Regardless of focusing on correctness or performance, it looks to me like the author didn’t understand arenas that well.
Like the other commenter said, “You use an arena when you have computation that might consume a bunch of scratch memory, and then you want to free all of that memory at once when the computation is done.” That’s the entire point of arenas.
Like the other commenter said, “You use an arena when you have computation that might consume a bunch of scratch memory, and then you want to free all of that memory at once when the computation is done.” That’s the entire point of arenas.