From: ara.t.howard@...
Date: 2005-12-08T12:40:23+09:00
Subject: Re: code execution from file?

On Thu, 8 Dec 2005, ako... wrote:

> thank you very much for your help.
>
> my application runs inside a web browser process, and creating a thread does
> not seem scalable.


but what if the user code creates one?  it's the only way to isolate $SAFE and
your vars, see below...


> i tried to evaluate a file from inside a lambda and it seems to work. i also
> was able to set safety level for lambda locally which effectively restores
> $SAFE when lambda finishes. the only drawback of this was that my
> environment is still visible from lambdas.


also note that lambda will prevent __everything__ in it's scope from __ever__
being garbage collected.  this is bad idea in a web app - assuming it's
persistant like fastcgi.


in any case be careful:

     harp:~ > cat a.rb
     code = IO::read "b.rb"

     p = eval <<LAMBDA
        lambda {
        module Mod
        $SAFE = 3
        #{code}
        end
        }
     LAMBDA

     p.call
     p "we won't see this!"


     harp:~ > cat b.rb
     exit!


     harp:~ > ruby a.rb


a thread will prevent you main program from exiting.


regards.

-a
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