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

[Jim Rees <jimreesma@x>]

I just use lots of randomness in my generated names.   Collisions will happen, but only once every trillion years or so.

On Mon, Nov 7, 2011 at 6:30 AM, Andy Wingo <wingo@x> wrote:

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

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