How to create a 2D array in a function

Question

I've made a program that creates a 2D array in main, and passes the array to be populated. I'd like to create the array in a function for modularity and to keep main clean, s cut down version of my original code so far are:

int main(int argc, char *argv[])
{
    long iWidth;    /*Image width*/
    long **arr;     /*creating array to hold the black and white image*/

    <get width of a square image into iWidth>

    arr = mallocSafe(iWidth * sizeof *arr); /*Can dynamically allocate memory for the 3d array now width is known*/
    for (i=0; i < iWidth; i++)              /*allocate the array (rows)*/
    {
        arr[i] = mallocSafe(iWidth * sizeof *arr[i]); /*allocate the array (columns)*/
    }

    buildArr(iWidth, arr);
    ...
}


buildArr(iWidth, arr)
{  

    ...   

    for (x = 0; x < iWidth; x++) /*fills the array with white pixels*/
    {
        for (y = 0; y < iWidth; y++)
        {
            arr[x][y] = 0;
        }
    }
}

This works fine, but when I malloc and initialise the array in a separate function I get a segfault when I try to populate the array in the buildArray function. Clearly I don't understand arrays as well as I thought. Could someone point out where I'm going wrong? I've tried a few different ways, the latest is as follows:

int main(int argc, char *argv[])
{
    long iWidth;   /*Image width*/
    long **arr     /*creating array to hold the black and white image*/  
    createArray(arr, iWidth);  
    buildArr(iWidth, arr)
}


void createArray(long** arr, long size)
{
    int i;
    arr = mallocSafe(size * sizeof *arr);      /*Can dynamically allocate memory for the 3d array now width is known*/
    for (i=0; i < size; i++)                    /*allocate the array (rows)*/
    {
        arr[i] = mallocSafe(size * sizeof *arr[i]);      /*allocate the array (columns)*/
    }
}



buildArr(iWidth, arr)
{  

    ...   

    for (x = 0; x < iWidth; x++) /*fills the array with white pixels*/
    {
        for (y = 0; y < iWidth; y++)
        {
            arr[x][y] = 0;
        }
    }
}

Hopefully I've not made any errors in trying to make my code simpler to read!