Impl new API std::os::unix::fs::mkfifo under feature unix_fifo

[NobodyXu]

Tracking issue #139324

[rustbot]

r? @tgross35

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[tgross35]

If this test is to be run (I think it's a good idea to have some form of test), it may be better to call mkdtemp and create the FIFO there to ensure it doesn't interfere with anyone who actually has a /tmp/fifo.

[NobodyXu]

I'm not sure if we can use libc::mktemp here...honestly maybe we should also add a function for that

[tgross35]

Agreed, it would be nice to have. libc isn't available but the binding is pretty easy, the setup is a bit clunky but I think it's worth avoiding any possible issues

/// # // Use a temporary file to avoid conflicts or cleanup issues
/// # extern "C" { fn mktemp(template: *mut c_char) -> *mut c_char; }
/// # let mut buf = b"rust-fifo-XXXXXX\0";
/// # let fname = unsafe {
/// #     let ptr = mktemp(buf.as_ptr().cast::<c_char>()) };
/// #     assert!(!ptr.is_null(), "could not create tempfile");
/// #     CStr::from_ptr(ptr).to_str().unwrap()
/// # };
/// mkfifo(fname, Permissions::from_mode(0o774))?;
/// // ...

The rest LGTM

[NobodyXu]

My problem with this is portability, not sure if it would work on musl, and probably android and other libc reliably.

If we want to do this, might be easier to random generate the filename using std::random?

[tgross35]

Fair point. We have tempfile for the std testsuite, maybe just make the doc example no_run and then add the actual test there?

[NobodyXu]

Yeah that makes more sense, I would do that

[tgross35]

I see this was made no_run but it doesn't look like a test wasn't added. If you don't have it yet, just copy+paste this example to std/src/os/unix/fs/tests.rs using a file name from crate_helpers::tmpdir().join("fifo").

[tgross35]

@rustbot author for the failing test and review

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[NobodyXu]

I really have no idea why this fails on x86_64-unknown-linux-gnu, I added the new function for all unix target, but somehow it's missing on linux...

[NobodyXu]

@rustbot ready