From: Eric Wong <normalperson@...>
Date: 2011-08-27T19:54:58+09:00
Subject: [ruby-core:39140] [Ruby 1.9 - Bug #5237] IO.copy_stream calls #read on an object infinitely many times


Issue #5237 has been updated by Eric Wong.

File 0001-avoid-infinite-loop-of-IO.copy_stream.patch added

The class that implements an IO#read-like method without clearing
the destination buffer on EOF is arguably broken, but infinite
looping is bad, I think.

The attached simple patch should fix the issue.  Also available via git:
  git pull git://bogomips.org/ruby.git copy-stream-infinite-loop

----------------------------------------
Bug #5237: IO.copy_stream calls #read on an object infinitely many times
http://redmine.ruby-lang.org/issues/5237

Author: Brian Ford
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 
ruby -v: ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]


The code for IO.copy_stream appears to support passing any object that implements #readpartial or #read. For example, passing an instance of StringIO works just fine:

sasha:rubinius2.0 brian$ irb
ruby-1.9.2-p290 :001 > puts RUBY_DESCRIPTION
ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
 => nil 
ruby-1.9.2-p290 :002 > require 'stringio'
 => true 
ruby-1.9.2-p290 :003 > s = StringIO.new "this is a test"
 => #<StringIO:0x00000100851190> 
ruby-1.9.2-p290 :004 > IO.copy_stream s, "copy_stream_stringio"
 => 14 
ruby-1.9.2-p290 :005 > IO.read "copy_stream_stringio"
 => "this is a test" 
ruby-1.9.2-p290 :006 > 

However, passing an object that implements eg #read according to the specification of IO#read, causes IO.copy_stream to endlessly call #read on the object:

class A
  def initialize
    @count = 0
  end

  def read(bytes, buffer)
    print "read: #{@count += 1}\r"
    buffer.replace "this is a test"
    return nil
  end
end

a = A.new
IO.copy_stream a, "copy_stream_test"

ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
copy_stream_bug.rb:7:in `write': Interrupt
	from copy_stream_bug.rb:7:in `print'
	from copy_stream_bug.rb:7:in `read'
	from copy_stream_bug.rb:14:in `copy_stream'
	from copy_stream_bug.rb:14:in `<main>'

Thanks,
Brian


-- 
http://redmine.ruby-lang.org