!f) {
            f = allFibers;
            fromBeg = true;
        }
        while (f) {
            if (f->wakeTime && now >= (int)f->wakeTime)
                f->wakeTime = 0;
            if (!f->wakeTime && !f->waitSource)
                break;
            f = f->next;
        }
        if (f) {
            if (currentFiber != f) {
                saveStack();
                currentFiber = f;
                restoreStack();
            }
            f->pc = f->resumePC;
            f->resumePC = NULL;
            if (f->wakeFn) {
                auto fn = f->wakeFn;
                f->wakeFn = NULL;
                f->r0 = fn(f->wakeFnArg);
                if (f->wakeTime || f->waitSource)
                    continue; // we got suspended again
            }
            exec_loop(f);
            if (panicCode)
                return;
            auto n = f->next;
            if (f->resumePC == NULL) {
                if (f->foreverPC) {
                    f->resumePC = f->foreverPC;
                    f->wakeTime = current_time_ms() + 20;
                    // restore stack, as setupThread() does it
                    for (int i = 0; i < 5; ++i) {
                        if (*--f->sp == TAG_STACK_BOTTOM)
                            break;
                    }
                    if (*f->sp != TAG_STACK_BOTTOM)
                        target_panic(PANIC_INVALID_IMAGE);
                } else {
                    auto hb = f->handlerBinding;
                    if (hb) {
                        auto pev = hb->pending;
                        if (pev) {
                            hb->pending = pev->next;
                            setupThread(hb->action, fromInt(pev->value), hb);
                            xfree(pev);
                        } else {
                            f->handlerBinding->flags &= ~HANDLER_RUNNING;
                        }
                    }
                    disposeFiber(f);
                }
            }
            f = n;
        } else if (fromBeg) {
            target_yield();
        }
    }
}