Question

I was looking at this question here :
How do I use extern to share variables between source files?
followed the manual . but still I get Linker errors …
Would love to get some help and explanation why it happens..

I have 2 .c files and one header file :

——check.h—-

#ifndef check
#define check

extern int num;

 #endif

—-check.c—-

   #include "check.h"
   #include <stdio.h>



   int func(int x, int y)
   {
int z = x+y;
return z;
   }
   void printnum()
   {
num++;
printf("%d",num);
   }

—-ynnynyny.c—-

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <string.h>
#include "check.h"
#include "check.c"


int num = 10;
int main() 
{ 
printf("num before is : %d\n",num);
printnum();
printf("num now is : %d",num);
getchar();


return 0; 
}

I keep getting these errors :

1>  ynnyny.c
1>  check.c
1>  Generating Code...
1>ynnyny.obj : error LNK2005: _func already defined in check.obj
1>ynnyny.obj : error LNK2005: _printnum already defined in check.obj

I wrote the #ifndef stuff and also the extern declaration, so what Is the problem?

thanks!

Answer 1

don’t include “check.c” in ynnynyny.c