For sure, writing your own allocator is the last thing you reach for after all else fails. I've never needed to do so in practice. My allocator was fast because it had no thread safety, no debugging features, raw pointer arithmetic (hard to read code), and no/optional error checking.

> For sure, writing your own allocator is the last thing you reach for after all else fails.

Writing your own general purpose allocator might be the last thing, but custom allocators for well-understood limited/localized behavior is both trivial and something one should do even for simplification in many cases. Freeing an entire arena/resetting an allocation pointer is both much faster and simpler than `malloc`/`new` & `free`/`delete`.

People often misunderstand "custom allocators" to mean "making your own `jemalloc`" and it feels like your comment runs the risk of fueling that fire. Creating your own `jemalloc` is both wasteful in that `jemalloc` performs worse than even the most simple of custom allocators and a waste of your time in that general purpose allocators already exist so if you need something like that you probably can save your time for something else.