C语言学习

lifetime.c

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

//extern int step;  // has no effect

static void hide_exobj()
{
    int exobj;
    printf("exobj(hide_exobj) address: %p\n",
        &exobj);
}

int main(int argc, char *argv[])
{
    extern int exobj;

    printf("exobj(main) address: %p\n",
        &exobj);
    hide_exobj();

    //printf("step is %d\n", step);

    printf("original exobj is %d\n",
        exobj);
    printf("add exobj by 1\n");
    exobj++;
    printf("exobj becomes %d\n",
        exobj);

    inc_exobj();
    dec_exobj();

    return 0;
}

otherfile.h

#ifndef OTHERFILE_H_
#define OTHERFILE_H_

extern int exobj;
extern void inc_exobj();
extern void dec_exobj();

#endif

otherfile1.c

#include <stdio.h>

int exobj = 0;
//static int exobj;  // error
static int step = 1;
extern int step;  // has no effect

static void step_exobj()
{
    exobj += step;
}

void inc_exobj()
{
    step_exobj();
    printf("increased exobj: %d\n",
        exobj);
}

otherfile2.c

#include <stdio.h>

extern int exobj;
static int step = -1; 

static void step_exobj()
{
    exobj += step;
}

void dec_exobj()
{
    step_exobj();
    printf("decreaseed exobj: %d\n",
        exobj);
}