undefined reference to function that is defined in header file

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2.00/5 (1 vote)

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I am getting undefined reference to sum in 1.c and 2.c. My code:

head.h

Objective-C

#include <stdio.h>
    #ifdef HEAD_H
    #define HEAD_H
    	void sum(int a, int b)
    	{
    		int sum=0;
    		sum=a+b;
    		printf("sum is %d",sum);
    	}
    	
    #endif

1.c

Objective-C

#include "head.h"

   int main()
   {
   sum(1,2);
   callsum();
   }

2.c:

Objective-C

#include "head.h"
    void callsum(void)
    {
    sum(3,4);
    }

I have defined my function and used that header file, still why is this error?

Posted 2-Aug-14 9:45am

Jeevan83

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Comments

Sergey Alexandrovich Kryukov 2-Aug-14 20:44pm

Defining (instead of just declaring) in a header file is possible, but is a big misuse of headers.
You really need to understand what a C compiler does, and what a linker does.
—SA

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OriginalGriff · Accepted Answer · 2014-08-02T10:31:00

Solution 1

Ahem!

#ifdef HEAD_H
#define HEAD_H

you sure?
Did you mean

C++

#ifndef HEAD_H
#define HEAD_H

by any chance?

Posted 2-Aug-14 10:31am

OriginalGriff

Comments

Philippe Mori 2-Aug-14 23:18pm

Well spotted... even though there are many other problem as indicated by SA.

Jeevan83 3-Aug-14 3:45am

Oh am I using #ifdef ? What kind of a fool am I? Sorry for wasting everyone's valuable time and mine too. Please spare this girl for the last time! Too ashamed to keep my question here. Only God can save me! How can I delete it?

OriginalGriff 3-Aug-14 5:08am

Easy mistake to make - I always end up reading when I *meant* to write instead of what I *did*.
I wouldn't worry about deleting the question - it might help someone else in the same position, and it's considered rude to delete them anyway! :laugh:

Jeevan83 3-Aug-14 13:17pm

Hey don't laugh it's hard to manage kitchen and computer sigh!