Comment by cogman10

It seems like exactly the same verbosity as what you'd do with a custom allocator.

I think the only real grace is you don't have to pass around the allocator. But then you run into the issue where now anyone allocating needs to know about the lifetimes of the pool of the caller. If A -> B (pool) -> C and the returned allocation of C ends up in A, now you potentially have a pointer to freed memory.

Sending around the explicit allocator would allow C to choose when it should allocate globally and when it should allocate on the pool sent in.