Heap memory

[Simon Izraev]

This code should create a cell in the heap memory.(creatBox function)
And afterwards the function addNumber should add cell to the first pointer(*box)
with the value that user input.
It dosnt work after compile. would love to get some help. where i got wrong?

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


unsigned int* createBox();
void destructBox(unsigned int* box_ptr);
unsigned int* addNumber( unsigned int* box_ptr, unsigned int number);


int main()
{

unsigned int* box;
box = createBox();

int a;
 for(a=0; a<10; a++)
 {
   box = addNumber( box, 2);

    printf("%d ", *(box+a));

 }


destructBox(box);
    return 0;
}

unsigned int* createBox()
{

    return calloc(1, 4);
}

void destructBox(unsigned int* box_ptr)
{
    free(box_ptr);
}

unsigned int* addNumber( unsigned int* box_ptr, unsigned int number)
{

  *box_ptr += 1;           
   int a=4*(*box_ptr);
   box_ptr = (unsigned int *)realloc(box_ptr, a);
   if(box_ptr==NULL)
    printf("no more memory");
 *(box_ptr+(*box_ptr)) = number;


   return box_ptr;

}

[Smac89]

You should be using the sizeof operator rather than just the magic number 4 (or what you have done on line 45) to indicate the number of bytes each element of the array is.

What exactly are you trying to do with your addNumber function?