Question

How do I create an int array of size 20 MB?

Do I have to use malloc or sbrk or something else?

Answer 1

malloc is usually a good idea if you want something like 20MB. Most stacks are smaller and will crash the program if you try.

int *myInts = (int *)malloc(20*1024*1024);

or place it as a static/global variable:

int myArray[20*1024*1024/sizeof(int)];

or with sbrk

int *myInt = sbrk(0); /* Get the current pointer */
sbrk(20*1024*1024); /* Now increase it */

But as the man page says “avoid using sbrk“. The only time you should be using sbrk is if you are implementing your own memory allocator.