Telling a function how many parameters it receives

[Powdertrail]

Hello. I'm having problems with a procedure:

void queue_destroy (queue_t* queue, void destroy_data(void*))

What I ought to do is: if queue_destroy receives just the queue, delete the queue as I know how. If I receive also a certain void*, I ought to call destroy_data instead.

How can I have the function queue destroy ask itself if it's receiving two parameters?

EDIT: destroy_data works like free().

[SamuelAdams]

Sounds like you would want to do that before you send it to your function.

[AbstractionAnon]

What you need to do is change the second argument to an optional function pointer.

// Prototype
void queue_destroy (queue_t* queue, void (*destroy_data)(void*) = nullptr);

Now you can test if the second argument was supplied by comparing it to nullptr.

 
// Implementation
void queue_destroy (queue_t* queue, void (*destroy_data)(void*))
{  if (destroy_data != nullptr)
    (*destroy_data) (queue);  
}