Passing a parameter via function pointer

[hzcodec]

Hi,
I'm trying to pass a parameter via a function pointer. My first attempt without a parameter works but when adding it, it fails.

So this is without an in parameter to the function pointer in checkPin():

#include <stdio.h>

void sayHello(void)
{
    printf("Hello\n");
}  

void checkPin(const int pin, void (*response)(void))
{
    if (pin == 0)
    {
       response();
    }
}
  
int main()
{
    checkPin(0, sayHello);    

    return 0;
}

And here I've added an int to the function:

#include <stdlib.h>
 
void sayHello(int a)
{
    printf("Hello\n");
}  

void checkPin(const int pin, void (*response)(int a))
{
    int a;
    if (pin == 0)
    {
       response(a);
    }
}
  
int main()
{
    checkPin(0, sayHello(10));    

    return 0;
}

I get a compile error pointing at the row checkPin(0, sayHello(10));

error: invalid use of void expression

And probably how to get the parameter information in checkPin() to response().

[hzcodec]

I actually came up with this solution. Maybe this is the way to do it?

#include <stdlib.h>
 
void sayHello(int a)
{
    printf("Hello: %d\n", a);
}  

void checkPin(const int pin, void (*response)(int a), int x)
{
    if (pin == 0)
    {
       response(x);  // call the callback function
    }
}
  
int main()
{
    checkPin(0, sayHello, 30);    

    return 0;
}

[laserlight]

Your solution looks fine to me.

[hzcodec]

OK, thanks for your comment.