C++ Simple circular reference and forward declaration issue

Question

I get this error:

error C3646: 'bar': unknown override specifier

when trying to compile this very simple C++ code in Visual Studio 2015:

main.cpp:

#include "Foo.h"

int main ()
{
    return 0;
}

Foo.h:

#pragma once

#include "Bar.h"

class Foo
{
public:
    Foo();

    Bar bar;
};

Bar.h:

#pragma once

#include "Foo.h"

class Bar
{
public:
    Bar();
};

I get there is a circular reference because each .h includes the other, and the solution should be using forward declarations, but they don't seem to work, could someone explain why? I found similar problems here, and the solutions is always the same, I think I'm missing something :)

Answer 1

The circular reference is entirely of your own making, and you can safely remove it by removing the #include "Foo.h" from Bar.h:

#pragma once

//#include "Foo.h"  <---- not necessary, Bar does not depend on Foo

class Bar
{
public:
    Bar();
};

You do not need a forward declaration of Bar inside Foo.h. A more general case would be if Foo and Bar were mutually dependent on each other, that would require forward declarations.