Another "Undefined Reference to..."

This is a discussion on Another "Undefined Reference to..." within the C Programming forums, part of the General Programming Boards category; I cannot for the life of my figure this out, probably have been staring at it too long. I have ...

  1. #1
    Registered User carrotcake1029's Avatar
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    Another "Undefined Reference to..."

    I cannot for the life of my figure this out, probably have been staring at it too long. I have been getting this error
    Code:
    main.c:(.text+0x90): undefined reference to `lreceive'
    Here is what I typically use to compile it:
    Code:
    gcc -o a main.c linsock.c -Wall -pthread -pedantic
    I also tried compiling both of them into separate object files and then linking them, but to no avail...
    What I am doing is creating a thread, but the function the thread uses is in another source file. Would that make a difference?

    main.c
    Code:
    pthread_create(&(info.tid), NULL, lreceive, (void *)&info);
    linsock.c
    Code:
    void *lreceive (void *params)
    {
    	struct linfo *info = (struct *linfo)params;
    	int result = 1;
    	char *buffer = malloc(2048 * sizeof(char));
    
    	while (result)
    	{
    		result = recv(info->fsock, buffer, 2048, 0);
    		if (result)
    		{
    			printf("%d bytes received\n");
    		}
    		else
    			break;
    	}
    
    	return NULL;
    }
    Any words of wisdom?

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Your main.c needs to include the header where the function is declared.

  3. #3
    Registered User carrotcake1029's Avatar
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    It does, sorry for not mentioning it.

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by carrotcake1029 View Post
    It does, sorry for not mentioning it.
    Then you don't get that error. See for instance:
    main.c
    Code:
    include "linsock.h"
    
    int main() {
        void *(*f)(void*);
        f = lreceive;
        return 0;
    }
    and linsock.c
    Code:
    #include <stdio.h>
    
    void *lreceive(void *params) {
        printf("Hello from linsock!\n");
        return params;
    }
    (with linsock.h being what you expect) which gives the following errors/warnings:
    Code:
    $ gcc -o a main.c linsock.c -Wall -pedantic
    $

  5. #5
    Registered User carrotcake1029's Avatar
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    I tried that and it compiled for me, but mine still doesn't...

    I will post some trimmed down files for you, because it sounds like I am overlooking something here:

    Sorry for the long post.

    main.c
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    #include "linsock.h"
    
    int main (void)
    {
    	struct linfo info;
    	memset(&info, 0, sizeof(struct linfo));
    	
    	info.host = "google.com";
    	info.port = 80;
    	info.timeout = 5;
    
    	printf("Attempting to connect to %s on port %d\n", info.host, info.port);
    	lconnect(&info);
    	if (info.fsock)
    	{
    		printf("Connected\n");
    		pthread_create(&(info.tid), NULL, lreceive, (void *)&info);
    		pthread_join(info.tid, NULL);
    	}
    	else
    	{
    		printf("%s\n", strerror(errno));
    	}
    
    	close(info.fsock);
    	return 0;
    }
    linsock.c
    Code:
    #include "linsock.h"
    
    void lconnect (struct linfo *info)
    {
        /*
            Yadda Yadda Yadda
        */
    }
    
    void *lreceive (void *params)
    {
    	struct linfo *info = (struct *linfo)params;
    	int result = 1;
    	char *buffer = malloc(2048 * sizeof(char));
    
    	while (result)
    	{
    		result = recv(info->fsock, buffer, 2048, 0);
    		if (result)
    		{
    			printf("%d bytes received\n");
    		}
    		else
    			break;
    	}
    
    	return NULL;
    }
    
    void lresolve (struct linfo *info)
    {
        /*
            Yadda Yadda Yadda
        */
    }
    linsock.h
    Code:
    #ifndef _LINSOCK_H_
    #define _LINSOCK_H_
    
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    
    #include <fcntl.h>
    
    #include <sys/time.h>
    #include <sys/types.h>
    
    #include <sys/types.h>
    #include <sys/socket.h>
    
    #include <pthread.h>
    
    #include <sys/socket.h>
    #include <unistd.h>
    #include <netinet/in.h>
    #include <netdb.h>
    #include <arpa/inet.h>
    
    #include <errno.h>
    
    struct linfo
    {
    	int fsock;
    	char *host;
    	char *ip;
    	short port;
    	int timeout;
    	struct sockaddr_in service;
    	pthread_t tid;
    };
    
    void lresolve (struct linfo *info);
    void lconnect (struct linfo *info);
    void *lreceive (void *params);
    
    #endif

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    After I move the * where it belongs (as in "struct linfo*") on line 12, I get:
    Code:
    $ gcc -o a main.c linsock.c -Wall -lpthread -pedantic
    linsock.c: In function ‘lreceive’:
    linsock.c:21: warning: too few arguments for format
    and that's it.

    Edit: And it runs, says it is trying to get to google.com on port 80, and then dies with unknown error 0.

  7. #7
    Registered User carrotcake1029's Avatar
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    Well crap man, why is my gcc screwing up. I'm using gcc version 4.3.2. I highly doubt the fact that my gcc is about a week out of date makes a difference...

  8. #8
    and the Hat of Guessing tabstop's Avatar
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    Well, I'm running 4.0 so I doubt they broke it since then. Tell you what: can you call the function lreceive? As in just "lreceive(&info)" and see what happens. I doubt you would have fixed a spelling in copy-paste, but I'm starting to run out of ideas.

    Edit: Oh, and something else that shouldn't make a difference: you can try &lreceive in the lpthread_create call and see if that helps. (I don't see how it could, but hey.)
    Last edited by tabstop; 01-28-2009 at 10:02 PM.

  9. #9
    Registered User carrotcake1029's Avatar
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    I cannot. I'm out of ideas too.

  10. #10
    and the Hat of Guessing tabstop's Avatar
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    If you can't call it, then either (a) the header isn't there, somehow, or (b) the function name is mysteriously spelled differently in the header or (c) something else I haven't thought of yet. If you're not getting errors for anything else, then (a) is right out. Edit: And since it's a link error and not a compile error, (b) is right out too.
    Last edited by tabstop; 01-28-2009 at 10:28 PM.

  11. #11
    Registered User carrotcake1029's Avatar
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    Yes, currently that is the only error I am getting. I think I agree with part (c).

  12. #12
    and the Hat of Guessing tabstop's Avatar
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    Alright, well, what's your command line? Are you using a makefile?

  13. #13
    Registered User carrotcake1029's Avatar
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    I've tried both command line and Makefile. I have tried compiling both sources into object files first and then compiling them. Both of them ultimately end up with the same error.

  14. #14
    and the Hat of Guessing tabstop's Avatar
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    Silly idea: put linsock.c first on the command line before main.c (does ld still need functions found before use? I thought they fixed that).

  15. #15
    Registered User carrotcake1029's Avatar
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    Not getting anything new. It could be that I am possibly using a bad compile of gcc. It is doubtful, I know, but I'll compile the newest one tomorrow maybe.

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