Passing pointers to two-dimensional arrays of structs

Hi,

I have written a function which receives a pointer to a two-dimensional array of structs. To use the GNU Scientific Library (which is excellent) I need to wrap the function in another function of form:

void wrapper(void *)

How should I do this? The short but complete example below works but my compiler complains about an incompatible type:

main.c:18: warning: passing argument 1 of 'func' from incompatible pointer type
[refering to the func(z) line in wrapper()]

I think the problem is that "struct coord ** z" and "struct coord z[][]" are not of the same type. What is the right way to do this? The one-dimensional version compiles silently and works perfectly. All comments welcome!

Thanks,
Neil.

Code:

---


#include <stdio.h> 

struct coord {
  int x;
  int y;
};
 
void func(struct coord z[2][2])
{
  printf("%d,%d\n", z[0][0].x, z[0][0].y);
}
 
void wrapper(void * s)
{
    struct coord ** z;
   
    z = (struct coord **) s;
    func(z);
}
 
int main(void)
{
  struct coord b[2][2];
  void * c;
   
  b[0][0].x = 1;
  b[0][0].y = 2;
  b[0][1].x = 3;
  b[0][1].y = 4;
  b[1][0].x = 5;
  b[1][0].y = 6;
  b[1][1].x = 7;
  b[1][1].y = 8;
 
  func(b);

  c = (void *) b;
  wrapper(c);

  return 0;
}

---

A pointer to a pointer is not the same as a pointer to an array.
http://c-faq.com/aryptr/pass2dary.html - or thereabouts

Code:

---

#include <stdio.h> 

struct coord {
  int x;
  int y;
};
 
void func(struct coord z[2][2])
{
  printf("%d,%d\n", z[0][0].x, z[0][0].y);
}
 
void wrapper(void * s)
{
    struct coord (*z)[2] = s;
    func(z);
}
 
int main(void)
{
  struct coord b[2][2] = { { {1,2}, {3,4} }, { {5,6}, {7,8} } };
  func(b);
  wrapper(b);
  return 0;
}

---

Thank you Dave. Completely fixed - really helpful.