Sockets test fail on FreeBSD 12

[ararslan]

It seems #40783 broke one of the Sockets tests on FreeBSD 12:

julia/stdlib/Sockets/test/runtests.jl

Line 524 in 0224c42

@test !isopen(P) # eof test should have closed this by now

Following along the steps taken in the tests,

p = Pipe()
Base.link_pipe!(p)
write(p, "hello")
read(p, Char)
read(p, Char)
@async begin
    write(p, "w")
    while p.out.status != Base.StatusOpen
        yield()
    end
    close(p.in)
end
readuntil(p, 'w')
eof(p)

you'll get true from the final EOF check on any platform. However, p.out.status is Base.StatusEOF on FreeBSD with and Base.StatusClosed on macOS. Prior to #40783, p.out.status was Base.StatusClosed on both platforms.

[vtjnash]

Looking closer at the documentation for FreeBSD pipe, I see they are not fully posix-compatible since FreeBSD 2.2.1 https://www.freebsd.org/cgi/man.cgi?query=pipe&apropos=0&sektion=2&manpath=FreeBSD+2.2.1-RELEASE&arch=default&format=html, so it leads to surprises here.

[ararslan]

So would the issue be with how libuv is interacting with the OS's pipes or is it on the Julia side? (I guess it could be both)