Bug #1460: IO#select returns wrong fd list after Kernel#sleep (Windows)

• Status: Rejected
• Assignee: usa (Usaku NAKAMURA)
• Target version: Ruby 1.8.6
• ruby -v: ruby 1.8.6 (2008-08-11 patchlevel 287) [i386-mswin32]

[romuloceccon (Rômulo Ceccon)]

=begin
The following script never ends on Windows XP/Vista:

require 'thread'

a = IO.pipe
puts "pipe: #{a.inspect}"

th = Thread.new do
if res = IO.select([a[0]], [], [], 1)
puts "select ok: #{res.inspect}"
c = a[0].read(1)
puts "read ok: #{c}"
else
puts "timeout"
end
end

puts "sleep"
sleep(1)
puts "done"

The main thread stops at "sleep(1)" and the secondary thread at "c = a[0].read(1)". This is the output I get:

pipe: [#IO:0x2b616f4, #IO:0x2b616cc]
sleep
select ok: #<a href="IO:0x2b616f4" class="external">IO:0x2b616f4</a>], [], [
(ruby freezes here)

The Kernel#sleep call makes IO#select return with the pipe handle, even though it hasn't signaled. Then the call to IO#read blocks because no data is available. I couldn't come up with a workaround because IO#read_nonblock does not work with pipes in Windows (raises "Bad file descriptor" (calling IO#fcntl with O_NONBLOCK is also not possible)).
=end

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Assigned
• Assignee set to usa (Usaku NAKAMURA)

=begin
Don't use IO.select with pipes. It's a known restriction.
If you really need to it, use 1.8.7.
=end

[usa (Usaku NAKAMURA)]

• Status changed from Assigned to Rejected

=begin

=end