Because mon_initialized may be used to re-initialize copied objects intentionally.
mon_initialize_spec.rb fails:
1)
MonitorMixin#mon_initialize can be called in initialize_copy to get a new Mutex and used with synchronize ERROR
ThreadError: already initialized
/home/shugo/src/ruby/lib/monitor.rb:255:in `mon_initialize'
/home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:19:in `initialize_copy'
/home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:28:in `initialize_dup'
/home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:28:in `dup'
/home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:28:in `block (2 levels) in <top (required)>'
/home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:4:in `<top (required)>'
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65827 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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