[ruby-core:121419] [Ruby Bug#20934] `UnboundMethod#bind_call` may cause "double free or corruption" with Ractor

Issue #20934 has been updated by jhawthorn (John Hawthorn).

Assignee set to ractor

This should be fixed by bfe6068417ca41a6b88a1ba5fcde04f9a76718a7. I have some quick benchmark results in https://github.com/ruby/ruby/pull/12951, using the global lock wasn't too bad for performance and had basically no penalty single threaded, but it was easy enough to convert this reference count to use atomics.

----------------------------------------
Bug #20934: `UnboundMethod#bind_call` may cause "double free or corruption" with Ractor
https://bugs.ruby-lang.org/issues/20934#change-112402

* Author: wanabe (_ wanabe)
* Status: Closed
* Assignee: ractor
* ruby -v: ruby 3.4.0dev (2024-12-06T18:51:08Z :detached: 8ad6860ff7) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
When I call `UnboundMethod#bind_call` on both main Ractor and child Ractor, probable errors can be encountered.
Here is an issue reproduce script `ractor_issue.rb`.
```
def foo
  10000.times do
    Object.instance_method(:object_id).bind_call(self)
  end
end

Ractor.new { foo }
foo
```

And there are some examples of execution results.

```
$ ./miniruby -v ractor_issue.rb 
ruby 3.4.0dev (2024-12-06T18:51:08Z :detached: 8ad6860ff7) +PRISM [x86_64-linux]
ractor_issue.rb:7: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
double free or corruption (fasttop)
Aborted (core dumped)
```

```
$ ./miniruby -v ractor_issue.rb 
ruby 3.4.0dev (2024-12-06T18:51:08Z :detached: 8ad6860ff7) +PRISM [x86_64-linux]
ractor_issue.rb:7: warning: Ractor is experimental, and the behavior may change in future versions of Ruby! Also there are many implementation issues.
#<Thread:0x00007fc6c16bfb18 run> terminated with exception (report_on_exception is true):
ractor_issue.rb:3:in 'UnboundMethod#bind_call': undefined method 'object_id' for main (NoMethodError)
        from ractor_issue.rb:3:in 'block in Object#foo'
        from <internal:numeric>:257:in 'Integer#times'
        from ractor_issue.rb:2:in 'Object#foo'
        from ractor_issue.rb:8:in '<main>'
```

Please try running it several times, as there is a probability of successful completion.



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