c++ - unnamed namespace to replace the static symbols

C++ supports a construct that is called unnamed namespace.  with unnamed namespace, one can declare entity local to a file. 

 

 

First let's see an example that uses unnamed namespace.

 

 

/**
* @Name
*   main.cpp
* @Summary
*   Test that unnamed (anonymous) namespace can be used in lieu of static something in C (some local scope construct)
* @NOTE
*  this is a test cpp source file 
*/

#include <iostream>
using namespace std;

namespace {
	void f() { 
		cout << "inside f() " << endl;
	}
}

int main(int argc, char* argv[])  
{
    f();
}

 

 

 

to test that the function only have local visiblity, we can write a new lib.cpp file 

 

 

 

/**
* @Name
*  lib.cpp
* @Comment:
*   use an external symbol, which is f(), there is a local f symbol defined in the main.cpp file
* you are suppose to get the following compile error or similar (depends on the implementation of the compiler)
*   unresolved symbols: 
*     void __cdecl f(void) (?@@YAXXZ)
*   
*/
extern void f();

void g()
{
	f();
};

 

 

as you can see, it has the same semantic of the following 

 

 

 

static void f() 
{
	cout << "inside f()" << endl;
}