Thread: undefined reference to `getnumber' collect2.exe: error: ld returned 1 exit status

Hi All,

How do I create a project using multiple source files?

I understand the concept of including header files but I don't really know how to combine other source files.

Here is what I tried

main.c

Code:

#include<stdio.h>
#include"other.h"
 
int main (void)
{
    printf("%d\n", getnumber());
 
    return 0;
}

other.h

Code:

#include "other.h"
 
int getfavoritenumber(void)
{
    return 3;
}

other.c

Code:

#ifndef _OTHER_H_
#define _OTHER_H_
 
int getnumber(void);
 
#endif

compiler gives error

undefined reference to `getnumber'
collect2.exe: error: ld returned 1 exit status

What's wrong with files ?

Well... for a start you haven't implemented getnumber() in other.c (assuming that you have just got the filenames back to front on here but they're right on your computer). You've implemented a function called getfavouritenumber() but not getnumber()

I have replaced this file

other.h

Code:

#include "other.h"
int getnumber(void)
{
    return 3;
}

error is same

Ok, I think you have other.h and other.c mixed up.

other.c should contain

Code:

#include "other.h"
int getnumber(void)
{
    return 3;
}

other.h should contain

Code:

#ifndef _OTHER_H_
#define _OTHER_H_
  
int getnumber(void);
  
#endif

i.e. the implementation of the function goes into the .c file (normally, and in this case certainly)

Then compile with something like gcc -Wall main.c other.c (depending on what compiler you're using)

Originally Posted by Hodor

Ok, I think you have other.h and other.c mixed up.



i.e. the implementation of the function goes into the .c file (normally, and in this case certainly)

Then compile with something like gcc -Wall main.c other.c (depending on what compiler you're using)

Here is complete file with path

C:\Users\Vij\Desktop\other.c

Code:

#include "other.h"
int getnumber(void)
{
   return 3;
}

C:\Users\Vij\Desktop\other.h

Code:

#ifndef _OTHER_H_
#define _OTHER_H_
  
int getnumber(void);
  
#endif

C:\Users\Vij\Desktop\main.c

Code:

#include<stdio.h>
#include"other.h"
 
int main (void)
{
    printf("%d\n", getnumber());
 
    return 0;
}

Then compile with something like gcc -Wall main.c other.c

C:\Users\Vij\AppData\Local\Temp\cc8OxdX2.o:main.c.text+0xf): undefined reference to `getnumber'
collect2.exe: error: ld returned 1 exit status

Also, based on your path names you're using Windows. I know mingw and forks, and cygwin are popular but if you just need to compiler programs and not necessarily create Windows .exe files then I find that Windows Subsystem for Linux (WSL) is pretty good. The downsides are you need Windows 10 and you'll need to learn a few linux commands (but not many to get started). So, if you have Windows 10 and don't need Windows executables (i.e. just being able to compile and run programs is enough) then personally I'd use WSL instead of mingw or cygwin. The upside is that you get to learn Linux and don't have to dualboot etc etc. At least read about WSL if you have Windows 10.

Edit: I'm not suggesting that mingw etc and cygwin are terrible (they're not and they serve the community well); I'm just suggesting that *I* would use WSL instead of those if I had a choice

Originally Posted by Hodor

Edit: I'm not suggesting that mingw etc and cygwin are terrible (they're not and they serve the community well); I'm just suggesting that *I* would use WSL instead of those if I had a choice

Thank! Hodor

Finally I got working. yes I am working on windows 10

gcc -o main main.c other.c

C:\Users\Vij\Desktop>main
3

Originally Posted by abhi143

Thank! Hodor

Finally I got working. yes I am working on windows 10

gcc -o main main.c other.c

C:\Users\Vij\Desktop>main
3

Great

The -o is just to give the output file a name (other than a.out) so maybe that's a mingw requirement (it's not necessary on Linux). I'd definitely add -Wall to your command line, though, because you want compiler warnings turned on.

gcc -Wall -o main main.c other.c

Originally Posted by Hodor

Great

The -o is just to give the output file a name (other than a.out) so maybe that's a mingw requirement (it's not necessary on Linux). I'd definitely add -Wall to your command line, though, because you want compiler warnings turned on.

gcc -Wall -o main main.c other.c

gcc -Wall -o main main.c other.c

yes this command also work on windows

Originally Posted by Hodor

Great

The -o is just to give the output file a name (other than a.out) so maybe that's a mingw requirement (it's not necessary on Linux). I'd definitely add -Wall to your command line, though, because you want

Hi Hodor

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