[ruby-core:102300] [Ruby master Bug#17543] Ractor isolation broken by `self` in shareable proc

[eregontp@gmail.com]

Issue #17543 has been updated by Eregon (Benoit Daloze).


ko1 (Koichi Sasada) wrote in #note-10:
> choose `nil` for self for sharable Proc? No special constant is needed.

That sounds confusing, if e.g., the NoMethodError comes from a line like `[foo, bar.foo]`, is it because `self` is nil or because `bar` returns `nil`?
Seems impossible to know if detached self is `nil`.

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Bug #17543: Ractor isolation broken by `self` in shareable proc
https://bugs.ruby-lang.org/issues/17543#change-90155

* 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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