I wouldn't call any of these things a "bug", in the sense of a behavior that departs from an explicit or implicit specification. Some of them are just advantage

I wouldn't call any of these things a "bug", in the sense of a behavior that departs from an explicit or implicit specification. Some of them are just advantages and disadvantages of that overall approach. Also, I'm disappointed that VM languages don't turn SIGBUS accessing a memory mapped region into a VM exception. They could, and it wouldn't even be that hard.