When I think of "arena" related to memory management, it's not about "flattening", but just an arena allocator ... When you're allocating a bunch of items with

When I think of "arena" related to memory management, it's not about "flattening", but just an arena allocator ... When you're allocating a bunch of items with the same lifetime, you can more efficiently allocate them from one or more large chunks of memory, and then at the end of their collective lifetime you free the large chunk(s) rather than freeing the items individually. The allocation can also be more efficient since you can just incrementally use the space in the parent chunk - no need for free-lists like a general purpose heap allocator. In this context, the "flattening" aspect of this - using indices rather than pointers - could be viewed just as using pointers (offsets) that are relative to the parent chunk.