#include <stdio.h>    /* C example */
#include <stdlib.h>   /* for malloc and free */

struct node {         /* a node on a doubly linked list */
	int value;
	struct node *prev;
	struct node *next;
};

int main(int argc, char **argv)
{
	struct node *const p = malloc(sizeof (struct node));
	if (p == NULL) {
		fprintf(stderr, "%s: can't allocate %u bytes\n", /* not portable */
			argv[0], sizeof (struct node));
		return EXIT_FAILURE;
	}

	p->value = 10;
	p->prev = p->next = NULL;

	printf("value == %d, prev == %p, next == %p.\n",
		p->value, p->prev, p->next);

	printf("A struct node occupies %u bytes.\n", sizeof (struct node));
	printf("The hidden numbers are %u and %u.\n", /* unofficial; not portable */
		((size_t *)p)[-2], ((size_t *)p)[-1]);

	free(p);
	return EXIT_SUCCESS;
}