uscxml-transform generated statemachine dequeues _event before transitions

[larry104]

Maybe someone can help who uses statemachines generated by uscxml-transform, I am playing with what was published here. If you look at the scxml statemachine he lists line 25/26 he defines a transition with a cond element accessing _event->data.

If you look at the dequeueExternal method he defines:
static void* dequeueExternal(const uscxml_ctx* ctx) { ...}

_event gets set to NULL.

BUT The statemachine invokes first dequeueExternal before it does the transition handling
if (ctx->dequeue_external != NULL && (ctx->event = ctx->dequeue_external(ctx)) != NULL) {
goto SELECT_TRANSITIONS;
}

Thus when
SCXML_GET_TRANS(i).is_enabled(ctx, &USCXML_GET_TRANS(i)) > 0)) is called in the transition handling which does the actual evaluation of the cond e.g. _event->data.light > LIGHT_THRES it will fail because_event was just set to NULL.

That being said the example he posts actually does not work. So, what is the proper way to access _event->data or _event->name inside a transition condition? Or what is the proper way of defining dequeueExternal/dequeueInternal?

Any help would be appreciated a lot!
Thanks!

[larry104]

I did a bit more digging ... when using a cond in a transition e.g.

The complied statemachine.c file contains the following struct for this transition

static const uscxml_transition _uscxml_936B479C__transitions[1] = {
{ /* transition number 0 with priority 0
target: LATCH
/
/ source / 1,
/ target / { 0x04 / 001 / },
/ event / "TEST",
/ condition / NULL,
/ is_enabled / _uscxml_936B479C__FLASH_transition0_is_enabled,
/ ontrans / NULL,
/ type / 0,
/ conflicts / { 0x01 / 1 / },
/ exit set / { 0x06 / 011 */ }
}
};

There is the following if statement in uscxml_step

if ((ctx->event == NULL || ctx->is_matched(ctx, &USCXML_GET_TRANS(i), ctx->event) > 0) &&
(USCXML_GET_TRANS(i).condition == NULL ||
USCXML_GET_TRANS(i).is_enabled(ctx, &USCXML_GET_TRANS(i)) > 0)) {

Since USCXML_GET_TRANS(i).condition == NULL the actual call to the is_enabled method will never get called. Thus cond in a transition will never work. Do I miss anything here?