One of the benefits of the arena that the OP mentions though is that old pointers are still valid as long as the arena is still valid. That's not necessarily th

One of the benefits of the arena that the OP mentions though is that old pointers are still valid as long as the arena is still valid. That's not necessarily the case with realloc. Interesting idea to skip explicitly tracking capacity with realloc though. That does seem convenient, and if the allocator is fast, sure, why not?