From: "nobu (Nobuyoshi Nakada)" <nobu@...>
Date: 2013-01-23T16:45:02+09:00
Subject: [ruby-core:51581] [ruby-trunk - Bug #5236][Closed] Including a module in a superclass after it has been included in a subclass leads to infinite recursion if the module uses `super`


Issue #5236 has been updated by nobu (Nobuyoshi Nakada).

Status changed from Assigned to Closed

Already fixed probably at r36595 etc.
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Bug #5236: Including a module in a superclass after it has been included in a subclass leads to infinite recursion if the module uses `super`
https://bugs.ruby-lang.org/issues/5236#change-35540

Author: myronmarston (Myron Marston)
Status: Closed
Priority: Normal
Assignee: nobu (Nobuyoshi Nakada)
Category: 
Target version: 2.0.0
ruby -v: 1.9.x


Under these particular circumstances, you get infinite recursion and a system stack error on 1.9 but not 1.8:

* Create a module that has a method that uses `super`
* Include that module in a class after it has already been included in one of its subclasses
* Instantiate an object of said subclass and call the method

On 1.8, the `super` works as expected.  On 1.9 you get a SystemStackError.  Here's example code that demonstrates the issue:

# example.rb

module MyModule
  def some_method; super; end
end

class MyBaseClass; end

class MySubClass < MyBaseClass;
  include MyModule
end

# To trigger this bug, we must include the module in the base class after
# the module has already been included in the subclass.  If we move this line
# above the subclass declaration, this bug will not occur.
MyBaseClass.send(:include, MyModule)

MySubClass.new.some_method


### The output
��� ruby --version
ruby 1.8.7 (2011-02-18 patchlevel 334) [i686-darwin10.6.0]
��� ruby example.rb 
example.rb:2:in `some_method': super: no superclass method `some_method' for #<MySubClass:0x1001bc2d0> (NoMethodError)
	from example.rb:2:in `some_method'
	from example.rb:13

��� ruby --version
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.6.0]
��� ruby example.rb 
example.rb:2: stack level too deep (SystemStackError)

I've tried it on 1.9.3.preview-1 and I get the SystemStackError there, too.  I would expect 1.9 to act like 1.8 here, and not infinitely recurse on itself.


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