problem with qsort and array via calloc

Hello there,

I am having the following problem.

I am making an array of structures.
The struct contains an int.
I give this struct array to qsort to sort the struct array according to this int.
This works if I create the struct array like

struct Point track[] = { {5}, {4}, {3} };

for example.

However, I need to have a variable array size and therefore I want to use calloc.
But if I create the struct array via calloc, qsort won't sort anymore.

See bellow for the code that reproduces my problem.

If I use the calloc part instead, qsort won't sort.

Any ideas what's going on?

Thanks.

Code:

#include <stdio.h>
#include <stdlib.h>

struct Point { int x; };

int Point_cmp(const void *a, const void *b)
{
    struct Point *ia = (struct Point *)a; 
    struct Point *ib = (struct Point *)b;
    return ia->x  - ib->x; 
}


main() {
  size_t m = 4;
  struct Point Circle[] = { {4}, {1}, {0}, {-1} };
  //struct Point * Circle = NULL;
  //Circle = (struct Point *) calloc( m, sizeof(struct Point));

  size_t i;
  for ( i = 0; i < m; i++ ) {
    Circle[i].x = 100 - i;
  }

  for ( i = 0; i < m; i++ ) {
    printf("%d ",Circle[i].x);
  }
  printf("\n");

  size_t Circle_leng = sizeof(Circle)/sizeof(struct Point);
  qsort(Circle, Circle_leng, sizeof(struct Point), Point_cmp);

  for ( i = 0; i < m; i++ ) {
    printf("%d ",Circle[i].x);
  }
  printf("\n");


  return 0;
}

The problem lies here:

Code:

size_t Circle_leng = sizeof(Circle)/sizeof(struct Point);

This works for determining the number of elements of the array Circle when it is indeed an array of struct Point, but when it is a pointer, sizeof(Circle) gives the size in bytes of the pointer, not the array.

From what I see, you can just use m instead.

Yuhooo, you are right.