Bug #18243
Updated by Eregon (Benoit Daloze) almost 3 years ago
```ruby
class C
attr_accessor :foo
def setter_proc
Ractor.make_shareable(-> v { @foo = v })
end
end
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
```