c++无法解析的外部符号 "int const bufferSize

无法解析的外部符号 "int const bufferSize

严重性代码说明项目文件行禁止显示状态
错误 LNK2001 无法解析的外部符号 "int const bufferSize" (?bufferSize@@3HB) c8a_demo d:\Users\TT2018\documents\visual studio 2015\Projects\c8a_demo\c8a_demo\demo2.obj 1

在demo2中使用demo1的bufferSize常量时，除了在demo2中设置extern const int bufferSize,

还得在demo1中定义为：extern const int bufferSize(8);

demo2的文件：

#include <iostream>
int bb;
//bb = 22;
extern const int bufferSize;
void foo()
{
    std::cout << "demo2's bb value is : "<<bb << std::endl;

    bb=221;
}
void foo1()
{
    std::cout << "demo2 file is showing: " << bufferSize << std::endl;
}

demo1.cpp

 1 #include <iostream>
 2 int aa(11);
 3 extern int bb;
 4 extern int cc;
 5 extern void foo();
 6 extern void foo1();
 7 extern const int bufferSize(8);//此处应该这样设置。
 8 using namespace std;
 9 int main()
10 {
11 
12     bb = 22;
13 
14     std::cout << "aa value is : " << aa << std::endl;
15 
16     foo();
17 
18     std::cout << "bb's second value is : " << bb << std::endl;
19 
20     for (int i = 0; i != bufferSize; i++)
21 
22         cout << "bufferSize is " << i << endl;
23 
24     foo1();
25 
26     getchar();
27 
28     return 0;
29 
30 }