os: SetDeadline doesn't work after an Fd() call

[crvv]

What version of Go are you using (go version)?

go version devel +ed8b7dedd3 Thu Nov 30 01:46:50 2017 +0000 linux/amd64

What did you do?

package main

import (
    "os"
    "time"
)

func main() {
    r, w, err := os.Pipe()
    if err != nil { panic(err) }
    println(r.Fd())
    go func() {
        time.Sleep(time.Second*2)
        _, err := w.Write([]byte("Hello, world!"))
        if err != nil { panic(err) }
    }()
    err = r.SetDeadline(time.Now().Add(time.Second))
    // expect an error at this line
    if err != nil { panic(err) }
    buffer := make([]byte, 16)
    n, err := r.Read(buffer)
    // or this line
    if err != nil { panic(err) }
    println(string(buffer[:n]))
}

What did you expect to see?

A timeout error.
Or an error when SetDeadline.

The Fd() can also be called after SetDeadline(), so a timeout error is better.

What did you see instead?

A successful Read and "Hello, world!".

The method Fd() put the file descriptor into blocking mode and the deadline doesn't work after it.

go/src/os/file_unix.go

Line 68 in 8064f82

syscall.SetNonblock(f.pfd.Sysfd, false)

There is a similar issue with package net. #21862

[bradfitz]

Ian, I assume this is also just a documentation thing?

[gopherbot]

Change https://golang.org/cl/81636 mentions this issue: os: calling Fd disables the SetDeadline methods

[gopherbot]

Change https://golang.org/cl/82915 mentions this issue: net: calling File disables the SetDeadline methods