[toast0]

In a virtual memory operating system, every program has its own address space. Accessing an unmapped address is not the same as trying to access another process's memory.

It's also pretty common to use memory protection to autoextend stacks... Allocate the stack size you need, ask the OS to mark the page(s) after the stack as protected, catch the signal when you hit the protection, allocate some more stack and a new protected page unless the stack is too big. Works for heaps too.

Let the MMU hardware check accesses, so you don't have to check everything in software all the time.