Re: The problem with stack-based environments...

[joao lobato <btnfdp.lobato@...>]

Lua provides mechanisms, you write the modules.

Couldn't you wrap every method of your plugin such that

  plugin:method()

would actually do

  local results
  local table = table
  in sandbox do
      results = table.pack(plugin:method())
  end
  return table.unpack(results,1,results.n)

(using proxy tables with __index functions)?

On 1/31/10, Mark Hamburg <mark@grubmah.com> wrote:
> As the primary proponent of stack-based-environments -- though I will
> identify myself less as a proponent and more as someone who has tried get
> clarity around what in-do-end seems to be implying (as opposed to what it
> actually does) -- I need to call out the biggest problem that's occurred to
> me with them:
>
> While sandboxing itself is easy:
>
> 	in sandbox do
> 		sandboxed_function()
> 	end
>
> If the sandbox generates an object or a callback for later use:
>
> 	local plugin
> 	in sandbox do
> 		plugin = plugin_loader()
> 	end
>
> We need to decide what to do when we later invoke a method on the object or
> invoke the callback. A straight call as in:
>
> 	plugin:method()
>
> will not get sandboxed. We can certainly wrap it up in an appropriate
> sandboxing construct, but that's going to be a pain to remember to do and
> its going to be awkward in places where we want to work with the results of
> the method call since in-do-end is not an expression.
>
> Furthermore, we may not want it always wrapped. If we are exploiting the
> stack-based environments for i/o redirection, for example -- a standard use
> case -- then we probably want that redirection preserved into the method
> call.
>
> I don't have a proposed resolution at this time that would resolve this
> tension.
>
> Mark
>
>