为什么不能打印存储在创建的数组中的值？

Question

So a user can create his square matrix and enter the desired values. The thing is that the matrix is created via a function and it seems that when the function is done with its task and we return to the main function and I try to reprint the elements of the matrix,to check if everything is ok again after the first printing inside the function, the program crashes. Have in mind that I'm using pointers only and not []s. Also the size variable is going to be used in functions that check various properties of the matrix(sparse etc) so that's why I use it like this.

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

int CreateArray(int **ptr);

int main()
{
    int **ptr = NULL;
    int size = 0;
    int i,j;

    size = CreateArray(ptr);

     for(i=0;i<size;i++)
    {
        for(j=0;j<size;j++)
        {
            printf("%d",*(*(ptr+i)+j));
            if(j == (size-1))
            {
                printf("\n");
            }
        }
    }




    system("PAUSE");
    return 0;
}


int CreateArray(int **ptr)
{
    int i=0;
    int j=0;
    int size = 0;

    printf("Input the size of your square matrix\n");
    scanf("%d", &size);

    ptr = malloc(sizeof(int*)*size);

    for(i=0; i< size; i++)
    {
        *(ptr + i) = malloc(sizeof(int)*size);
    }

    printf("Enter the values to be stored in your array\n");
    for(i=0;i<size;i++)
    {
        for(j=0;j<size;j++)
        {
            scanf("%d", &*(*(ptr+i)+j));
        }
    }

    for(i=0;i<size;i++)
    {
        for(j=0;j<size;j++)
        {
            printf("%d",*(*(ptr+i)+j));
            if(j == (size-1))
            {
                printf("\n");
            }
        }
    }

    return size;

}

Answer 1

Your pointer is passed by value. If you want to modify from within the function, you need to pass its address. You then need to re-adjust all lines within CreateArray that accessed ptr to dereference it once more:

int main()
{
    int **ptr = NULL;
    int size = 0;
    int i,j;

    size = CreateArray(&ptr);

    for(i=0;i<size;i++)
    {
        for(j=0;j<size;j++)
        {
            printf("%d ",*(*(ptr+i)+j));
            if(j == (size-1))
            {
                printf("\n");
            }
        }
    }

    return 0;
}


int CreateArray(int ***ptr)
{
    int i=0;
    int j=0;
    int size = 0;

    printf("Input the size of your square matrix\n");
    scanf("%d", &size);
    *ptr = malloc(sizeof(int*)*size);

    for(i=0; i< size; i++)
    {
       *((*ptr) + i) = (int*)malloc(sizeof(int)*size);
    }

    printf("Enter the values to be stored in your array\n");
    for(i=0;i<size;i++)
    {
        for(j=0;j<size;j++)
        {
            scanf("%d", (*((*ptr)+i)+j));
        }
    }

    return size;
}