Question

I have a 2-dimensional array and I am passing it into a function to carry out certain operations. I’d like to know the correct way of doing it…

#define numRows 3
#define numCols 7
#define TotalNum (numRows*numCols)
int arr[numRows][numCols] = {{0,1,2,3,4,5,6}, {7,8,9,10,11,12,13},{14,15,16,17,18,19,20}};

void display(int **p)
{
    printf("\n");
    for (int i = 0; i< numRows;i++)
    {
        for ( int j = 0;j< numCols;j++)
        {
            printf("%i\t",p[i][j]);
        }
        printf("\n");
    }
}

int main() {
    display(arr);
}

I get an error message:

'display': cannot convert parameter1 from 'int' to 'int*'

Is this the correct way of passing a 2-dimensional array into a function? If not, what is the correct way?

Answer 1

You should declare your function like this:

void display(int p[][numCols])

This C FAQ thoroughly explains why. The gist of it is that arrays decay into pointers once, it doesn’t happen recursively. An array of arrays decays into a pointer to an array, not into a pointer to a pointer.