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

#define dumpptr(P) printf("%u\n", (unsigned int) (P));

typedef struct TreeNode {
	int label;
	struct TreeNode* next;
} TreeNode;


TreeNode* treenode_new(int l, TreeNode* v) {
	TreeNode* t;
	t = malloc(sizeof(TreeNode));
	t->label = l;
	t->next = v;
	return t;
}

TreeNode** treenode_find_blank(TreeNode* t) {
	
	/* gets the address of root */
	TreeNode** q = &t;
	while (*q) {
		/* gets pointer to the pointer to next */
		q = &((*q)->next);
	}
	
	return q;
	
}

int main (void) {

	TreeNode* a;
    TreeNode** dest;

	/* creates root node */
	a = treenode_new(0, NULL);
	a->label = 10;
	
	/* find first blank node*/
	dest = treenode_find_blank(a);
	
	/* sets the destination node to a new node */
	*dest = treenode_new(1, NULL);
	
	/* next equals to dereferenced dest */
	dumpptr(a->next);
	dumpptr(*dest);
	
	return 0;
}