From: Christoph <chr_news@...>
Date: 2002-09-04T02:58:49+09:00
Subject: Allocate crash loop hole.

Hi,

Ruby's current (admittedly pointless) ability to instantiate
``higher order'' meta classes bunches a hole in the new 
defenses around the allocate frame work. The following script
segfaults on ruby 1.7.3 (2002-08-29) [i386-mswin32]. (Also see 
[ruby-talk: 38612]).  Maybe this is a good enough reason to 
to identify Class and Object.meta(1)? 


---
class Object
  def meta(n)
    n.zero? ? self : \
      class << self; self end.meta(n-1) 
  end
end

Odd  = 19 
Even = 12

CrashClass = Class.meta(Odd).allocate
Class.meta(Even).allocate rescue puts "bad" # bad

CrashClass.allocate rescue puts "bad"       # bad
p CrashClass.type                           # Class
p CrashClass.superclass                     # nil 

# CrashClass can instantiate working classes - weird!
A = CrashClass.new
B = CrashClass.new

class A
  def okay;  'okay' end
end

p  A.superclass == Object    # true
p  A == B                    # false
p  A.new.okay                # okay


def CrashClass.okay20; p 'fine' end  

A.meta(18).okay20  rescue p 'bad' # bad
A.meta(21).okay20  rescue p 'bad' # bad
A.meta(30).okay20                 # fine


begin
  class CrashClass
  end
rescue TypeError => mes
  p mes #<TypeError: CrashClass is not a class>
end
  
# however this will crash

CrashClass.class_eval {
  def crash; end
}
---

/Christoph