Ruby allocation calling mixin

allocations.rb

module Foo
  def foo
    bar
  end

  def bar
  end
end

class Whatever
  include Foo
end

class SomethingElse
  def foo
    bar
  end

  def bar
  end
end

something_else = SomethingElse.new
start = GC.stat(:total_allocated_objects)
something_else.foo
puts GC.stat(:total_allocated_objects) - start
# => 0 (this is what I expected)

whatever = Whatever.new
start = GC.stat(:total_allocated_objects)
whatever.foo
puts GC.stat(:total_allocated_objects) - start
# => 2 (huh)?

Using rspec-memory to capture this but didn't get any clear picture.

#!/usr/bin/env ruby

require 'rspec/memory/trace'

module Foo
  def foo
    bar
  end

  def bar
  end
end

class Whatever
  include Foo
end

class SomethingElse
  def foo
    bar
  end

  def bar
  end
end

something_else = SomethingElse.new
start = GC.stat(:total_allocated_objects)
something_else.foo
puts GC.stat(:total_allocated_objects) - start
# => 0 (this is what I expected)

trace = RSpec::Memory::Trace.new([])

trace.capture do
	whatever = Whatever.new
	whatever.foo
end

pp trace

gives

0
#<RSpec::Memory::Trace:0x00007f96ef07e7d8
 @allocated={},
 @ignored={Whatever=>#<struct RSpec::Memory::Allocation count=1, size=0>},
 @klasses=[],
 @retained={},
 @total=#<struct RSpec::Memory::Allocation count=1, size=0>>

That means it can't be a Ruby object but some internal data structure allocated by Ruby.