From: "Mauricio Fernández" <batsman.geo@...>
Date: 2003-02-05T08:11:50+09:00
Subject: Re: [contest] Code challenge

On Wed, Feb 05, 2003 at 07:31:49AM +0900, Paul Brannan wrote:
> On Wed, Feb 05, 2003 at 06:00:43AM +0900, Mauricio Fern�ndez wrote:
> > But now, what happens if I do:
> > 
> > ...
> >   def no_redef(*args)
> >     @no_override ||= []
> >     args.each { |i| @no_override << i }
> >     @no_override.freeze
> >   end
> > ...
> > 
> > Is it impossible enough now? ;-) 
> 
> Not quite.  Here are my 5 solutions:

Ouch!
 
> # Solution 1: Redefine Array#+
...
> # Solution 2: Redefine Array#index
...
> # Solution 3: Redefine Fixnum#==
...
> # Solution 4: Use alias_method to create an alias for alias_method so
> # that I can still create aliases in the derived class.

I guess I'd have to freeze _everything_ I use inside NoOverloading to
prevent these and modify alias_method on Module...
Another possibility is implementing my own cheap Array class. 

> # Solution 5: Use set_trace_func to capture all bindings; use this so
> # that any method that any calls __no_redef_list__ are equivalent to
> # "return".

And remove Kernel.set_trace_func.
 
> 
> > My ultimate goal with this contest is seeing if it is at all possible to
> > prevent redefinition unconditionally, against all attacks. 
> 
> My suspicion is that this is not possible without modifying the
> interpreter.  I also suspect that protecting against all "attacks" is
> unnecessary, and that protecting the programmer against shooting himself
> in the foot is sufficient.

Was rather thinking of another way to do Rubyrobots without using safe
levels, that's all.

At least I learned something in the process, and first thing: forget
about doing code contests for some time until I know quite a lot more ;)

I'll keep "closing holes" on the Wiki in case anybody is interested on
seeing if this will ever work.

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batsman dot geo at yahoo dot com

> Alan Cox wrote:
[..]

No I didnt.  Someone else wrote that.  Please keep attributions
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