why am I getting segmentation fault when I alloc a 2048 * 2048 int array in c

Question

Alloc N * N int array in C, When N = 1024, It Just Workd, When N = 2048, I get "segmentation fault ". The machine is Ubuntu 20.04 with 2GB memory. Is my memory not big enough?

     1  #include <stdio.h>
     2
     3  #define N 1024
     4
     5  int main()
     6  {
     7      int arr[N][N];
     8
     9      for (int i = 0; i < N; i++)
    10          for (int j = 0; j < N; j++)
    11              arr[i][j] = i + j;
    12
    13      return 0;
    14  }

Answer 1

Put the decleration of arr outside of main. As it is now you are running out of stack space.

Answer 2

The declaration

int arr[N][N]

Is allocated on the stack of memory, which is very limited.

You need to allocate on the heap part of the memory

int *arr = (int*)malloc(N * N * sizeof(int));

By the C documentation, malloc always allocate more memory than the request and do this in the heap part of the memory.