> dubiously-safe

No, it's perfectly safe. Except if you expand the scope of "safe" by a lot.

OP turned the socket into an (almost) raw file descriptor, and created an UDP socket from it. Weird, yes, but since it's perfectly memory safe and invalid operations would correctly error, it's not "dubiously-safe". It's safe.

I mean, either your language has the ability to do raw (technically Owned in this case) file descriptors, or it doesn't.

Maybe you'd prefer Rust had a third mode? Safe, `unsafe {}`, and `are_you_sure_you_understand_this {}`, the last one also being 'safe', but just… odd.

▲ antonvs 22 minutes ago | parent [-]

It's dubiously safe because it allows invalid combinations, i.e. calling UDP-related methods on non-UDP sockets. I'm using "safe" in the general English sense here, "protected from or not exposed to danger or risk."

> invalid operations would correctly error

At runtime, yes. I'm pointing out that Rust makes it possible to do better, and catch such issues at compile time.

	▲	knorker 8 minutes ago \| parent [-]
		Of course it allows invalid combinations. This also compiles: `let f = std::fs::File::open("/dev/null").unwrap(); let f: std::os::fd::OwnedFd = f.into(); let socket: std::net::UdpSocket = f.into();` If you convert a high level object into a low level one, and then back up as another type, then what exactly do you expect the language to do about that? > "protected from or not exposed to danger or risk." A computer will do what you tell it to do, not what you intend it to do. Opening a file is way more dangerous than risking errors because "this syscall doesn't work on that fd". There's also always risk that a syscall will fail at runtime, whether the type of fd is correct or not. It sounds like you would prefer if UdpSocket From<OwnedFD> should run getsockname() or something to confirm it's of the expected type, but I would prefer not. Indeed, in the general case some perfectly coded `unsafe` code could `dup2()` over the fd, so any checking at UdpSocket creation time is moot; you still don't get the safety you are asking for.