Linked List generator in C

genlist.c

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

void init_list(struct list **p, unsigned tail, unsigned loop) {
	if (*p != NULL) {
		fprintf(stderr, "init_list: base pointer not NULL\n");
		return;
	}
	
	int n;
	struct list **tail_end = NULL;

	for (n=0; n<tail; ++n) {
		*p = malloc(sizeof(*p));
		(*p)->n = n;
		(*p)->next = NULL;
		p = &(*p)->next;
	}

	tail_end = p;

	for (; n<tail+loop; ++n) {
		*p = malloc(sizeof(*p));
		(*p)->n = n;
		(*p)->next = *tail_end;
		p = &(*p)->next;
	}
}

void printl(struct list *b, unsigned length) {
	int n;

	printf("linked list (size=%d):\n", length);
	for (n=0; n<length && b != NULL; ++n, b = b->next)
		if (b->next)
			printf("\tp_%u->next = p_%d\n", b->n, b->next->n);
		else
			printf("\tp_%u->next = NULL\n", b->n);
}

genlist.h

#ifndef GENLIST_H_
#define GENLIST_H_

struct list {
	struct list *next;	/* pointer to next item */
	unsigned	n;	/* number (for debug) */
};

/*
 * Initializes a list with a specified tail and loop length
 * @param p pointer to base pointer (assumed to be NULL)
 * @param tail length of tail
 * @param loop length of loop
 */
void init_list(struct list **p, unsigned tail, unsigned loop);

/*
 * Prints out a linked list (looped or unlooped) with length.
 * @param b base pointer
 * @param length absolute length of list
 */
void printl(struct list *b, unsigned length);

#endif