walk_heap.rb

require 'objspace'
require 'config/environment'
require 'fiddle'
require 'fiddle/import'

extend Fiddle::Importer
include Fiddle
dlload

typealias "VALUE", "unsigned long"
Basic = ["VALUE flags", "VALUE klass"]

RUBY_FL_USHIFT          = 12

RUBY_T_IMEMO  = 0x1a # /*!< @see imemo_type */

RUBY_T_MASK   = 0x1f

RBasic = Class.new(struct Basic) do
  table = Object.constants.grep(/^RUBY_T_/).each_with_object({}) do |name, obj|
    obj[Object.const_get(name)] = name.to_s.sub(/^RUBY_/, '').to_sym
  end

  TYPE_TABLE = table

  def imemo?
    flags & RUBY_T_MASK == RUBY_T_IMEMO
  end

  def imemo_type
    (flags >> RUBY_FL_USHIFT) & 0x0f
  end

  def iseq?
    imemo_type == 7 # https://github.com/ruby/ruby/blob/dc03bdcefbf1fe062c0a7ad7fa5f6829866b8cab/internal.h#L852
  end
end

ptr = Handle::DEFAULT["rb_objspace_each_objects"]
rb_objspace_each_objects = Function.new(ptr, [TYPE_VOIDP, TYPE_VOIDP], TYPE_VOID)

ptr = Handle::DEFAULT["rb_iseqw_new"]
rb_iseq_new = Function.new ptr, [TYPE_VOIDP], TYPE_VOIDP

callback = Closure::BlockCaller.new TYPE_INT, [TYPE_VOIDP, TYPE_VOIDP, TYPE_INT, TYPE_VOIDP] do |vstart, vend, stride, data|
  while vstart != vend
    slot = RBasic.new(vstart)
    if slot.imemo? && slot.iseq?
      iseq = rb_iseq_new.call(vstart).to_value
      puts [iseq.size, iseq.markable_object_count].join ','
    end
    vstart += stride
  end
  0
end
GC.start
puts "size,markables"
rb_objspace_each_objects.call(callback, nil)