strange core dump at memcpy

    int connect_host(s_host_t * h, int recv_sec, int send_sec)
{
    int sock = -1;
    int ret;
    int select_ret;
    int res;
    socklen_t res_size = sizeof res;
    struct sockaddr_in channel;
    struct hostent host;
    struct timeval recv_timeout;
    struct timeval send_timeout;
    fd_set wset;

    if (FAIL_CHECK(!gethostname_my(h->addr, &host)))
    {
        gko_log(WARNING, "gethostbyname %s error", h->addr);
        ret = -1;
        goto CONNECT_END;
    }
    sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (FAIL_CHECK(sock < 0))
    {
        gko_log(WARNING, "get socket error");
        ret = -1;
        goto CONNECT_END;
    }

    recv_timeout.tv_usec = 0;
    recv_timeout.tv_sec = recv_sec ? recv_sec : RCV_TIMEOUT;
    send_timeout.tv_usec = 0;
    send_timeout.tv_sec = send_sec ? send_sec : SND_TIMEOUT;

    memset(&channel, 0, sizeof(channel));
    channel.sin_family = AF_INET;
    memcpy(&channel.sin_addr.s_addr, host.h_addr, host.h_length);
    channel.sin_port = htons(h->port);

    /** set the connect non-blocking then blocking for add timeout on connect **/
    if (FAIL_CHECK(setnonblock(sock) < 0))
    {
        gko_log(WARNING, "set socket non-blocking error");
        ret = -1;
        goto CONNECT_END;
    }

    /** connect and send the msg **/
    if (FAIL_CHECK(connect(sock, (struct sockaddr *) &channel, sizeof(channel)) &&
            errno != EINPROGRESS))
    {
        gko_log(WARNING, "connect error");
        ret = HOST_DOWN_FAIL;
        goto CONNECT_END;
    }

    /** Wait for write bit to be set **/
    ///
    FD_ZERO(&wset);
    FD_SET(sock, &wset);
    select_ret = select(sock + 1, 0, &wset, 0, &send_timeout);
    if (select_ret < 0)
    {
        gko_log(FATAL, "select error on connect");
        ret = HOST_DOWN_FAIL;
        goto CONNECT_END;
    }
    if (!select_ret)
    {开发者_运维百科
        gko_log(FATAL, "connect timeout on connect");
        ret = HOST_DOWN_FAIL;
        goto CONNECT_END;
    }

    /**
     * check if connection is RESETed, maybe this is the
     * best way to do that
     * SEE: http://cr.yp.to/docs/connect.html
     **/
    (void) getsockopt(sock, SOL_SOCKET, SO_ERROR, &res, &res_size);
    if (CONNECT_DEST_DOWN(res))
    {
        gko_log(NOTICE, "dest is down SO_ERROR: %d", res);
        ret = HOST_DOWN_FAIL;
        goto CONNECT_END;
    }

    ///gko_log(WARNING, "selected %d ret %d, time %d", sock, select_ret, send_timeout.tv_sec);
    /** set back blocking **/
    if (FAIL_CHECK(setblock(sock) < 0))
    {
        gko_log(WARNING, "set socket non-blocking error");
        ret = -1;
        goto CONNECT_END;
    }

    /** set recv & send timeout **/
    if (FAIL_CHECK(setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (char *) &recv_timeout,
                    sizeof(struct timeval))))
    {
        gko_log(WARNING, "setsockopt SO_RCVTIMEO error");
        ret = -1;
        goto CONNECT_END;
    }
    if (FAIL_CHECK(setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (char *) &send_timeout,
                    sizeof(struct timeval))))
    {
        gko_log(WARNING, "setsockopt SO_SNDTIMEO error");
        ret = -1;
        goto CONNECT_END;
    }

    ret = sock;

    CONNECT_END:
    ///
    if (ret < 0 && sock >= 0)
    {
        close_socket(sock);
    }
    return ret;
}

gethostname_my：

struct hostent * gethostname_my(const char *host, struct hostent * ret)
{
    struct hostent * tmp;
    if (!ret)
    {
        gko_log(FATAL, "Null buf passed to gethostname_my error");
        return (struct hostent *) NULL;
    }

    pthread_mutex_lock(&g_netdb_mutex);
    tmp = gethostbyname(host);
    if (tmp)
    {
        memcpy(ret, tmp, sizeof(struct hostent));
    }
    else
    {
        gko_log(WARNING, "resolve %s failed", host);
        ret = NULL;
    }
    pthread_mutex_unlock(&g_netdb_mutex);

    return ret;
}

the func above cored at "memcpy(&channel.sin_addr.s_addr, host.h_addr, host.h_length);" several times. how can this possible??? gdb says it was terminated by signal 11

#0  0x000000302af71900 in memcpy () from /lib64/tls/libc.so.6
(gdb) bt
#0  0x000000302af71900 in memcpy () from /lib64/tls/libc.so.6
#1  0x000000000040c42f in connect_host (h=0x2cd13ee060, recv_sec=2, send_sec=2) at socket.cpp:121
#2  0x0000000000409f65 in sendcmd (h=0x2cd13ee060, cmd=0x2a9bcf4fb0 "DELE\t127.0.0.1\t59968", recv_sec=2, send_sec=2) at gingko_base.cpp:643
#3  0x000000000040685e in quit_job_s (uri=0x2cd13ed170, fd=1015) at gingko_common.h:550
#4  0x0000000000403e48 in conn_send_data (fd=1015, str=0x2cd13ed170, len=8) at async_conn.cpp:281
#5  0x0000000000404045 in conn_tcp_server_on_data (fd=1015, ev=2, arg=0x1d51a00) at async_conn.cpp:358
#6  0x000000000040f537 in event_base_loop (base=0x7b1ab0, flags=0) at event.c:392
#7  0x00000000004034cf in thread_worker_init (arg=0x7b1a00) at async_threads.cpp:84
#8  0x000000302b80610a in start_thread () from /lib64/tls/libpthread.so.0
#9  0x000000302afc6003 in clone () from /lib64/tls/libc.so.6
#10 0x0000000000000000 in ?? ()
(gdb) f 1
#1  0x000000000040c42f in connect_host (h=0x2cd13ee060, recv_sec=2, send_sec=2) at socket.cpp:121
121         memcpy(&channel.sin_addr.s_addr, host.h_addr, host.h_length);
(gdb) p host
$1 = {h_name = 0x2ccd100d08 "127.0.0.1", h_aliases = 0x2ccd100d00, h_addrtype = 2, h_length = 4, h_addr_list = 0x2ccd100cf0}
(gdb) p &channel.sin_addr.s_addr
$2 = (in_addr_t *) 0x2a9bcf4f04
(gdb) p channel
$3 = {sin_family = 2, sin_port = 0, sin_addr = {s_addr = 0}, sin_zero = "\000\000\000\000\000\000\000"}
(gdb) p host.h_addr_list[0]
$5 = 0x2ccd100ce0 "\177"
(gdb) p host.h_addr_list[0][0]
$6 = 127 '\177'
(gdb) p host.h_addr_list[0][1]
$7 = 0 '\0'
(gdb) p host.h_addr_list[0][2]
$8 = 0 '\0'
(gdb) p host.h_addr_list[0][3]
$9 = 1 '\001'

---

You are calling to gethostname_my, but have not provided its definition.

I'd say that it calls gethostname and return a copy of the hostent struct. But note that h_addr is a macro that expands to h_addr_list[0], so if the gethostname_my function does not copy the list appropriately, it will not work.

CLARIFICATION: gethostname is not reentrant. It uses a global static chunk of memory to return the data. That data contains the hostent struct and a variable amount of aliases and addresses. They are usually, but not necessarily next to this struct.

If you are trying to make a re-entrant version of this function, then you should:

• Lock, with a mutex or similar, every use of this function (hard to do if you use third party libraries that may call it without you knowing).
• Copy the hostent struct and all the aliases and addresses pointed to by this struct.

But why should you bother when you have the (not so) new and improved getaddrinfo function? This is reentrant and just does The Tight Thing (tm).

---

h_addr is char* as seen below holding the ip address of the host . So the length could be anything up to 15 bytes.

struct hostent
{
    char *h_name;           /* Official name of host.  */
    char **h_aliases;       /* Alias list.  */
    int h_addrtype;     /* Host address type.  */
    int h_length;           /* Length of address.  */
    char **h_addr_list;     /* List of addresses from name server.  */
    #define h_addr  h_addr_list[0]  /* Address, for backward compatibility.  */
};

Whereas s_addr is 4 bytes. Most probably h_addr length exceeds 4 bytes and lead to core dump

---

the field

 s_addr

is a long (I guess 8 bytes?)

You are copying

 host.h_length 

bytes. What is the value of h_length in the cases that it fails?