Question

So this is what I have:

//graphics.hpp
#include guard

extern camera_c default_camera;

namespace graphics {
    camera_c &camera = default_camera;
};

#endif


//graphics.cpp

camera_c default_camera(ctor stuff);

---

//main.cpp

#include <graphics.hpp>

int main() {
    do stuff with graphics::camera;
}

and this gives me

main.o: multiple definition of graphics::camera
graphics.o: first defined here

I’ve also tried doing

camera_c &&camera = camera_c(ctor stuff);

And that gives me the same error, but from main.cpp and graphics.cpp

So my question is

Is there some feasible way to have a reference to a class in that namespace? Or should I just use a pointer? Ideally it should be a reference, but that might not be possible.

Answer 1

You’re misunderstanding the error.

The error is telling you that main.cpp and graphics.cpp both included graphics.hpp, which violates the One Definition Rule.

Make that variable extern as well:

namespace graphics {
    extern camera_c &camera;
};

And define it in one source file only.

namespace graphics {
    camera_c &camera = default_camera;
};