Demonstration of a circular doubly linked list

clist.h

#pragma once // or use the #ifndef guard
#include <stddef.h> // for offsetof()

typedef struct cl_head_s {
	struct cl_head_s *prev, *next;
} cl_head_t;

static inline void cl_insert_after(cl_head_t *q, cl_head_t *p)
{ // insert _p_ after _q_; _q_ is in the list
	p->prev = q, p->next = q->next, q->next = p, p->next->prev = p;
}
static inline void cl_push(cl_head_t **head, cl_head_t *p, int push_back)
{
	if (*head) cl_insert_after(*head, p);
	else *head = p, p->prev = p->next = p;
	if (push_back) *head = p;
}
static inline cl_head_t *cl_erase(cl_head_t *p)
{ // erase _p_ in the list; return p->prev, or 0 if p is the only one
	cl_head_t *q = p->prev;
	if (p == q) return 0; // _p_ is the only one in the list
	q->next = p->next, q->next->prev = q;
	return q;
}
static inline cl_head_t *cl_pop(cl_head_t **head, int pop_back)
{
	cl_head_t *p;
	if (*head == 0) return 0;
	p = pop_back? *head : (*head)->next;
	*head = cl_erase(p);
	return p;
}

// Given a pointer to a struct member, get the pointer to the struct
#define cl_container_of(ptr, type, member) ((type*)((char*)(ptr) - offsetof(type, member)))

test.c

#include <stdlib.h> // for malloc()
#include <stdio.h>  // for printf()
#include "clist.h"

typedef struct {
	int x;
	cl_head_t head; // this field forms a double-linked list
} my_elem_t;

static inline my_elem_t *my_elem_create(int x)
{
	my_elem_t *p = (my_elem_t*)malloc(sizeof(*p));
	p->x = x;
	return p;
}

int main(void)
{
	cl_head_t *head = 0;
	cl_push(&head, &my_elem_create(3)->head, 1);
	cl_push(&head, &my_elem_create(4)->head, 1);
	cl_push(&head, &my_elem_create(2)->head, 0);
	cl_push(&head, &my_elem_create(5)->head, 1);
	cl_push(&head, &my_elem_create(1)->head, 0);
	while (head) {
		cl_head_t *p = cl_pop(&head, 1);
		my_elem_t *q = cl_container_of(p, my_elem_t, head);
		printf("out: %d\n", q->x); // in the order of 5, 4, 3, 2, 1
		free(q);
	}
	return 0;
}