Dynamic memory allocation for 2D arrays (C) - c

Question

I've noticed that I lack of knowledge of dynamic 2D arrays, after reading some topics here and around the web I've tried something but it seem not to behave correctly:
I want to allocate a 3X3 array of integers, input values in to it and display them, the problem is that always after I enter a value at the index of [3][1] the program crashes... it is weird because I think that I've done everything correctly.
I would also like to hear your thoughts about checking for memory allocation failure,(!(array)) good enough method? I've also seen some examples of deallocating memory up to the failure point, if one occurred.
#include <stdio.h>
#include <stdlib.h>
int main()
{
int i, j, //loop control
**array, //pointer to hold the 2D array
N = 3; //rows and columns quantity
array = malloc (N * sizeof (int*)); //allocating rows
if (!(array)) //checking for allocation failure
{
printf("memory allocation failed!\n");
goto exit;
}
else
{
array [i] = calloc (N, sizeof (int)); //allocating columns
if (!(array[i])) //checking for allocation failure
{
printf("memory allocation failed!\n");
goto exit;
}
}
for (i = 0; i < N; i++) //getting user input
{
for (j = 0; j < N; j++)
{
printf("Enter value [%d][%d]:", i+1, j+1);
scanf ("%d", &array [i][j]);
}
}
for (i = 0; i < N; i++) //displaying the matrix
{
printf("\n");
for (j = 0; j < N; j++)
{
printf (" %d", array [i][j]);
}
}
exit:
return 0;
}

Answer 1

You have couple of problems.
You are using uninitialized i.
You haven't allocated memory for all the rows. The following line can allocate memory for only one row.
array [i] = calloc (N, sizeof (int)); //allocating columns
What you need:
Instead of
array [i] = calloc (N, sizeof (int)); //allocating columns
if (!(array[i])) //checking for allocation failure
{
printf("memory allocation failed!\n");
goto exit;
}
Use
for ( i = 0; i < N; ++i )
{
array [i] = calloc (N, sizeof (int)); //allocating columns
if (!(array[i])) //checking for allocation failure
{
printf("memory allocation failed!\n");
goto exit;
}
}

Answer 2

You got lucky it didn't crash earlier. You only allocated one row of the 3x3 matrix:
array [i] = calloc (N, sizeof (int)); //allocating columns
if (!(array[i])) //checking for allocation failure
{
printf("memory allocation failed!\n");
goto exit;
}
You need to do this for each row of the matrix, not just once.
Furthermore, when you call calloc, the value of i is undefined. Wrapping the above block in a foor loop should fix your issue:
else
{
for (i = 0; i < N; i++) {
array [i] = calloc (N, sizeof (int)); //allocating columns
if (!(array[i])) //checking for allocation failure
{
printf("memory allocation failed!\n");
goto exit;
}
}
}