It is an allocation bug, it's a use-after-free. It's only a UAF if you actually ...

afdbcreid 56 days ago | parent | context | favorite | on: Zig: Pointer Stability for ArrayLists

It is an allocation bug, it's a use-after-free. It's only a UAF if you actually have a reallocation (something that happens in the given example), but debug allocators don't require you to annotate your code.