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

	/*
	 *  realloc() takes two arguments: address to modify, # of bytes needed
	 *  # of bytes will equal: (new # of elements) * (sizeof(data type))
	 *
	 *  NOTE: realloc() will return a pointer to resized block of memory
	 *  (May be different from previous address)
	 *  Elements from initial block of memory will be preserved in the newly
	 *  resized array up to the intial # of elements
	 *  - All newly allocated elements will contain garbage
	 *  - Downsizing the array can result in lost data
	 *
	 *  ADDITIONAL NOTE: If succesful - and new block of memory was required -
	 *  previous array is freed from memory
	 *  Otherwise realloc() returns NULL
	 */

	int main(void) {

		// Take this int * arr of initial size 10
		// Each element initialized to 0 during calloc()
		int initialSize = 10;
		int *arr = (int *)calloc(initialSize, sizeof(int));

		// realloc can double the size of the previous array
		// IMPORTANT NOTE: If realloc() fails, it returns NULL
		// arr = realloc(arr, (initialSize * 2) * sizeof(int)); ---> DANGEROUS
		// If realloc() returns NULL, the original array still exists
		// but pointer to the array is set to NULL (A.k.A. Memory Leak)
		// and all access to the data is lost
		// INSTEAD use a temporary pointer:
		int *temp = realloc(arr, (initialSize * 2) * sizeof(int));

		// Now temp either points to newly resized array (twice its previous size)
		// OR it points to NULL
		// So check:
		if (temp) // Also can be written as if(temp != NULL)
			arr = temp;
		else
			printf("Failed to reallocate memory\n");

		// If realloc() failed arr still points to original array
		// and temp points to NULL

		// If realloc() succeeds - and new block of memory was required to resize -
		// previous block of memory will be freed automatically

		/////////////////////////////////////////////////////////////////////////////
		free(arr);

		printf("I hope this has helped to teach you how realloc() works :)\n");

		return 0;
	}