From: "Eregon (Benoit Daloze)" <noreply@...>
Date: 2021-10-06T18:39:31+00:00
Subject: [ruby-core:105576] [Ruby master Bug#18243] Ractor.make_shareable does not freeze the receiver of a Proc but allows accessing ivars of it

Issue #18243 has been updated by Eregon (Benoit Daloze).


Smaller repro:
```
$ ruby -e 'Object.new.instance_eval { p object_id; proc = Ractor.make_shareable -> { self }; Ractor.new(proc) { |c| p c.call.object_id }.take }'
60
<internal:ractor>:267: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
60
```

In contrast to:
```
$ ruby -e 'a=Object.new; Ractor.make_shareable -> { a }'
<internal:ractor>:816:in `make_shareable': can not make shareable Proc because it can refer unshareable object #<Object:0x00007fd8bdd8f688> from variable `a' (Ractor::IsolationError)
	from -e:1:in `<main>'
```

It seems there is no check for `self` but there should be, it's like a capture local variable.

Either it raises like for local vars or it `Ractor.make_shareable` the `self`.

If it raises ostruct.rb will break but that's fixable by `Ractor.make_shareable self` first which is probably best for clarity anyway, cc @marcandre.

----------------------------------------
Bug #18243: Ractor.make_shareable does not freeze the receiver of a Proc but allows accessing ivars of it
https://bugs.ruby-lang.org/issues/18243#change-94034

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
```ruby
c = C.new
c.foo = 1
p c
proc = c.setter_proc
p c.frozen?
Ractor.new(proc) { |s| s.call(42) }.take
p c
```
gives
```
#<C:0x00007f2a3aae7a98 @foo=1>
false
#<C:0x00007f2a3aae7a98 @foo=42> # BUG
```

But that must be a bug, it means the non-main Ractor can directly mutate an object from the main Ractor.

I found this while thinking about https://github.com/ruby/ostruct/pull/29/files and
whether `Ractor.make_shareable` would freeze `@table` and the `OpenStruct` instance (I think it needs to).

Repro code for ostruct and changing ostruct.rb to `$setter = ::Ractor.make_shareable(setter_proc)`:
```ruby
require 'ostruct'

os = OpenStruct.new
os.foo = 1

$setter.call(2)
p os

Ractor.new($setter) { |s| s.call(42) }.take
p os
```
gives
```
#<OpenStruct foo=2>
<internal:ractor>:267: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
#<OpenStruct foo=42> # BUG
```



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