c - 哪种计算 sockaddr_un 结构大小的方法是正确的？

Question

unix域套接字地址结构定义为:

struct sockaddr_un {
    sa_family_t sun_family; /* AF_UNIX */
    char sun_path[108]; /* pathname */
};

我看到了两种计算大小的方法，稍后将其传递给 bind

来自 APUE 和 http://beej.us/guide/bgipc/html/multi/unixsock.html

//beej's guide
struct sockaddr_un local;
int len;

len = strlen(local.sun_path) + sizeof(local.sun_family);
bind(s, (struct sockaddr *)&local, len);

//APUE
struct sockaddr_un un;
size = offsetof(struct sockaddr_un, sun_path) + strlen(un.sun_path);
bind(fd, (struct sockaddr *)&un, size)

Linux 编程接口(interface)

const char *SOCKNAME = "/tmp/mysock";
struct sockaddr_un addr;
addr.sun_family = AF_UNIX; /* UNIX domain address */
strncpy(addr.sun_path, SOCKNAME, sizeof(addr.sun_path) - 1);
bind(sfd, (struct sockaddr *) &addr, sizeof(struct sockaddr_un))

哪种方式是正确的？ (也许两者都是正确的？)

Answer 1

正确的方法是使用sizeof (struct sockaddr_un)实际上。