c - 使用共享内存将 addrinfo 结构从子级传递到父级

Question

我想使用如下共享内存将 getaddrinfo 结构 (*res) 的输出传递到父(从子)进程

pid = fork();
if (pid == 0)
{
    .....
    iStatus = getaddrinfo(argv[1], NULL, &hints, &servinfoC);
    ...
    shmid = shmget(GETADDR_SHM_KEY, SHMSZ, IPC_CREAT | 0666);
    ....
    shmC = shmat(shmid, (void*)NULL, 0));
    memcpy(shmC, servinfoC, sizeof(struct addrinfo));
    freeaddrinfo (servinfoC);
}
else
{
    struct addrinfo *servinfoP;
    while ((pid = waitpid (pid, &status, WUNTRACED | WCONTINUED)) > 0)
    shmid = shmget(GETADDR_SHM_KEY, SHMSZ, 0666 | IPC_CREAT);
    shmP = shmat(shmid, (void*)NULL, 0));

    /*HELP Copy shmP to servinfoP struct*/

}

我试过 memcpy 但它没有帮助，因为 addrinfo 需要内存分配。

预先感谢您的时间和帮助

问候马诺杰

Answer 1

这是行不通的。 addrinfo 结构包含指向其他内存区域的指针，在其之上是一个结果链表。如果你想通过共享内存传递它，你需要将它展平。

例如:

struct addrinfo_flat
{
    int ai_family;
    int ai_socktype;
    int ai_protocol;
    struct sockaddr_storage ai_addr;
    socklen_t ai_addrlen;
};

struct addrinfo_flags *addrs = (struct addrinfo_flat*)shmC;
addrs->ai_family = ai->ai_family;
addrs->ai_socktype = ai->ai_socktype;
addrs->ai_protocol = ai->ai_protocol;
memcpy(&addrs->ai_addr, ai->ai_addr, ai->ai_addrlen);
addrs->ai_addrlen = ai->ai_addrlen;

(留下多个结果作为练习)