Accessing protected method from derived class in a different project (C++) generates linker error

Question

I'm developing in native C++, using visual studio.

---

I have one project which contains infrastructures - base classes which I want to derive classes from in other projects in the same solution. Say I have a base class in the infrastructres project:

file base.h:

class Base
{
      public:
          void Foo();
      protected: 
       void Bar();
};

and in another project, a class derived from A, try to call the method bar:

file derived.h:

class Derived : Base
{
    public:
     void DoSomething();
};

file derived.cpp:

void Derived::DoSomething()
{
 Bar();
}

file main.cpp:

void main()
{
  Derive d;
  d.Foo(); //OK
  d.DoSomething(); // Linker error
}

generates the following linker error:

Error 1 error LNK2001: unresolved external symbol "public: virtual void __thiscall Base::Bar(void)" (?Bar@Base@@UAEXXZ) main.obj CplusplusTestProject

What am I doing wrong?

Answer 1

The simplest possible problem is that you are not linking the library generated in the other project into your own executable.

Answer 2

Make sure your Base::Bar() method has its implementation somewhere. You can just add curly bracers after its definition and rebuild your project.

Answer 3

You need a definition of the Bar member. Add a definition of Bar in the class definition or in a separate base.cpp file.

Answer 4

This is Shelly again. Don't know how to add comments to the answers above. I change the inheritance to public - still not working. Yes, there is an implemenetation to Bar, I just didn't put it in the question. The link error disapears if I change Bar's access level to public - it only apears if Bar is protected. Could it be that the VS linker doesn't add protected and private methods to the symbol table?