TcpSocket try_clone() sets close-on-exec but this isn't documented

[setharnold]

Hello, the TcpSocket try_clone() method calls into .duplicate(), which sets the close-on-exec flag on the socket:

https://doc.rust-lang.org/src/std/net/tcp.rs.html#255-257
https://github.com/rust-lang/rust/blob/master/src/libstd/sys/unix/fd.rs#L197

I believe the documentation for try_clone() should be extended to describe:

• That this is an operation with the underlying operating system, dup() or WSADuplicateSocket() or whatever is appropriate (this would help address very similar issue 45536)
• That the duplication operation also sets the close-on-exec flag.

Thanks

[frewsxcv]

@rust-lang/libs checking with y'all before a PR gets opened for this – is it okay to specify that close-on-exec flag (CLOEXEC) gets set as a platform-specific behavior for TcpStream::try_clone?

[alexcrichton]

@frewsxcv ah yeah every file descriptor libstd creates has CLOEXEC, so this should be good to document

[frewsxcv]

so next step here is deciding how to document this. i imagine there are a bunch of APIs in the standard library that create file descriptors. would it be excessive to add a # Platform-specific behavior to each of these APIs mentioning which platforms set CLOEXEC?

[steveklabnik]

@frewsxcv yup!

[LFS6502]

@rustbot claim

[AprilNEA]

@rustbot claim