Issue #22139 has been updated by matz (Yukihiro Matsumoto). I agree with prohibiting `END{}` and `at_exit` in non-main Ractors (option 1). The current behavior is accidental rather than designed, and as I said before, invoking the block at the end of the Ractor (option 2) changes the meaning of `at_exit` too much. Option 3 is semantically consistent, but I doubt anyone actually wants blocks registered in a Ractor to fire on the main Ractor at process exit; the sharing/inheritance of reachable objects is also subtle. Starting with the simple prohibition is the right move. If real use cases emerge, we can relax it toward option 3 later, since going from an error to defined behavior is compatible. Matz. ---------------------------------------- Feature #22139: Prohibit `END{}`/`Kernel#at_exit` in non-main Ractor https://bugs.ruby-lang.org/issues/22139#change-118000 * Author: ko1 (Koichi Sasada) * Status: Closed ---------------------------------------- Let's prohibit `END{}`/`Kernel#at_exit` on non-main Ractor. The current behavior is strange: ```ruby Ractor.new{ at_exit{ p [self, Ractor.current] } } sleep 1 #=> [#<Ractor:#2 t.rb:2 terminated>, #<Ractor:#1 running>] ``` There are some options: 1. prohibit them. Simple. 2. invoke the block at the end of the Ractor. 3. invoke the block at the end of the process on main Ractor. It is similar idea of the current behavior. 2 is rejected clearly by Matz because of the semantic gap with current behavior. 3 is no problem because the block and reachable objects from the block can be inherited to main Ractor. However, to make it simple, now let's prohibit them (1), and revisit if we found the (3) is needed. -- https://bugs.ruby-lang.org/