[riku_iki]

I am not sure I understand moving GC concern. Arena content would not be controlled by GC, otherwise it defeats the purpose of Arena.

[tpolzer]

A moving GC would make it simple to move any remaining live objects back under normal GC control once the arena goes out of scope.

You could probably also do it without moving actually, it just gets a little more complex.

[riku_iki]

I don't understand this, once Arena is gone, all contained objects will be destroyed altogether, that's the idea of Arena, no need to move them to GC control.