From: Charles Nutter Date: 2011-01-10T16:16:46+09:00 Subject: [ruby-core:34292] [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 Charles Nutter. require 'thread' is required to get Mutex, which the 1.9 version uses to safely define the singleton. I think the requirement that singleton.rb requires thread.rb is ok. ---------------------------------------- http://redmine.ruby-lang.org/issues/show/4181 ---------------------------------------- http://redmine.ruby-lang.org