Question

I have a library that is abstracted and basically looks like this:

A.h

namespace N {
    class A
}

B.h

#pragma once
#ifndef B
#define B
#include "A.h" 
namespace N {
    class B: Public A
}
#endif

And the library is referenced in the CMakelists.txt like this:

global_add_library(libN A.cpp B.cpp)
target_link_libraries(libN someLibraries)

Now I have the main file which looks like this:

#include <libN/A.h>
#include <libN/B.h>

N::A a* = new A();
N::B b* = new B();

And its CMakelists.txt looks like this:

global_add_exectubale(application somemainccpfiles.cpp)
target_link_libraries(application libN)

What i am getting is an error saying

error: ISO C++ forbids deceleration of 'B' with no type.

So i am thinking that the B.h file isnt included properly? But why when the deceleration of A is just fine?

Any ideas?

EDIT: So I found out what the original problem was, the combination of the pragma once and the ifndef meant it wasn’t compiling properly. When I removed the pragma once it was fixed. But now the question is why is that? Shouldn’t it have worked even with both?

Answer 1

#include "A.h" 
namespace N {
    class B: Public A
}

Your included “A.h” but in other file it was “libN/A.h”