const关键字的internal linkage属性 - gcc

当将const关键字用于声明某个常量时，该标识符自动具备internal linkage属性，即只对相同文件内的函数可见，对其他文件中的函数是不可见的。这可以通过如下的示例程序证明

//const1.cpp

#include <iostream>

using namespace std;

const int a=1;

void funcA()

{

cout<<"cout int A in file const2.cpp have value of "<<a<<endl;

}

// const2.cpp

#include <iostream>

using namespace std;

const int a=2;

extern void funcA();

void funcB()

{

cout<<"cout int A in file const2.cpp have value of "<<a<<endl;

}

int main()

{

funcA();

funcB();

}

编译并执行

g++ const1.cpp const2.cpp

./a.out

输出结果

cout int A in file const2.cpp have value of 1

cout int A in file const2.cpp have value of 2