Koichi Sasada 5c2b644166 fix random EBADF problem ...

```ruby
      r, w = IO.pipe
      r.close

      IO.for_fd(w.fileno).close
```

This code closes a file descriptor `w.fileno`, but `w` doesn't know
the closing. Another code can open same file descriptor with opening
file (`f`). After that, the `w` will GCed and `w.fileno` is closed
again, and `f.fileno` is closed too, so IO operations for `f` (`f.close`)
will cause EBADF.

To fix this issue, do this test in another process.

2021-10-26 11:39:52 +09:00

..

test_wait.rb

…