未定义的'stu1' 结构体的定义，有个小问题,帮忙看看
主程序
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struct student stu1;
int main(int argc, char* argv[])
{
getStudentName();
printf( "%d ",stu1.no);
getch();
return 0;
}
-------------------------------

a.h
-------------------------------
struct student{
int no;
char *name;
};

void getStudentName(void);
-------------------------------

a.c
-------------------------------
#include "a.h "
//extern struct student stu1;

void getStudentName(void){
stu1.id=5;
}
-------------------------------

报错：a.c里的 stu1.id=5;
[C++ Error] a.c(5): E2451 Undefined symbol 'stu1 '
未定义的 'stu1 '，为什么？


[解决办法]
#include "a.h "
[解决办法]
重复包含了 "a.h "

用条件编译

#ifndef _A_H_H
#include "a.h "
#endif
[解决办法]
extern struct student stu1; 不能删
[解决办法]
a.h
-------------------------------
#ifndef _A_H_H
#define _A_H_H

struct student{
int no;
char *name;
};

void getStudentName(void);

#endif
-------------------------------

a.c
-------------------------------
#include "a.h "

struct student stu1;

void getStudentName(void){
stu1.id=5;
}
-------------------------------


主程序
-------------------------------

#include "a.h "

extern struct student stu1;

int main(int argc, char* argv[])
{
getStudentName();
printf( "%d ",stu1.no);
getch();
return 0;
}
-------------------------------