gcc error, undefined reference

This is a discussion on gcc error, undefined reference within the C Programming forums, part of the General Programming Boards category; EDIT: IGNORE THIS. MODS PLEASE LOCK. PROBLEM SOLVED. READING IS POWER Hello! Getting an undefined reference error. I've got two ...

  1. #1
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    Mar 2011
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    gcc error, undefined reference

    EDIT: IGNORE THIS. MODS PLEASE LOCK. PROBLEM SOLVED. READING IS POWER
    Hello! Getting an undefined reference error. I've got two .c files at the moment.

    pair is a struct with these contents:
    char* word;
    int last_index;
    int list_size;
    char** file_list;
    this is its .c file:
    Code:
    #include "pair.h"
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    Pair pair_construct(char* key, char* file)
    {
      Pair p = malloc(sizeof(struct pair));
      p->word = key;
      p->file_list = calloc(1, sizeof(char*));
      p->file_list[0] = file;
      p->last_index = 1;
      p->list_size = 1;
    }
    
    /* Purpose: free memory associated with a Pair
     * Input: A Pair
     * Output: Freed memory
     */
    void free_pair(Pair p)
    {
      int i;
      for(i=0; i < p->list_size; i++)
        free(p->file_list[i]);
      free(p->word);
      free(p);
    }
    
    /* Purpose: Double the size of a pair's file list
     * to be used when the current list is full.
     * Input: A pair
     * Output: A pair with its file_list doubled in length
     */
    void increase_file_list_length(Pair p)
    {
      p->list_size *= 2;
      p->file_list = realloc(p->file_list, p->list_size*sizeof(char*));
    }
    
    /* Purpose: Add a file to a pair's file list
     * Input: A file name and pair
     * Output: The pair's file list updated
     */
    void add_file(Pair p, char* file)
    {
      if(p->last_index == p->list_size)
        increase_file_list_length(p);
      p->file_list[p->last_index++] = file;
    }
    the second file is a linked list. It utilizes nodes with the following structure:
    Pair p;
    Node next;

    The function below spouts issues:
    Code:
    /* Purpose: Free memory associated with a list
     * Input: Head of a list
     * Output: Freed memory
     */
    void list_free(Node head)
    {
      Node curr = head;
      Node prev = NULL;
      while( curr != NULL )
      {
        prev = curr;
        curr = curr->next;
        pair_free(prev->p);  //undefined reference error
        free(prev);
      }
    }
    prev->p is a pair, and pair_free is a defined function taking a pair as its parameter, but for some reason I'm getting a compile error. Ive used pair functions in my test main in list.c with no problem, but this one is barking at me.

    compiling with "gcc pair.c list.c" gives the following error:

    /tmp/ccnS9s0p.o: In function `list_free':
    list.c.text+0x137): undefined reference to `pair_free'


    Any help is much appreciated

  2. #2
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    That's a linker issue. Since you call pair functions from list code, try reversing the order of files:
    gcc list.c pair.c

    EDIT: nevermind, just saw your edit

  3. #3
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    Location
    Ontario Canada
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    Also... in one file you have free_pair() and in the other you call it as pair_free()

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