[plt-dev] certificates, #%module-begin, and typed-scheme's soundness

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Wed Dec 16 23:36:53 EST 2009

Hard to tell without looking at how typed scheme's macros work tho.


On Wednesday, December 16, 2009, Sam TH <samth at ccs.neu.edu> wrote:
> On Wed, Dec 16, 2009 at 6:05 PM, Carl Eastlund <carl.eastlund at gmail.com> wrote:
>> On Wed, Dec 16, 2009 at 5:19 PM, Sam TH <samth at ccs.neu.edu> wrote:
>>> The program at the end of this message behaves in arbitrary ways.  In
>>> particular, it segfaults on my system.  However, this should be safe:
>>> Typed Scheme is checking that only vectors are passed to `f'.  But the
>>> `cheater' macro uses `local-expand' to extract a reference to `f', and
>>> use it in arbitrary ways.
>> You provided 'f'.  Certificates do not protect identifiers that are
>> provided from the module that defines them.
> As Jay points out, I didn't really provide `f'.  I provided a
> rename-transformer that points to `f'.  Here's a more explicit version
> of the original module:
> (module m typed/scheme
>   (require scheme/unsafe/ops (for-syntax scheme/base))
>   (: f ((Vectorof (U)) -> Any))
>   (define (f x) (unsafe-vector-length x))
>   (define-syntax f*
>     (make-rename-transformer #'f))
>   (provide (rename-out [f* f])))
> This suggests to me that this is a bug in the interaction of
> rename-transformers and certificates.
> --
> sam th
> samth at ccs.neu.edu
> _________________________________________________
>   For list-related administrative tasks:
>   http://list.cs.brown.edu/mailman/listinfo/plt-dev

Posted on the dev mailing list.