[ruby-core:121946] [Ruby Bug#21315] Finalizers violate the `rb_ractor_confirm_belonging` assertion

Issue #21315 has been updated by jhawthorn (John Hawthorn).


> When a Ractor terminates just before it actually does so it should probably run the remaining finalizers

Objects aren't necessarily unreferenced/garbage collectable at this point (they could have been made shareable, or be the return value taken by a another Ractor). I guess we could do this, but it does seem extremely surprising behaviour to run a finalizer on an accessible live object.

> For terminated Ractors I don't think it's a big deal, as long as we do what is necessary so that Ractor.current and Ractor local storage still work as expected.

The final return value of a Ractor is not made shareable, so the `take`-ing Ractor may have access with whatever objects were captured in the finalizer proc. I think we probably need to track that and forward the finalizer to the "next" Ractor (possibly following that several levels until we find a still-running Ractor).

----------------------------------------
Bug #21315: Finalizers violate the `rb_ractor_confirm_belonging` assertion
https://bugs.ruby-lang.org/issues/21315#change-113066

* Author: byroot (Jean Boussier)
* Status: Open
* Assignee: ractor
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Reproduction (with assertions enabled):

```ruby
require "tempfile"

Ractor.new do
  10.times do
    Tempfile.new
  end
end.take

GC.start
```

```
  <OBJ_INFO:rb_ractor_confirm_belonging@../src/ractor_core.h:375> (File)
  /home/runner/work/ruby/ruby/src/lib/tempfile.rb:387: [BUG] rb_ractor_confirm_belonging object-ractor id:1, current-ractor id:2
  ruby 3.5.0dev (2025-05-09T15:51:24Z pull/13291/merge e289a1dc58) +PRISM [x86_64-linux]
  
  -- Control frame information -----------------------------------------------
  c:0005 p:0007 s:0025 e:000024 METHOD /home/runner/work/ruby/ruby/src/lib/tempfile.rb:387 [FINISH]
  c:0004 p:0022 s:0020 e:000019 METHOD /home/runner/work/ruby/ruby/src/lib/prism/parse_result.rb:833 [FINISH]
  c:0003 p:---- s:0012 e:000011 CFUNC  :parse_lex_file
  c:0002 p:0006 s:0007 e:000006 BLOCK  /home/runner/work/ruby/ruby/src/test/prism/ractor_test.rb:26 [FINISH]
  c:0001 p:---- s:0003 e:000002 DUMMY  [FINISH]
  
  -- Ruby level backtrace information ----------------------------------------
  /home/runner/work/ruby/ruby/src/test/prism/ractor_test.rb:26:in 'block in test_parse_lex_file'
  /home/runner/work/ruby/ruby/src/test/prism/ractor_test.rb:26:in 'parse_lex_file'
  /home/runner/work/ruby/ruby/src/lib/prism/parse_result.rb:833:in 'initialize'
  /home/runner/work/ruby/ruby/src/lib/tempfile.rb:387:in 'call'
  
  -- Threading information ---------------------------------------------------
  Total ractor count: 2
  Ruby thread count for this ractor: 1
  
  -- C level backtrace information -------------------------------------------
  /home/runner/work/ruby/ruby/build/ruby(rb_print_backtrace+0x14) [0x561441aeedbf] ../src/vm_dump.c:843
  /home/runner/work/ruby/ruby/build/ruby(rb_vm_bugreport) ../src/vm_dump.c:1175
  /home/runner/work/ruby/ruby/build/ruby(bug_report_end+0x0) [0x561441aa3f39] ../src/error.c:1097
  /home/runner/work/ruby/ruby/build/ruby(rb_bug_without_die_internal) ../src/error.c:1097
  /home/runner/work/ruby/ruby/build/ruby(die+0x0) [0x5614416e237f] ../src/error.c:1115
  /home/runner/work/ruby/ruby/build/ruby(rb_bug) ../src/error.c:1117
  /home/runner/work/ruby/ruby/build/ruby(rb_ractor_confirm_belonging+0xde) [0x56144188c6be] ../src/ractor_core.h:376
  /home/runner/work/ruby/ruby/build/ruby(vm_exec_core+0xef) [0x5614418b23ef] /home/runner/work/ruby/ruby/build/vm.inc:2500
  /home/runner/work/ruby/ruby/build/ruby(rb_vm_exec+0x156) [0x5614418a4676] ../src/vm.c:2618
  /home/runner/work/ruby/ruby/build/ruby(vm_call0_cc+0x13d) [0x5614418aa1dd] ../src/vm_eval.c:101
  /home/runner/work/ruby/ruby/build/ruby(rb_vm_call0+0x4c) [0x5614418b1cc5] ../src/vm_eval.c:61
  /home/runner/work/ruby/ruby/build/ruby(rb_vm_call_kw) ../src/vm_eval.c:326
  /home/runner/work/ruby/ruby/build/ruby(rb_check_funcall_default_kw) ../src/vm_eval.c:694
  /home/runner/work/ruby/ruby/build/ruby(rb_gc_run_obj_finalizer+0x1cf) [0x56144170220f] ../src/gc.c:306
  /home/runner/work/ruby/ruby/build/ruby(rb_multi_ractor_p+0x0) [0x56144170246f] ../src/gc/default/default.c:2820
  /home/runner/work/ruby/ruby/build/ruby(rb_vm_lock_enter) ../src/vm_sync.h:74
  /home/runner/work/ruby/ruby/build/ruby(rb_gc_vm_lock) ../src/gc.c:137
  /home/runner/work/ruby/ruby/build/ruby(finalize_list) ../src/gc/default/default.c:2843
  /home/runner/work/ruby/ruby/build/ruby(finalize_deferred_heap_pages) ../src/gc/default/default.c:2866
```

I think it wouldn't be hard to disable that check when running a finalizer, but I don't know if it's the correct thing to do. 



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