如何在 Allegro 位图上使用智能指针？

Question

I've decided I'm tired of deciding which classes are responsible for deleting which bitmaps. I've tried to rewrite my code to use smart pointers with a custom deleter al_destroy_bitmap

My code is pretty simple.

shared_ptr<ALLEGRO_BITMAP> test = make_shared<ALLEGRO_BITMAP>(al_load_bitmap("hello.png"), al_destroy_bitmap);

I'm getting quite a few errors which I just can't seem to work around.

error C2079: 'std::_Get_align<ALLEGRO_BITMAP>::Elt2' uses undefined struct 'ALLEGRO_BITMAP'
error C2079: 'std::_Get_align<ALLEGRO_BITMAP>::Elt0' uses undefined struct 'ALLEGRO_BITMAP'
error C2027: use of undefined type 'ALLEGRO_BITMAP'
error C2027: use of undefined type 'ALLEGRO_BITMAP'

Other solutions to solve my problem would be creating a Bitmap class to wrap all of the Allegro stuff, but that seems ugly, and I don't think I should have to do that. Plus I already use other allegro functions everywhere, and then I would want to then write those same types of classes for ALLEGRO_SAMPLE and ALLEGRO_FONT . I really don't feel like doing that.

How can I use smart pointers with Allegro bitmaps?

Edit: Perhaps to give non-Allegro coders a feel for how ALLEGRO_BITMAPs work, I'll post a little code below

ALLEGRO_BITMAP *test = al_load_bitmap("hello.png") // This works
ALLEGRO_BITMAP test1; // This fails with error C2079 undefined struct ALLEGRO_BITMAP. I expect this here.

Answer 1

Like this:

std::shared_ptr<ALLEGRO_BITMAP> test(al_load_bitmap("hello.png"), al_destroy_bitmap);

Remember: make_shared and make_unique call new , you don't want that here.

Also make_x<T> constructs an object of type T , passing the given arguments to T 's constructor. But al_load_bitmap returns a pointer to a fully constructed object so you don't want to call any constructor (except the smart pointer constructor).