[ruby-core:102117] [Ruby master Bug#17543] Ractor isolation broken by `self` in shareable proc

Issue #17543 has been updated by marcandre (Marc-Andre Lafortune).


Eregon (Benoit Daloze) wrote in #note-5:
> If it's needed to e.g. `Ractor.make_shareable(self); o = Ractor.make_shareable(Object.new); Ractor.make_shareable(-> { p o; ... })`, it feels so redundant.

I may be wrong, but I believe that in practice the objects that you will want to make shareable, and the blocks you want to make shareable will rarely if ever be related.

----------------------------------------
Bug #17543: Ractor isolation broken by `self` in shareable proc
https://bugs.ruby-lang.org/issues/17543#change-89972

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* ruby -v: 3.0.0p0
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
Discussing with @MaxLap we realized that the `self` in a shareable proc is not properly isolated:

```
class Foo
  attr_accessor :x

  def pr
    Ractor.make_shareable(Proc.new { self })
  end
end

f = Foo.new
f.x = [1, 2, 3]
Ractor.new(f.pr) { |pr| pr.call.x << :oops }
p f.x # => [1, 2, 3, :oops]
```

If the `self` refers to a shareable object then it's fine, but for non-shareable objects it has to be reset to `nil` or to a global shareable object that would have an instructive `inspect`.

```ruby
Ractor::DETACHED_SELF = Object.new
def << Ractor::DETACHED_SELF
  def inspect
    '<#detached self>'
  end
  alias to_s inspect
end
Ractor::DETACHED_SELF.freeze
```




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