Error c2504 не определен базовый класс

I checked out a post similar to this but the linkage was different the issue was never resolved. The problem with mine is that for some reason the linker is expecting there to be a definition for the base class, but the base class is just a interface. Below is the error in it’s entirety

c:usersnumerical25desktopintro todirectxgodfilesgxrendermanagergxrendermanagergxrendermanagergxdx.h(2) : error C2504: 'GXRenderer' : base class undefined

Below is the code that shows how the headers link with one another

GXRenderManager.h

#ifndef GXRM
#define GXRM
#include <windows.h>
#include "GXRenderer.h"
#include "GXDX.h"
#include "GXGL.h"

enum GXDEVICE {
    DIRECTX,
    OPENGL
};

class GXRenderManager {
public:
    static int Ignite(GXDEVICE);

private:
    static GXRenderer *renderDevice;

};

#endif

at the top of GxRenderManager, there is GXRenderer , windows, GXDX, GXGL headers. I am assuming by including them all in this document. they all link to one another as if they were all in the same document. correct me if I am wrong cause that’s how a view headers. Moving on…

GXRenderer.h

class GXRenderer {

public:
    virtual void Render() = 0;
    virtual void StartUp() = 0;

};

GXGL.h

class GXGL: public GXRenderer {

public:
    void Render();
    void StartUp();
};

GXDX.h

class GXDX: public GXRenderer {
public:
    void Render();
    void StartUp();
};

GXGL.cpp and GXDX.cpp respectively

#include "GXGL.h"

void GXGL::Render()
{

}

void GXGL::StartUp()
{

}

//...Next document

#include "GXDX.h"


void GXDX::Render()
{

}

void GXDX::StartUp()
{

}

Not sure whats going on. I think its how I am linking the documents, I am not sure.

I checked out a post similar to this but the linkage was different the issue was never resolved. The problem with mine is that for some reason the linker is expecting there to be a definition for the base class, but the base class is just a interface. Below is the error in it’s entirety

c:usersnumerical25desktopintro todirectxgodfilesgxrendermanagergxrendermanagergxrendermanagergxdx.h(2) : error C2504: 'GXRenderer' : base class undefined

Below is the code that shows how the headers link with one another

GXRenderManager.h

#ifndef GXRM
#define GXRM
#include <windows.h>
#include "GXRenderer.h"
#include "GXDX.h"
#include "GXGL.h"

enum GXDEVICE {
    DIRECTX,
    OPENGL
};

class GXRenderManager {
public:
    static int Ignite(GXDEVICE);

private:
    static GXRenderer *renderDevice;

};

#endif

at the top of GxRenderManager, there is GXRenderer , windows, GXDX, GXGL headers. I am assuming by including them all in this document. they all link to one another as if they were all in the same document. correct me if I am wrong cause that’s how a view headers. Moving on…

GXRenderer.h

class GXRenderer {

public:
    virtual void Render() = 0;
    virtual void StartUp() = 0;

};

GXGL.h

class GXGL: public GXRenderer {

public:
    void Render();
    void StartUp();
};

GXDX.h

class GXDX: public GXRenderer {
public:
    void Render();
    void StartUp();
};

GXGL.cpp and GXDX.cpp respectively

#include "GXGL.h"

void GXGL::Render()
{

}

void GXGL::StartUp()
{

}

//...Next document

#include "GXDX.h"


void GXDX::Render()
{

}

void GXDX::StartUp()
{

}

Not sure whats going on. I think its how I am linking the documents, I am not sure.

Just had the same issue. @TheUndeadFish’s answer was a great help, but it took me a while to find the root cause. I’d share below a sample scenario that causes this issue and steps I performed to track it down.

So let’s assume we have three simple classes:

// a.h
#pragma once
#include "b.h"
#include "c.h"

class b;
class c;

class a {
    b* field_b;
    c* field_c;
public:
    a();
};

a depends on b and c.

// b.h
#pragma once
#include "a.h"

class a;

class b {
    a* field_a;
public:
    b();
};

b circularly depends on a (I’m solving that with forward declaration).

// c.h
#pragma once
#include "b.h"

class c : public b {
public:
    c();
};

c derives from b.

The implementation files are very simple as well (only for the sake of simplicity I’m putting all of them in a single block, but keep in mind that those are three separate files):

// a.cpp
#include "a.h"
a::a() { }
// b.cpp
#include "b.h"
b::b() { }
// c.cpp
#include "c.h"
c::c() { }

Now add them to your project, try to compile, and you’ll get something similar to the following error (I’m using Visual Studio):

1>Z:testc.h(6,20): error C2504: ‘b’: base class undefined

So we already know that the problem lies in a fact that in a particular compilation unit compiler sees the child class before it sees the parent class.
How can we prove that? The simplest approach will be to use the message pragma.
I’ve added two messages inside each of the header files, one at the top (before all the include directives) and another one right before the class definition. For example, this is how c.h now looks like:

#pragma once
#pragma message("Top in: " __FILE__)
#include "b.h"

#pragma message("Before class in: " __FILE__)
class c : public b {
public:
    c();
};

Rebuilding the project will show the following output:

Rebuild started…
1>—— Rebuild All started: Project: test, Configuration: Debug x64 ——
1>a.cpp
// redacted..
1>b.cpp
1>Top in: Z:testb.h
1>Top in: Z:testa.h
1>Top in: Z:testc.h
1>Before class in: Z:testc.h
1>Z:testc.h(6,20): error C2504: ‘b’: base class undefined
1>Before class in: Z:testa.h
1>Before class in: Z:testb.h
1>c.cpp
// redacted..
1>Generating Code…
1>Done building project «test.vcxproj» — FAILED.
========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

Please note that b.cpp‘s compilation unit (in bold) fails, and we see where exactly and why: compiler sees the c‘s class definition before it sees b‘s class definition.
A simple fix here will be to move the #include "a.h" directive from b.h into b.cpp. Rebuild the project, and this time the compiler will see the class definitions in a desired order:

Rebuild started…
1>—— Rebuild All started: Project: test, Configuration: Debug x64 ——
1>a.cpp
// redacted
1>b.cpp
1>Top in: Z:testb.h
1>Before class in: Z:testb.h
1>Top in: Z:testa.h
1>Top in: Z:testc.h
1>Before class in: Z:testc.h
1>Before class in: Z:testa.h
1>c.cpp
// redacted
1>Generating Code…
1>test.vcxproj -> test.exe
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========

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[ Script execution time: 0,0576 ]   [ 16 queries used ]   [ Generated: 9.02.23, 12:12 GMT ]  

int main()
{
Mother pot;
pot.sayName();
Daughter kettle;
kettle.sayName();
int pause = 0;
cin >> pause;
}

Mother.h
#ifndef MOTHER_H
#define MOTHER_H

class Mother
{
public:
Mother();
void sayName();

};

#endif
Mother.cpp
#include "stdafx.h"#include<iostream>
#include"Daughter.h"#include"Mother.h"using namespace std;

Mother::Mother()
{
}
void Mother::sayName() {
cout << "What are you doing there?" << endl;

}
Daughter.h
#ifndef DAUGHTER_H
#define DAUGHTER_H

class Daughter:public Mother
{
public:
Daughter();
};
#endif
Daughter.cpp
#include "stdafx.h"#include<iostream>
#include"Daughter.h"#include"Mother.h"using namespace std;

Daughter::Daughter()
{
}

Решение

Другие решения

Других решений пока нет …

Я проверил сообщение, подобное этому, но связь была другой, проблема не была решена. Проблема с моей заключается в том, что по какой-то причине компоновщик ожидает, что там будет определение для базового класса, но базовый класс — это просто интерфейс. Ниже приведена ошибка в целом

c:usersnumerical25desktopintro todirectxgodfilesgxrendermanagergxrendermanagergxrendermanagergxdx.h(2) : error C2504: 'GXRenderer' : base class undefined

Ниже приведен код, который показывает, как заголовки соединяются друг с другом

GXRenderManager.h

#ifndef GXRM
#define GXRM
#include <windows.h>
#include "GXRenderer.h"
#include "GXDX.h"
#include "GXGL.h"

enum GXDEVICE {
    DIRECTX,
    OPENGL
};

class GXRenderManager {
public:
    static int Ignite(GXDEVICE);

private:
    static GXRenderer *renderDevice;

};

#endif

в верхней части GxRenderManager, есть заголовки GXRenderer, windows, GXDX, GXGL. Я предполагаю, включив их всех в этот документ. все они связаны друг с другом, как будто все они находятся в одном документе. исправьте меня, если я ошибаюсь, так как заголовок заголовка. Двигаемся дальше…

GXRenderer.h

class GXRenderer {

public:
    virtual void Render() = 0;
    virtual void StartUp() = 0;

};

GXGL.h

class GXGL: public GXRenderer {

public:
    void Render();
    void StartUp();
};

GXDX.h

class GXDX: public GXRenderer {
public:
    void Render();
    void StartUp();
};

GXGL.cpp и GXDX.cpp соответственно

#include "GXGL.h"

void GXGL::Render()
{

}

void GXGL::StartUp()
{

}

//...Next document

#include "GXDX.h"


void GXDX::Render()
{

}

void GXDX::StartUp()
{

}

Не уверен, что происходит. Я думаю, что как я связываю документы, я не уверен.