Variable already defined in .obj; What is going on here?

Question

head.h

#pragma once

namespace foo
{
    int bar;

    int funct1();
}

head.cpp

#include \"head.h\"

int foo::funct1()
{
         


        

Answer 1

The header head.h is included in two compilation units head.cpp and main.cpp. So the variable bar is defined twice. You could declare the variable without its definition the following way

#pragma once

namespace foo
{
    extern int bar;

    int funct1();
}

and then define it in some cpp module.