Unsoundness in `<SockRef as From<&AsRawFd>>::from`

[coolreader18]

You can do something like:

let sock = socket2::SockRef::from(&-1);
assert!(Some(sock).is_none());

With the changes in #222

[Thomasdezeeuw]

This is the same problem as being discussed in #229, SockRef::from needs to ensure the RawFd is valid, but currently doesn't.

[Thomasdezeeuw]

Whoops I meant #218.

[coolreader18]

Ah, sorry about that, shoulda checked.

[coolreader18]

Oh, wait, I'll add this to that discussion, but this is actually unsound language-wise, not just questionably unsafe/non-private - because of the niche optimization from #222, you can create an invalid value in safe code.

[Thomasdezeeuw]

Oh, wait, I'll add this to that discussion, but this is actually unsound language-wise, not just questionably unsafe/non-private - because of the niche optimization from #222, you can create an invalid value in safe code.

You're right using -1 is even worse, but as #222 is talking about a redesign I though it best to not have two concurrent threads talking about the same thing. But this is definitely blocking a v0.4.1 release (which would include #222).