CODEWITHSUNDEEP
csegmentation-faultsizeofcalloc
Pheonix7
Pheonix7

Reputation: 2191

invalid application of ‘sizeof’ and compilation error with struct data

I created a data type which I want to send over a socket. I'm getting a compilation error and a segmentation fault error. The compilation error I get is error: invalid application of ‘sizeof’ to incomplete type ‘struct udp_msg_t’ whereas the segmentation fault happens when I do the memcpy. What am I doing wrong?

Here is some of my code:

This is the struct I'm concerned about which I defined:

typedef struct udp_msg {
    unsigned int udp_eid;
    u_char   udp_prefix;
    unsigned int udp_loc;
} udp_msg_t;

In a method I assign the memory and the values:

void method(){
    udp_msg_t * udp_msg;

    udp_msg = (struct udp_msg_t * )calloc(1, sizeof(struct udp_msg_t));
    udp_msg->udp_eid = eid.u.prefix4.s_addr;
    udp_msg->udp_prefix = eid.prefixlen;
    udp_msg->udp_loc = loc->rloc.rloc.s_addr;

    send_rloc_udp_to_floodlight(udp_msg);
}

And this method actually sends the data over a socket:

int send_rloc_udp_to_floodlight(udp_msg_t message) {
    struct sockaddr_in si_other;
    int s, i, slen = sizeof(si_other);
    char buffer[9];

    if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
        printf("socket");
    }

    memset((char *) &si_other, 0, sizeof(si_other));

    si_other.sin_family = AF_INET;
    si_other.sin_port = htons(8888);

    if (inet_aton("127.0.0.1", &si_other.sin_addr) == 0) {
        fprintf(stderr, "inet_aton() failed\n");
        exit(1);
    }


    memcpy(buffer, (char *) message.udp_eid, sizeof(unsigned int));
    memcpy(&buffer[4], (char *) message.udp_prefix, sizeof(char));
    memcpy(&buffer[5], (char *) message.udp_loc, sizeof(unsigned int));

    //send the message
    if (sendto(s, buffer, strlen(buffer), 0, (struct sockaddr *) &si_other,
            slen) == -1) {
        printf("sendto()");
    }

    close(s);
    return 0;
}

Upvotes: 1

Views: 819

Answers (2)

Pheonix7
Pheonix7

Reputation: 2191

I was not getting the pointer value of the struct field properly. The correct was to do the memcpy is:

memcpy(buffer, (char *) &message.udp_eid, sizeof(unsigned int));

Upvotes: 1

Paul R
Paul R

Reputation: 212959

sizeof(struct udp_msg_t)

is incorrect - it should be either

sizeof(udp_msg_t)

or

sizeof(struct udp_msg)

Ditto for the cast:

(struct udp_msg_t * )

in front of the call to calloc, although this should just be removed, since it's redundant and potentially dangerous.

Upvotes: 2

Related Questions