ObjectSpace::define_finalizer says no

In Ruby, one has to be extremely careful when using ObjectSpace::define_finalizer. I fell for this trap:

	class C
	def initialize(id)
	@id = id
	self.class.finalize(self, id)
	end
	def self.finalize(obj, id)
	ObjectSpace.define_finalizer(obj, proc do
	puts "releasing a C with id = #{id}"
	end)
	end
	end

view raw define_finalizer1.rb hosted with ❤ by GitHub

See the problem here? Well, I didn't at first, until I noticed that my program only freed memory at shutdown. The problem here is that the proc is created with the obj instance as part of it's scope... or self, even if it isn't used inside the proc, which is the infamous ObjectSpace::define_finalizer bug.

To correct, I removed the obj parameter and called define_finalizer directly like so:

	class C
	def initialize(id)
	@id = id
	ObjectSpace.define_finalizer(self, self.class.finalize(id))
	end
	def self.finalize(id)
	proc do
	puts "releasing a C with id = #{id}"
	end
	end
	end

view raw define_finalizer2.rb hosted with ❤ by GitHub

This time around my computer started to say yes:

I hope this post may help someone, since I didn't find anything on the interwebs that exposed this specific issue.