How to allocate more memory to C code

Question

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

int main(int argc, char **argv)
{
    long int length = atol(*++argv);

    long int a[length];

    // write and read it, so it doesn't get optimized out:
    for (int i = 0; i < length; ++i)
        a[i] = i;    
    for (int i = 0; i < length; ++i)
        if (a[i] != i)
            return 1;
}

The program above runs in most cases, however when I try to initialise the array a with a large number (such as 1967791 ) I get a segmentation fault. Is there a way I can allocate more memory to the program so this doesn't happen?

I am running this program on a Virtual Machine using Linux.

Answer 1

You need to allocate memory on the heap, rather than on the stack:

  long int *a = malloc(array_length * sizeof *a);

Don't forget to free() it when it's no longer needed.