Thread: confusion on the difference between external and static

> #include "functionimporttest.c"
Most of your confusion comes from this.

Including .c files is 99% the wrong thing to be doing.

You need
#include "functionimporttest.h"

Where the .h file contains

Code:

#ifndef FUNCTIONIMPORTTEST_H
#define FUNCTIONIMPORTTEST_H

extern int glob;

void add(int a, int b);

#endif

functionimporttest.c also needs
#include "functionimporttest.h"