This may be practically correct, but is semantically very very wrong.

size_t represents the size of objects in memory. So of course it scales with virtual memory space.

ssize_t is like size_t (same width), but signed. It's useful for routines that want to return a size_t or error (network routines like send/recv).

ptrdiff_t is specifically for the result of subtracting one pointer from another. Obviously it scales with pointer size as well.