单链表加入节点，而且只是加到末尾，为什么总是不对？
struct link_list
{
struct sock_pipe_map *data;
struct link_list *next;
};

struct sock_pipe_map
{
unsigned int len;
char buf_recv[20];
}

head = (struct link_list *)malloc(sizeof(struct link_list));
head-> data = NULL;
head-> next = NULL;


struct link_list *
add_link(struct link_list *head, struct sock_pipe_map *map)
{
struct link_list *search1;
struct link_list *search2;

search1 = head;

while(search1-> next != NULL)
{
search1 = search1-> next;
}


if((search2 = (struct link_list *)malloc(sizeof(struct link_list)) )== NULL)
{
perror( "malloc error is ");
}

search2-> data = (struct sock_pipe_map *)malloc(sizeof(struct sock_pipe_map));

memset(search2-> data, 0, sizeof(struct sock_pipe_map));
memcpy(search2-> data, map, sizeof(struct sock_pipe_map));


printf( "after memcpy in add_link.\n ");
fflush(stdout);

search1-> next = search2;
search2 -> next = NULL;
return head;

}



[解决办法]
看着没什么问题，只有一点要注意：
没有对struct sock_pipe_map *map这个参数进行检查，如果该参数为NULL
这句可能会有问题的，memcpy(search2-> data, map, sizeof(struct sock_pipe_map))
[解决办法]
首先判断传入的指针是否为NULL
ASSERT(head == NULL);
ASSERT(map == NULL);


[解决办法]
if(head-> data == NULL)晕倒

而且head = search2; 不知道怎么想的，如果head就是专门的指针来就是
head-> next = search2
否则就该传**head