[ruby-core:125581] [Ruby Bug#22084] invokesuper from define_method in Ractor can call wrong super method or crash

28 May 2026

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

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

* Author: jhawthorn (John Hawthorn)
* Status: Open
* 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: UNKNOWN
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`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)
```

```
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)
```

Both of these will eventually result in the wrong parent method being called (or method_missing with the wrong name). Less often they may also segfault.

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

-- 
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