Issue #20485 has been updated by skhrshin (Shintaro Sakahara). I tried looping with `100.times` in a more complex case that I created in the middle of the entire investigation of a test suite whose memory usage keeps growing until getting killed due to OOM, and as you said, the "leaked" object remaining was only one. So I conclude that this behavior is not a problem. I apologize for wasting your time. Thank you for the great help. ---------------------------------------- Bug #20485: Simple use of Fiber makes GC leak objects with singleton method https://bugs.ruby-lang.org/issues/20485#change-108269 * Author: skhrshin (Shintaro Sakahara) * Status: Open * ruby -v: ruby 3.2.4 (2024-04-23 revision af471c0e01) [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- I found a possible memory leak which occurs only when several conditions are met. The code to reproduce the problem is below: ``` class Work def add_method singleton_class.define_method(:f) {} end end 1.times { Fiber.new {}.resume } work = Work.new work.add_method work = nil GC.start num_objs = ObjectSpace.each_object.select { |o| o.is_a?(Work) rescue false }.size unless num_objs.zero? raise "NG" end ``` Expected result: The script exits normally. Actual result: RuntimeError "NG" is raised. If I change `1.times { Fiber.new {}.resume }` to just `Fiber.new {}.resume` or remove `work.add_method`, GC works as expected. Is there any problem at the way to use Fiber in this code, or is it a bug due to Ruby? I tested ruby 3.3.1 (2024-04-23 revision c56cd86388) [x86_64-linux] too and the result was a little different. The code above didn't reproduce the problem, but if I changed `1.times` to `Mutex.new.synchronize`, it was able to reproduce. -- https://bugs.ruby-lang.org/