哪种方法计算 sockaddr_un 结构的大小是正确的？

Question

The unix domain sockets address structure is defined as:

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

And I see 2 ways of calculating the size, which later on is passed to bind

1. From APUE and 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)

2. The Linux Progamming 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))

Which way is correct? (Maybe both are correct?)

Answer 1

正确的方法是实际使用sizeof (struct sockaddr_un) 。