From: "jhawthorn (John Hawthorn) via ruby-core" <ruby-core@...>
Date: 2025-07-03T00:39:53+00:00
Subject: [ruby-core:122647] [Ruby Bug#17359] Ractor copy mode is not Ractor-safe

Issue #17359 has been updated by jhawthorn (John Hawthorn).


Seems to still be an issue. Here's an updated reproduction for 3.5dev (Using Ractor::Port instead of take/yield)

``` ruby
class Foo
  attr_accessor :x

  def initialize_copy(*)
    $last = self
    super
  end
end
o = Foo.new
o.x = 42

port = Ractor::Port.new
r = Ractor.new(o, port) do |copy, port|
  puts copy.x # => 42
  port << :sync
  Ractor.receive
  puts copy.x # => 666
end
port.receive # => :sync
$last.x = 666
r.send :continue
r.join
```

----------------------------------------
Bug #17359: Ractor copy mode is not Ractor-safe
https://bugs.ruby-lang.org/issues/17359#change-113923

* Author: marcandre (Marc-Andre Lafortune)
* Status: Assigned
* Assignee: ractor
* ruby -v: ruby 3.0.0dev (2020-11-30T10:06:25Z master 89774a938a) [x86_64-darwin18]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
It should not be possible to mutate an object across Ractors, but the copy mode allows it currently:

```ruby
class Foo
  attr_accessor :x

  def initialize_copy(*)
    $last = self
    super
  end
end
o = Foo.new
o.x = 42

r = Ractor.new(o) do |copy|
  puts copy.x # => 42
  Ractor.yield :sync
  Ractor.yield :sync
  puts copy.x # => 666
end
r.take # => :sync
$last.x = 666
r.take # => :sync
r.take
```

Maybe the `copy` object should be marked as moved?



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