Questions about 'extra'!

bigapple · 07-04-2005, 09:07 PM

There are 2 source code file:
def.c

Code:

/*just define the i*/

int i = 3;

print_i.c

Code:

/*display the i*/
#include<stdio.h>

void print_i(void){

            int i;
            printf("The number is %d\n",i);
}

main.c

Code:

#include<stdio.h>
int main(void){
         print_i();
         return 0;
}

As I konw there is something wrong in my code, the varible i is defined in the def.c ,and used in the print_i.c . So I must define the i with 'extern', it means I should use "extern int i" replace the "int i" in the print_i.c. But I haven't make this replacement, the code can run successful.

I want to know is the 'extern' be indispensable to this program?

vharishankar · 07-04-2005, 09:56 PM

By declaring the i locally in the function in print_i.c, you're actually making a local variable distinct from the global one in the other file.

The solution is to include def.c in print_i.c and then not redeclare i in the print_i.c.

I don't think you need to use extern here at all.

vharishankar · 07-04-2005, 09:58 PM

def.c

Code:

/* Just define the i */
int i = 3;

print_i.c

Code:

/*display the i*/
#include<stdio.h>
#include "def.c"

void print_i(void){
            printf("The number is %d\n",i);
}