> First count is the point of POSIX is any OS vendor doesn’t need to worry about any other OS compatibility. Just implement POSIX interfaces. I must be missing

> First count is the point of POSIX is any OS vendor doesn’t need to worry about any other OS compatibility. Just implement POSIX interfaces. I must be missing something. How are you getting from "just implement POSIX interfaces" to "compile once run everywhere"? Wouldn't the former just promise that you could compile the same source on any POSIX-compliant OSs and get a binary that runs on that OS, on that architecture?