Tips of Linux C programming

tips.c

//list define
struct list_head {
    struct list_head *next, *prev;
};
#define LIST_HEAD_INIT(name) { &(name), &(name) }

//链表使用者定义：
struct user_t {
    data domain;
    struct list_head node;
};
struct list_head g_user_list = LIST_HEAD_INIT(g_user_list);

//通过node定位user_t:
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#define container_of(ptr, type, member) ({          
    const typeof(((type *)0)->member) * __mptr = (ptr); 
(type *)((char *)__mptr - offsetof(type, member)); })
struct user_t* next = container_of(&(g_user_list.next->node), struct user_t, node);

//高效地分支判断
#define likely(x)       __builtin_expect(!!(x), 1)
#define unlikely(x)     __builtin_expect(!!(x), 0)
long __builtin_expect (long EXP, long C)

//汇编实现的原子操作
__asm__ __volatile__(
                       "   lock       ;n"
                       "   addl %1,%0 ;n"
                       : "=m"  (my_var)   //output
                      : "ir"  (my_int), "m" (my_var)  //input
                      :       //modify  /* no clobber-list */
                      );

//0-length array
struct line {
       int length;
       char content[0];
     };
struct line *thisline = (struct line *)malloc (sizeof (struct line) + content_length);
thisline->length = content_length;