Issue #22106 has been reported by miles-georgi (Miles Georgi). ---------------------------------------- Bug #22106: Getting a segfault when using finalizers and/or WeakMap in Ractors https://bugs.ruby-lang.org/issues/22106 * Author: miles-georgi (Miles Georgi) * Status: Open * ruby -v: ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [x86_64-linux] * Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- If I run the following script I get a segfault: ```ruby def ractor_and_port_counts total_ractor_count = total_ractor_port_count = open_ractor_count = open_ractor_port_count = 0 ObjectSpace.each_object do |object| case object when Ractor total_ractor_count += 1 open_ractor_count += 1 unless object.default_port.closed? when Ractor::Port total_ractor_port_count += 1 open_ractor_port_count += 1 unless object.closed? end end [total_ractor_count, open_ractor_count, total_ractor_port_count, open_ractor_port_count] end def show_ractor_counts GC.start pp ractor_and_port_counts end class Wrapper class << self def finalizer_proc proc do |id| wrapper_to_ractor = Ractor[:wrapper_to_ractor] if wrapper_to_ractor wrapper_to_ractor[id]&.each_key { |ractor| ractor << :close } rescue Ractor::ClosedError end end end def setup_finalizer(wrapper) wrapper_to_ractor = Ractor[:wrapper_to_ractor] ||= {} map = wrapper_to_ractor[wrapper.object_id] ||= ObjectSpace::WeakMap.new map[wrapper.ractor] = true ObjectSpace.define_finalizer(wrapper, &finalizer_proc) end end attr_reader :ractor def initialize(object) @ractor = Ractor.new do loop { break if receive == :close } o = nil end @ractor.send(object, move: true) self.class.setup_finalizer(self) end end class Outer def initialize = @inner = Wrapper.new(Inner.new) end class Inner; end show_ractor_counts outer = Wrapper.new(Outer.new) show_ractor_counts outer = nil # Removing the following line makes it so it only segfaults sometimes instead of everytime show_ractor_counts ``` I'll attach the script and the whole segfault but part of the segfault is: ``` <internal:gc>:44: [BUG] FL_FINALIZE flag is set, but finalizers are not found ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [x86_64-linux] -- Control frame information ----------------------------------------------- c:0004 p:0010 s:0023 e:000018 l:y b:0001 METHOD <internal:gc>:44 c:0003 p:0004 s:0011 e:000010 l:y b:0001 METHOD test_scripts/finalizer-in-ractor-test-segfault:23 c:0002 p:0075 s:0007 E:000f98 l:n b:---- EVAL test_scripts/finalizer-in-ractor-test-segfault:72 [FINISH] c:0001 p:0000 s:0003 E:000b40 l:y b:---- DUMMY [FINISH] -- Ruby level backtrace information ---------------------------------------- test_scripts/finalizer-in-ractor-test-segfault:72:in '<main>' test_scripts/finalizer-in-ractor-test-segfault:23:in 'show_ractor_counts' <internal:gc>:44:in 'start' ``` This happens in both a local build of 4.1-dev and 4.0.5 I suspect one might need to put GC.start at the end of the script if unable to reproduce. ---Files-------------------------------- segfault.txt (22 KB) finalizer-in-ractor-test-segfault (1.66 KB) -- https://bugs.ruby-lang.org/