From: Chauk-Mean P <chauk.mean@...>
Date: 2007-03-22T18:00:09+09:00
Subject: BUGS in metaclasses inheritance

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Hi all,

It will probably not change the world but I've found 3 bugs regarding the
inheritance between metaclasses both in Ruby 1.8.5 and 1.8.6.

The inheritance should be as defined in the object.c source code (best seen
with a fixed font) :

 *                            +------------------+
 *                            |                  |
 *              Object---->(Object)              |
 *               ^  ^        ^  ^                |
 *               |  |        |  |                |
 *               |  |  +-----+  +---------+      |
 *               |  |  |                  |      |
 *               |  +-----------+         |      |
 *               |     |        |         |      |
 *        +------+     |     Module--->(Module)  |
 *        |            |        ^         ^      |
 *   OtherClass-->(OtherClass)  |         |      |
 *                              |         |      |
 *                            Class---->(Class)  |
 *                              ^                |
 *                              |                |
 *                              +----------------+
 *


The following code and output show that the actual inheritance between the
metaclasses (noted between parentheses)  is incorrect :

def inspect_class name, obj
  puts "#################"
  puts "class : #{name} - id : #{obj.object_id}"
  puts "superclass : #{obj.superclass.name} - id : #{
obj.superclass.object_id}" if obj.superclass
  puts "#################"
end

class OtherClass
end

class Object
  inspect_class self.name, self
end

class << Object
  inspect_class "(Object)", self
end

class Module
  inspect_class self.name, self
end

class << Module
  inspect_class "(Module)", self
end

class Class
  inspect_class self.name, self
end

class << Class
  inspect_class "(Class)", self
end

class OtherClass
  inspect_class self.name, self
end

class << OtherClass
  inspect_class "(OtherClass)", self
end

The output :

#################
class : Object - id : 22251190
#################
#################
class : (Object) - id : 22251160
superclass : Class - id : 22251170
#################
#################
class : Module - id : 22251180
superclass : Object - id : 22251190
#################
#################
class : (Module) - id : 22251150
superclass : Class - id : 22251170
#################
#################
class : Class - id : 22251170
superclass : Module - id : 22251180
#################
#################
class : (Class) - id : 22251140
superclass :  - id : 22251140
#################
#################
class : OtherClass - id : 24175280
superclass : Object - id : 22251190
#################
#################
class : (OtherClass) - id : 24175220
superclass :  - id : 22251140
#################

The bugs :

- The superclass of (OtherClass) is (Class) instead of (Object) !

- The superclass of (Class) is (Class) instead of (Module) !

- The superclass of (Module) is (Class) instead of (Object) !



I hope that Matz or another Ruby core developer will see this thread and fix
these bugs.

Chauk-Mean.

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