[ruby-core:75877] [Ruby trunk Bug#11953] ThreadError in 2.3 on code that works on 2.2.4

Issue #11953 has been updated by Noah Gibbs.


The error is occurring in Singleton's instance method, which is mutex-protected.

Using the supplied example code, git-bisect points to this Ruby commit as the problem:

    commit d2487ed47587ec1cd1b456068e0af3ea0b39596d
    Author: marcandre <marcandre@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
    Date:   Fri May 22 13:36:39 2015 +0000
    
        * lib/prime.rb: Remove obsolete Prime.new
          patch by Ajay Kumar. [Fixes GH-891]
    
        git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50604 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

And that's where Prime switched from using a @the_instance member variable to using Singleton to track its instance.

So it looks like this code never worked with Prime as a Singleton.


----------------------------------------
Bug #11953: ThreadError in 2.3 on code that works on 2.2.4
https://bugs.ruby-lang.org/issues/11953#change-59055

* Author: Clayton Flesher
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 2.3.0
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
This is my first bug reporting, so I'm sorry if this isn't exactly correct format. I'll update my report accordingly if pointed in the right direction.

I ran into what appears to be a bug while doing a quiz.

I've included the breaking code, the test suite and the description of the quiz as attachments to this bug report.

The following code works fine on Ruby 2.2.4.

```ruby
class Prime
  def self.nth(num)
    error(num)
    primes = build_primes(num)
    primes.last
  end

  private

  def build_primes(num)
    primes = [2]
    index  = 3 
    until primes.size == num
      if example?(index, primes)
        primes << index
      end
      index += 1
    end
    primes
  end

  def error(num)
    unless num > 0
      raise ArgumentError
    end
  end

  def example?(index, primes)
    primes.each do |prime|
      if index % prime == 0
        return false
      end
    end
    true
  end
end
```

It raises this error in Ruby 2.3.0

```
ThreadError: deadlock; recursive locking
    /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `synchronize'
    /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `instance'
    /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:142:in `block in instance'
    /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `synchronize'
    /home/clayton/.rubies/ruby-2.3.0/lib/ruby/2.3.0/singleton.rb:140:in `instance'
    /home/clayton/exercism/ruby/nth-prime/nth_prime.rb:3:in `nth'
    nth_prime_test.rb:28:in `test_first'
```

If this is expected behavior, I'm sorry in advance for wasting your time.

---Files--------------------------------
nth_prime.rb (528 Bytes)
nth_prime_test.rb (973 Bytes)
README.md (1.27 KB)


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