From: "testredmine (Test Redmine)" <larry.kubin@...> Date: 2013-05-13T09:38:20+09:00 Subject: [ruby-core:54946] [Ruby 1.8 - Bug #4181] Backport Ruby 1.9 singleton.rb, since 1.8's is not thread-safe Issue #4181 has been updated by testredmine (Test Redmine). My 2 cents ---------------------------------------- Bug #4181: Backport Ruby 1.9 singleton.rb, since 1.8's is not thread-safe https://bugs.ruby-lang.org/issues/4181#change-39286 Author: headius (Charles Nutter) Status: Closed Priority: Normal Assignee: shyouhei (Shyouhei Urabe) Category: Target version: Ruby 1.8.7 ruby -v: Any Ruby 1.8 version =begin Ruby 1.9 modified singleton.rb by eliminating much of the lazy init logic, using a real mutex instead of Thread.critical, and eliminating the redefinition of "instance" on first call. None of these changes have been backported into a 1.8 release, which means all 1.8 releases have a broken singleton.rb. The following script breaks under any version of 1.8: <code> require 'singleton' $jruby = RUBY_PLATFORM =~ /java/ require 'jruby/synchronized' if $jruby loop do $inits = [] $inits.extend JRuby::Synchronized if $jruby classes = [] 1000.times do classes << Class.new do include Singleton end end (0..10).map do Thread.new do classes.each do |cls| cls.instance end end end.map(&:join) puts "loop completed" end </code> Results: ~/projects/jruby ��� ruby -v singleton_killer.rb ruby 1.8.7 (2010-08-16 patchlevel 302) [i686-darwin10.4.0] loop completed loop completed loop completed loop completed loop completed loop completed loop completed loop completed loop completed singleton_killer.rb:18: undefined method `instance' for #<Class:0x1001896a0> (NoMethodError) from singleton_killer.rb:1:in `join' from singleton_killer.rb:1:in `to_proc' from singleton_killer.rb:21:in `map' from singleton_killer.rb:21 from singleton_killer.rb:5:in `loop' from singleton_killer.rb:5 ~/projects/jruby ��� ruby -v singleton_killer.rb ruby 1.8.7 (2009-06-12 patchlevel 174) [universal-darwin10.0] loop completed loop completed loop completed loop completed singleton_killer.rb:18: undefined method `instance' for #<Class:0x100348c70> (NoMethodError) from singleton_killer.rb:1:in `join' from singleton_killer.rb:1:in `to_proc' from singleton_killer.rb:21:in `map' from singleton_killer.rb:21 from singleton_killer.rb:5:in `loop' from singleton_killer.rb:5 This can lead to lazy failures in any library that uses singleton.rb. See also this commit to Nokogiri, where they had to stop using Singleton because of this issue: https://github.com/tenderlove/nokogiri/commit/5eb036e39ea85a8e12eebee11bc5086b0e4ce6e3 =end -- http://bugs.ruby-lang.org/