Undead blocks

block-leak.rb

#!/usr/bin/env ruby

require 'weakref'

class Proxy < BasicObject
  attr_reader :cls

  def initialize(cls)
    @cls = cls
  end

  def method_missing(meth, *args, &block)
    cls.public_send(meth, *args, &block)
  end
end

class Hidden
  attr_reader :proxy

  def self.pcls(cls)
    Proc.new {p cls}
  end

  def initialize(cls)
    @cls = cls
    @proxy = Proxy.new(cls)

    if true # if true then reference to `cls` is never released
      self.class.send(:define_method, 'cls') do |*args, &block|
        p @cls
      end
    else
      self.class.send(:define_method, 'cls', &Hidden.pcls(cls))
    end
  end
end

class Test
  attr_reader :foo

  def initialize(foo)
    @foo = foo
  end

  def self.new(*args, &block)
      proxy = Hidden.new(allocate).proxy
      proxy.send(:initialize, *args, &block)
      proxy
  end
end

test = Test.new 'foo'
p test.foo
weak = WeakRef.new test
test = nil

puts 'Wait'
loop do
  GC.start
  break unless weak.weakref_alive?
end
puts 'PASS' unless weak.weakref_alive?
sleep 1