多个__COUNTER__ C

Question

I'm playing around with the preprocessor and c. Trying to implement my own event and hierarchy system. However I'm facing a problem. I'm trying to statically define my "modules" which can be initialized, and some events which also are statically defined in advance. For the events I'm using COUNTER which works beautiful. But I don't want to mix up module id's and event id's.

So a simplified version of what I'm trying to achieve:

hierarchy.h

#define HIERARCHY_DEFINE(NAME) int hierarchyId = __COUNTER__

event.h

#define EVENT_REGISTER(NAME) int eventId = __COUNTER__

main.c

#include "event.h"
#include "hierarchy.h"

EVENT_REGISTER(EventOne);
HIERARCHY_DEFINE(ModuleOne);
EVENT_REGISTER(EventTwo);

int main(void){
    printf("events(%d, %d) modules(%d)\n",EventOne,EventTwo,ModuleOne);
    return 1;
}

This will print out:

events(0, 2) modules(1)

When I'm trying to achieve:

events(0, 1) modules(0)

I've looked around and people saying I can't create a counter on my own. And seen the boost counter, but that doesn't achieve what I want either.

Does anybody have an idea how I could handle this situation?

Thanks!

Edit:

slight adition of what my code actually looks like

struct Event{
    uint8_t eventId;
    uint8_t * data;
    const char * description;
};

#define EVENT_REGISTER(eventName, desc)\
static Event eventName = {.eventId = __COUNTER__, .data = 0, .description = desc }




EVENT_REGISTER(Timer_5, "Timer 5 hZ");

Answer 1

Unless you have additional requirements for the identifiers, the following will do:

definitions.inc

EVENT_REGISTER(Timer_5, "Timer 5 Hz")
EVENT_REGISTER(Timer_10, "Timer 10 Hz")
MODULE_REGISTER(Module_SSH)
MODULE_REGISTER(Module_NCO)
#undef EVENT_REGISTER
#undef MODULE_REGISTER

app.c

#define EVENT_REGISTER(a, d) a,
#define MODULE_REGISTER(a)
enum events {
#include "definitions.inc"
};

#define EVENT_REGISTER(a, d)
#define MODULE_REGISTER(a) a,
enum modules {
#include "definitions.inc"
};

struct Event {
    uint8_t event_id;
    uint8_t *data;
    const char *description;
};

#define MODULE_REGISTER(a)
#define EVENT_REGISTER(a, d) static struct Event Event_##a = { .event_id = a, \
    .data = NULL, \
    .description = d \
};
#include "definitions.inc"


int main (int argc, char **argv)
{
    printf("events(%d, %d) modules(%d)\n", Timer_10, Timer_5, Module_SSH);

    return EXIT_SUCCESS;
}

Answer 2

You must either:

• assign ids at runtime,
• assign ids by hands
• or keep all events and modules definitions in one place.

Consider that you have ac and bc , and they contains some EventA and EventB definitions respectively. As they are separate compilation units, there is no way compiler can assign non-overlapping ids to them. Compiling bc , it doesn't even know there is another ac where id 1 is already assigned.

For the first one, have a RegisterEvent function like so:

void RegisterEvent(Event* event){
  static int nextEventId = 0;
  event->eventId = nextEventId;
}

And call it for every Event you need.

Second one is obvious, but tedious and error prone.

For the third solution, you can use an X macro .

Have a X-list of all your events:

#define EventList \
  Event(FirstEvent, "FirstEvent") \
  Event(Timer_1, "Timer 1 hZ") \
  ... 
  Event(Timer_5, "Timer 5 hZ")

Now, in a header there you are going to declare all your events (say, events.h ):

#define Event(name, desc) EventID ## name,
enum EventID{
 EventIDZero = 0,
 EventList 
 EventIDCount
};
#undef Event

#define Event(name, desc) \
  extern Event name;
EventList
#undef Event

And in a single compilation unit where your event definitions will reside (say, events.c ):

#include "events.h"

#define Event(name, desc) \
  Event name = {.eventId = EventID ## name, .data = 0, .description = desc };
EventList
#undef Event

After macro expansion, events.c looks like (slightly edited for readability):

enum EventID{
 EventIDZero = 0,
 EventIDFirstEvent, EventIDTimer_1, EventIDTimer_5,
 EventIDCount
};

extern Event FirstEvent; 
extern Event Timer_1; 
extern Event Timer_5;

Event FirstEvent = {.eventId = EventIDFirstEvent, .data = 0, .description = "FirstEvent" }; 
Event Timer_1 = {.eventId = EventIDTimer_1, .data = 0, .description = "Timer 1 hZ" }; 
Event Timer_5 = {.eventId = EventIDTimer_5, .data = 0, .description = "Timer 5 hZ" };

Same thing goes for modules.