Re: [Scheme-reports] Are generated toplevel definitions secret?

[Andy Wingo <wingo@x>]

Hi,

On Tue 24 May 2011 23:10, Andy Wingo <wingo@x> writes:

>    (define-syntax define-const
>      (syntax-rules ()
>        ((_ name val)
>         (begin
>           (define t val)
>           (define-syntax name (syntax-rules () ((_) t)))))))
>
> Guile currently does not make the generated toplevel definition "t" have
> a fresh name.  It would be nice if it could but it can't be a really
> random name -- it needs to be predictable.
>
> Well why not have the name of "t" be "t" plus some string which depends
> only on the incoming form -- like its hash value.  (Or the outgoing
> form; the considerations are different but similar.)
>
> That way you do preserve the "compatible recompilation" aspect, trading
> off true secrecy, but hey.  Oh well.

FWIW, I have implemented this in Guile's master branch.

  > (define-const foo 10)
  > t-798f2ffcb9d7f9 
  $1 = 10
  > (define-const bar 20)
  > t-
  t-1a0faae6e8559b31  t-798f2ffcb9d7f9    

Here I used tab completion to show me the available bindings.

  > t-1a0faae6e8559b31 
  $2 = 20

The appended uniquifiers are derived from the hash of the stripped
definition form, i.e. `(define t 10)'.  This means that there are still
some situations in which two bindings will collide -- as in:

   (define-syntax define-variable
     (syntax-rules ()
       ((_ name val)
        (begin
          (define t val)
          (define-syntax name
            (syntax-rules ()
              ((_) t)
              ((_ v) (set! t v))))))))

   (define-variable foo 10)
   (define-variable bar 10)
   (bar 20)
   (foo) => 20

I'm not really sure what the right thing is to do here.

Andy
-- 
http://wingolog.org/

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