From: "Mauricio Fernández" <batsman.geo@...>
Date: 2004-06-26T02:19:40+09:00
Subject: Re: Is it considered Harmful?

On Sat, Jun 26, 2004 at 01:35:21AM +0900, Jim Weirich wrote:
> 
> gabriele renzi said:
> > il Fri, 25 Jun 2004 16:51:05 +0200, Michael Walter <cm@leetspeak.org>
> > ha scritto::
> >
> >>Another reason would be that it might be useful to change the object _in
> >>place_. That is, all existing references suddenly point to the new
> >> object.
> >
> > in evil.rb (you can find it at rubyforge) you even have Object#become
> > if you need it ;)
> 
> Are there limitations on evil.rb's implementation of become?  How do you
> get around Guy's concerns about crashing?

evil.rb's Object#become is restricted in several ways, to try to prevent
crashes. Some of the checks include:

* in general, refuse operations that would break implicit assumptions 
in Ruby (memory layout & internal structs):
  * refuse to swap "core classes"
  * refuse to swap modules with non-modules (cause they might be in a
    klass chain)
  * refuse to swap objects whose classes use incompatible "internal types"
  * refuse to operate on immediate values (Fixnum, symbols, true, false, nil...)
* prevent cycles in the klass chains
* check EXIVARs
...

Additionally, the method cache is invalidated after two objects are
swapped.

-- 
Running Debian GNU/Linux Sid (unstable)
batsman dot geo at yahoo dot com

i dont even know if it makes sense at all :) This is an experimental patch
for an experimental kernel :))
	-- Ingo Molnar on linux-kernel