Issue #16788 has been updated by ana06 (Ana Maria Martinez Gomez).


@jeremyevans0 thank you so much for your answer. Why are two singleton classes created and why only the second one is accesible to the user?

Also, could you please tell me how do you do to see the debugger output?


----------------------------------------
Bug #16788: T_CLASS counts classes double
https://bugs.ruby-lang.org/issues/16788#change-85141

* Author: ana06 (Ana Maria Martinez Gomez)
* Status: Rejected
* Priority: Normal
* ruby -v: 1.9 to master
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
Consider the following code:

``` ruby
h = {}
ObjectSpace.count_objects(h)
puts "Counts: #{ h[:T_CLASS] }, #{ h[:T_ICLASS] }"

objects = []
classes = []
ObjectSpace.each_object(Object){|x| objects << x}
ObjectSpace.each_object(Class){|x| classes << x}

class Test
end

objects2 = []
classes2 = []
ObjectSpace.each_object(Object){|x| objects2 << x}
ObjectSpace.each_object(Class){|x| classes2 << x}

objects_ids = objects.map(&:object_id)
new_objects = objects2.reject { |e| objects_ids.include? e.object_id }

puts "New objects belongs to the classes: #{ new_objects.map(&:class).uniq }"
puts "New classes: #{classes2 - classes}"

h = {}
ObjectSpace.count_objects(h)
puts "Counts: #{ h[:T_CLASS] }, #{ h[:T_ICLASS] }"
```

The result is the following:
```
Counts: 690, 46
New objects belongs to the classes: [Array, Class]
New classes: [Test]
Counts: 692, 46
```

This means that the number of `T_CLASS` is increased by 2 with the creation of 1 class. Why is this the case? Is this a bug?

Consider the slightly modified code with:
``` ruby
class Test
  def self.foo 
  end
end
```
In this case the Singleton class is also created and the results are:

```
Counts: 690, 46
New objects belongs to the classes: [Array, Class]
New classes: [#<Class:Test>, Test]
Counts: 693, 46

```

In this case, `T_CLASS` is increased by 3. So it seems like the issue is only with normal classes and not singleton ones.

From https://stackoverflow.com/questions/61031735
 






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