Bug #11828: Object#freeze grid-locks Ruby

• Status: Rejected
• Assignee: -
• Target version: -
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[danielpclark (Daniel P. Clark)]

It seems safe to freeze most any class type in Ruby. But if you call Object.freeze nothing from then on can be created in either class of method form.

Is this okay behavior to have in Ruby?

Object.freeze

class A
end
# => RuntimeError: can't modify frozen #<Class:Object>

def x
end
# => RuntimeError: can't modify frozen class

I noticed that Procs can still be defined.

prc = proc {|a| a+1}

prc.call(4)
# => 5 

But all singleton instances are frozen.

[shugo (Shugo Maeda)]

• Status changed from Open to Feedback

Daniel P. Clark wrote:

It seems safe to freeze most any class type in Ruby. But if you call Object.freeze nothing from then on can be created in either class of method form.

Is this okay behavior to have in Ruby?

Object.freeze

class A
end
# => RuntimeError: can't modify frozen #<Class:Object>

The above code tries to define the constant A in Object, so a RuntimeError is raised.

def x
end
# => RuntimeError: can't modify frozen class

The above code tries to define the method x in Object, so a RuntimeError is raised.

The following code avoiding such operations on Object works correctly even if Object is frozen:

a = Class.new {
  def foo
    puts "foo"
  end
}

a.new.foo

But all singleton instances are frozen.

What does "all singleton instances" mean?

[danielpclark (Daniel P. Clark)]

Thank you for your reply. I've found your explanation most helpful.

What does "all singleton instances" mean?

Object.freeze

Enumerable.singleton_class.tap {def a; end}
# => RuntimeError: can't modify frozen class

Kernel.singleton_class.tap {def a; end}
# => RuntimeError: can't modify frozen class

Enumerator::Lazy.singleton_class.tap {def a; end}
# => RuntimeError: can't modify frozen class

UPDATE: My mistake... I was using tap wrong again. It appears singleton_class is still modifiable.

Enumerator.tap {|i| def i.a; end}
# => Enumerator 
Enumerator.respond_to? :a
# => true

I was wrong about my last statement.

[shugo (Shugo Maeda)]

• Status changed from Feedback to Rejected

Daniel P. Clark wrote:

What does "all singleton instances" mean?

Object.freeze

Enumerable.singleton_class.tap {def a; end}
# => RuntimeError: can't modify frozen class

Kernel.singleton_class.tap {def a; end}
# => RuntimeError: can't modify frozen class

Enumerator::Lazy.singleton_class.tap {def a; end}
# => RuntimeError: can't modify frozen class

UPDATE: My mistake... I was using tap wrong again. It appears singleton_class is still modifiable.

Enumerator.tap {|i| def i.a; end}
# => Enumerator 
Enumerator.respond_to? :a
# => true

I was wrong about my last statement.

Ah, I see. Thanks for your confirmation.

So I close this ticket.