Thanks a lot for the kind words and for buying the book!
Thank you for the list of issues. I have fixed 2, 3 and 4.
Regarding 1: There is no modern OS that leaks after shutdown. While there are some really old OSes where this could happen, Odin doesn’t support any of those OSes anyways. However, a good reason to do the deallocation at the end is to keep third-party memory analysis programs, such as Valgrind, happy. I have added a note about that in the book (update coming later today or tomorrow).