memory_held_by_closures.rb

BIG_BEFORE="big before"
BIG_AFTER="big after"
GARBAGE="garbage"
REGEXP=/big /

$big_after_id = 0
$big_before_id = 0
$callable_id = 0

$use_proc = true

class Callable
  def call
    "whatever"
  end
end

def thing
  big_before_object = BIG_BEFORE*500_000
  $big_before_id = big_before_object.object_id

  if $use_proc
    returned_proc = proc { |x| big_before_object }
  end

  big_after_object = BIG_AFTER*500_000
  $big_after_id = big_after_object.object_id

  if $use_proc
    returned_proc
  else
    Callable.new
  end
end

def show_gc
  GC.start
  ids = ObjectSpace.each_object.map(&:object_id)
  puts "Before: #{ids.include?($big_before_id)}"
  puts "After: #{ids.include?($big_after_id)}"
  puts "Callable: #{ids.include?($callable_id)}"
end

puts "Uses proc: #{$use_proc}\n\n"

callable = thing
$callable_id = callable.object_id

show_gc

puts "\n\nZapping the callable\n\n"
callable = nil

show_gc