구조체 안의 구조체의 자료구조 질문입니다

typedef struct _user
{
        char u_name[20];
        struct _user *u_next;
}user;
user *u_head, *u_tail;
 
typedef struct _channel
{
        int user_count;
        char channel_name[20];
        struct _channel *c_next;
        struct _user *user;
}channel;
channel *c_head, *c_tail;
 
void init_user(void)
{
        u_head=(user*)malloc(sizeof(user));
        u_tail=(user*)malloc(sizeof(user));
        u_head->u_next=u_tail;
        u_tail->u_next=u_tail;
}
void init_channel(void)
{
        c_head=(channel*)malloc(sizeof(channel));
        c_tail=(channel*)malloc(sizeof(channel));
        c_head->c_next=c_tail;
        c_tail->c_next=c_tail;
}