From: "jhawthorn (John Hawthorn) via ruby-core" <ruby-core@...>
Date: 2026-11-12T19:42:03+00:00
Subject: [ruby-core:127453] [Ruby Bug#22084] invokesuper from define_method in Ractor can call wrong super method or crash

Issue #22084 has been updated by jhawthorn (John Hawthorn).

Backport changed from 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN to 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: DONE

This was backported to 4.0 back in June

https://github.com/ruby/ruby/pull/17154

----------------------------------------
Bug #22084: invokesuper from define_method in Ractor can call wrong super method or crash
https://bugs.ruby-lang.org/issues/22084#change-119906

* Author: jhawthorn (John Hawthorn)
* Status: Closed
* Assignee: ractor
* ruby -v: ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [arm64-darwin25]
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: DONE
----------------------------------------
`vm_search_super_method` has an odd behaviour where it allocates new callinfo (ci) and assigns it back to the iseq. All of our other method calls only reassign the callcache (cc). Because this CI is used from the iseq immediately after for method lookup or even later for the name in method_missing.

```ruby
N = Integer(ENV.fetch("N", "1000000"))

class Base
  def method_missing(mid, *) = mid
end

class Child < Base
  BODY = Ractor.shareable_proc { super() }
  define_method(:foo, &BODY)
  define_method(:bar, &BODY)
end

[:foo, :bar].map do |mid|
  Ractor.new(mid) do |mid|
    obj = Child.new
    N.times do
      got = obj.__send__(mid)
      raise "#{mid} returned #{got.inspect}" unless got == mid
    end
  end
end.each(&:value)
```

This will eventually result in method_missing being called with the wrong name

Another test also crashes on my arm-based M4 macbook pro. Which I think may be a memory ordering issue of the newly allocated callcache:

```ruby
N = Integer(ENV.fetch("N", "1000000"))

class Base
  def foo = :foo
  def bar = :bar
end

class Child < Base
  BODY = Ractor.shareable_proc { super() }
  define_method(:foo, &BODY)
  define_method(:bar, &BODY)
end

[:foo, :bar].map do |mid|
  Ractor.new(mid) do |mid|
    obj = Child.new
    N.times do
      got = obj.__send__(mid)
      raise "#{mid} returned #{got.inspect}" unless got == mid
    end
  end
end.each(&:value)
```

https://github.com/ruby/ruby/pull/17127



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