Unexpected Error

This is a discussion on Unexpected Error within the Linux Programming forums, part of the Platform Specific Boards category; A simple client with no errors in code gave me these errors? Any answers? gcc client.c Undefined first referenced symbol ...

  1. #1
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    Unexpected Error

    A simple client with no errors in code gave me these errors? Any answers?

    gcc client.c
    Undefined first referenced
    symbol in file
    gethostbyname /var/tmp//ccJVrXcl.o
    socket /var/tmp//ccJVrXcl.o
    connect /var/tmp//ccJVrXcl.o
    ld: fatal: Symbol referencing errors. No output written to a.out
    collect2: ld returned 1 exit status

    Code:
    #include <stdio.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <netdb.h>
     
    void error(char *msg)
    {
        perror(msg);
        exit(0);
    }
     
    int main(int argc, char *argv[])
    {
        int sockfd, portno, n;
        struct sockaddr_in serv_addr;
        struct hostent *server;
     
        char buffer[256];
        if (argc < 3) {
           fprintf(stderr,"usage %s hostname port\n", argv[0]);
           exit(0);
        }
        portno = atoi(argv[2]);
        sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (sockfd < 0)
            error("ERROR opening socket");
        server = gethostbyname(argv[1]);
        if (server == NULL) {
            fprintf(stderr,"ERROR, no such host\n");
            exit(0);
        }
     
        bzero((char *) &serv_addr, sizeof(serv_addr));
        serv_addr.sin_family = AF_INET;
        bcopy((char *)server->h_addr,
             (char *)&serv_addr.sin_addr.s_addr,
             server->h_length);
        serv_addr.sin_port = htons(portno);
     
        if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr))== -1){
            error("ERROR connecting");
            exit(0);
            }
        else
        printf("Please enter the message: \n");
        bzero(buffer,256);
        fgets(buffer,255,stdin);
        n = write(sockfd,buffer,strlen(buffer));
        if (n < 0)
             error("ERROR writing to socket");
        bzero(buffer,256);
        n = read(sockfd,buffer,255);
        if (n < 0)
             error("ERROR reading from socket");
        printf("%s\n",buffer);
        return 0;
    }
    Last edited by Vendicate; 04-03-2006 at 08:57 PM.

  2. #2
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    first of all fix the includes

    linker.c: In function `error':
    linker.c:10: warning: implicit declaration of function `exit'
    linker.c: In function `main':
    linker.c:24: warning: implicit declaration of function `atoi'
    linker.c:34: warning: implicit declaration of function `bzero'
    linker.c:36: warning: implicit declaration of function `bcopy'
    linker.c:41: warning: implicit declaration of function `size'
    linker.c:49: warning: implicit declaration of function `write'
    linker.c:49: warning: implicit declaration of function `strlen'
    linker.c:53: warning: implicit declaration of function `read'
    linker.c:58:2: warning: no newline at end of file
    /tmp/ccFCV3x1.o: In function `main':
    linker.c.text+0x147): undefined reference to `size'
    collect2: ld returned 1 exit status
    Size is not defined might be a typo for sizeof.

  3. #3
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    What needs to be fixed in the includes? That is the initial reason why i posted this, i knew there was a problem with the include just by running:

    gcc client.c -E

    So any answers?
    Last edited by Vendicate; 04-03-2006 at 09:41 PM.

  4. #4
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    Anyone?

  5. #5
    ATH0 quzah's Avatar
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    I'll assume you know what a man page is. Ok, so how about looking up each function to see what header it requires, eh?

    man 3 exit


    Quzah.
    Hope is the first step on the road to disappointment.

  6. #6
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    I have added #include <stdlib.h> and have MANed all my functions, they all have the includes needed, but I still get the same error???

  7. #7
    and the hat of wrongness Salem's Avatar
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    > gcc client.c
    Code:
    gcc client.c -lsocket
    You need to specify one (or more) additional libraries to resolve the network API calls.
    I'm not at a linux machine right now to remember whether that's the right name for the library.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  8. #8
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    Code:
    gcc client.c -lsocket
    Undefined                       first referenced
     symbol                             in file
    gethostbyname                       /var/tmp//ccQMAIhu.o  (symbol belongs to implicit dependency /usr/lib/libnsl.so.1)
    ld: fatal: Symbol referencing errors. No output written to a.out
    collect2: ld returned 1 exit status
    This code is taken directly from http://www.cs.rpi.edu/courses/sysprog/sockets/client.c

    should work...

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