Ruby dup/clone behavior

dup.rb

class A
  def initialize_dup(other)
    puts 'init dup'
    super
  end

  def initialize_clone(other)
    puts 'init clone'
    super
  end

  def initialize_copy(other)
    puts 'init copy'
    super
  end
end

class B < A
  def initialize_dup(other)
    puts 'B init dup'
  end

  def initialize_clone(other)
    puts 'B init clone'
  end

  def initialize_copy(other)
    puts 'B init copy'
  end
end

class C < A
  def initialize_dup(other)
    puts 'C init dup'
    super
  end

  def initialize_clone(other)
    puts 'C init clone'
    super
  end

  def initialize_copy(other)
    puts 'C init copy'
    super
  end
end

def debug(klass)
  puts "#{klass.name} =="
  puts 'dup'
  klass.new.dup
  puts 'clone'
  klass.new.clone
  puts '---'
end

debug A
debug B
debug C


=begin
### Output
$ ruby dup.rb 
A ==
dup
init dup
init copy
clone
init clone
init copy
---
B ==
dup
B init dup
clone
B init clone
---
C ==
dup
C init dup
init dup
C init copy
init copy
clone
C init clone
init clone
C init copy
init copy
---
=end