C语言实现双向循环链表

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

struct list_head {
     struct list_head *next, *prev;
};

#define list_entry(ptr, type, member) 
          (type *)( (char *)ptr - ((size_t) &((type *)0)->member))

#define list_for_each(pos, head) 
     for (pos = (head)->next; pos != (head); pos = pos->next)

#define list_for_each_safe(pos, n, head) 
    for (pos = (head)->next, n = pos->next; pos != (head); 
        pos = n, n = pos->next)

static inline void INIT_LIST_HEAD(struct list_head *list)
{
    list->next = list;
    list->prev = list;
}

static inline void list_add_tail(struct list_head *new_node, struct list_head *head)
{
    new_node->next = head;
    new_node->prev = head->prev;
    head->prev->next = new_node;
    head->prev = new_node;
} 

static inline void list_del(struct list_head *entry)
{
     entry->next->prev = entry->prev;
     entry->prev->next = entry->next;
     entry->next = NULL;
     entry->prev = NULL;
}

static inline int list_empty(const struct list_head *head)
{
    return head->next == head;
}

//使用例子
struct stu {
    int num;
    char name[20];
    struct list_head list;
};

int main(void)
{
    struct stu *list_node = NULL;
    struct list_head *pos = NULL,*n = NULL;
    struct stu *pnode = NULL;

    struct stu *head = (struct stu *)malloc(sizeof(struct stu));
    if (head == NULL) {
        printf("file,%s line,%d:malloc error!
",__FILE__,__LINE__);
        exit(1);
    }

    INIT_LIST_HEAD(&head->list);

    list_node = (struct stu *)malloc(sizeof(struct stu));
    if (list_node == NULL) {
        printf("file,%s line,%d:malloc error!
",__FILE__,__LINE__);
        exit(1);
    }

    list_node->num = 0;
    strcpy(list_node->name,"xiaoming");
    list_add_tail(&list_node->list,&head->list);

    list_node = (struct stu *)malloc(sizeof(struct stu));
    if (list_node == NULL) {
        printf("file,%s line,%d:malloc error!
",__FILE__,__LINE__);
        exit(1);
    }

    list_node->num = 1;
    strcpy(list_node->name,"xiaohua");
    list_add_tail(&list_node->list,&head->list);

    if (list_empty(&head->list)) {
        printf("list is empty!
");
    } else {
        list_for_each(pos,&head->list) {
            pnode = list_entry(pos,struct stu,list);
            printf("num:%d,name %s
",pnode->num,pnode->name);
        }
    }

    list_for_each_safe(pos,n,&head->list) {
        list_del(pos);
        pnode = list_entry(pos,struct stu,list);
        printf("num %d has removed from the list!
",pnode->num);
    }   free(pnode);

    free(head);
    return 0;
}