C++ base class undefined

Question

i made class 'Object' and 'Vector', in the each header file. ('Object' is parent class of 'Vector') and made 'Engine.h' header file that include both class header file.

build was successful. but, if i create 'Object.cpp' file which is empty got error. like this 'Vector.h(7,2): error C2504: 'Object': base class undefined'

could you tell me why 'Object.cpp' file occurs this error?

//Engine.h
#pragma once
#include "Object.h"
#include "Vector.h"

namespace Engine
{

}

//Object.h
#pragma once
#include "Engine.h"

namespace Engine
{
    class Object
    {

    };
}

//Vector.h
#pragma once
#include "Engine.h"

namespace Engine
{
    class Vector : public Object
    {

    };
}

#include <iostream>
#include "Engine.h"

int main()
{
    return 0;
}

That's a circular include dependency, which you have to resolve. — Max Langhof, Oct 21 '19 at 15:30
@MaxLanghof I closed. But then I reopened. Both objects don't depend on each other so the solutions will be different — NathanOliver, Oct 21 '19 at 15:32
It doesn't look like either `Vector.h` or `Object.h` need to `#include "Engine.h"`. If `Vector.h` includes `Object.h` directly you resolve your circular include. — François Andrieux, Oct 21 '19 at 15:34
as you said, i removes 'Engine.h' and includes 'Object.h' directly in 'Vector.h'. but same result. :( — ghoflvhxj, Oct 21 '19 at 15:41

Nick Reed · Answer 1 · 2019-10-21T15:31:29.110

2

You've forgotten to #include "Object.h" in your Vector.h file.

It also looks like a lot of your classes rely on one another - that's a bit of a code smell, and it's resulting in compiler errors since you've got circular include statements. If Engine includes Object and Object includes Engine, you can't compile - one of them is always going to be undefined.

edited Oct 21 '19 at 15:31

answered Oct 21 '19 at 15:29

Nick Reed

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Object.h included in Engine.h – ghoflvhxj Oct 21 '19 at 15:30

C++ base class undefined

1 Answers1