[tsimionescu]

Most typically when using arenas, you don't want to pay the cost of de-allocation at all while the arena is still alive. So, you actually have to "fight" unique_ptr, since you don't want it to call any kind of delete() or destructor, and you essentially get nothing in return.

If you use a bare pointer instead, not only do you get the same guarantees, but now if you need to modify the code to actually share that object, there's no need to modify any references from unique_ptr to shared_ptr.

[chlorion]

Yeah! That's what I meant when I said arenas solve a different problem! I don't think I mentioned using unique_ptr with the arena and I didn't mean to suggest that if I did. My point was that arenas are not a replacement for unique_ptr at all, and instead solve a different problem where allocations don't have a simple and deterministic lifetime.

With an arena ideally you can just pass out actual references (T&) to callers instead of pointers!

[tsimionescu]

I believe that there are certain situations where one may choose between scope-based memory management and arena-based. Even for the example of the rendering code of a frame, instead of allocating inside an arena, you could choose to allocate an object graph owned by some frame-level object, that is de-allocated once the frame is rendered.