[ruby-core:101189] [Ruby master Bug#17359] Ractor copy mode is not Ractor-safe

[ko1@atdot.net]

Issue #17359 has been updated by ko1 (Koichi Sasada).


Eregon (Benoit Daloze) wrote in #note-7:
> An idea: copy everything in the source Ractor as currently, and then `move` the resulting copied object.
> That way, the source Ractor might keep references to copied objects, but it won't be able to use them.
> This actually means a partial copy for `move` on top of the original deep copy though.

Complete idea, but it makes two objects per one. mmm.

Doing it if user-defined `initialize_copy/clone` is detected?

----------------------------------------
Bug #17359: Ractor copy mode is not Ractor-safe
https://bugs.ruby-lang.org/issues/17359#change-88870

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* 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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