> The sign bit has much more defined semantics regardless. But which of those semantics do we need for conveying which of two states something is in? If the L

> The sign bit has much more defined semantics regardless. But which of those semantics do we need for conveying which of two states something is in? If the Linux kernel recommended a more rich type for expressing the result of a syscall, compilers would find a way to express that portably. Or they wouldn't recommend it. Or compilers wouldn't make it portable. Or libc implementors won't use it. Or lots of other possibilities. And we keep living in the world where we kill a process (often init) when we forget to check a syscall result, and pass fd-or-error somewhere that takes an fd, because those things are both integers.