How to copy a pointer to incomplete type - C++

Question

I'm trying to copy the contents of the pointer myTexture into the pointer texture (a class member), as shown in the code below:

Sprite::Sprite(SDL_Renderer *renderer, SDL_Texture *myTexture) {

    // Initialize texture
    this->texture = myTexture;
}

However, I need to have texture not just point to the same object as myTexture , because I want to be able to modify texture without affecting myTexture as well. I have tried using the copy constructor, but the compiler says that incomplete types are not allowed. I'm not really sure as to how I can create a copy of this object without pointing to the same object.

Thanks in advance for any help.

Answer 1

You cannot call the copy constructor, or generally access any member of an incomplete type. After all, that's what makes it incomplete; you are not supposed to know that the type even supports copying, or anything else.

I'd say just include the whole type rather than just forward-declaring it, and be done with it.

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Edit: I might add that we are talking about an SDL texture type here. This type doesn't look like it even supports copying. It has, for example, "prev" and "next" pointers, and a pointer which seems to point back to a renderer object. Hardly a value class.

It looks like you should reconsider your design as a whole here, and the real question is not about incomplete types but "How to copy SDL_Texture contents."

Answer 2

I think I found a solution. It's not exactly copying the pointer, but what I did is, because I'm using SDL2, I changed the render target to this->texture , and then used SDL_RenderCopy() to put the original texture on the new one. This was the easiest solution I found, unfortunately.