Thread: Linkage error

  1. #1
    Registered User
    Join Date
    Jun 2021
    Posts
    1

    Linkage error

    Hello,

    I have used C in the past. but have gotten EXTREMELY rusty at it. I currently have four files in my directory (ex.c, ex.h, menu.c, and menu.h).

    menu.h is this:
    Code:
    #ifndef MENU_H
    #define MENU_H
    
    #include <stdio.h>
    
    void print_header(void);
    int get_choice(void);
    
    #endif
    menu.c is this:
    Code:
    #include "menu.h"
    
    void print_header(void) {
        printf("--- Chapter 1 Examples ---\n");
    }
    ex.h is this:
    Code:
    #include <stdio.h>
    
    void ex_1(void);
    and ex.c is this:
    Code:
    #include "ex.h"
    #include "menu.h"
    
    int main() {
        print_header();
        return 0;
    }
    Currently, I am trying to run print_header in ex.c to make sure everything works but I am getting a linkage error.
    Code:
    ex.c:(.text+0x9): undefined reference to `print_header' 
    collect2: error: ld returned 1 exit status
    Can someone refresh why this is happening and how to fix it? Thank you

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    Location
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    Posts
    38,660
    You need to compile everything
    gcc menu.c ex.c
    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.

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