[racket-dev] Separate Compilation Vulnerable to FFI... what to do?

I'm not sure I follow. When you use unsafe features, you can defeat
most any intended invariant; that's what makes them "unsafe", right?

Whether this particular example is ok depends on what you want
`unsafe-global` to mean. If you want it to correspond to external state
--- such as a filesystem or a remote process --- then it is implemented
ok. Otherwise, I agree that the implementation of `unsafe-global` is
bad.

If you count the behavior as bad, then you're right that fixing it up
means using similar unsafe functionality. Specifically, the
scheme_register_process_global() function (accessible only via
`ffi/unsafe`) helps to implement state that spans instantiations and
places.

At Tue, 29 Apr 2014 06:10:19 -0600, Jay McCarthy wrote:
> If you look at this directory:
> 
> https://github.com/jeapostrophe/exp/tree/master/fffhase-attack
> 
> There's a short "attack" on the promise that different instantiations
> of the same module across phases don't share a store.
> 
> Running without compiled version
> rm -fr compiled
> racket -t phase0.rkt --
> static: unsafe-global was 0
> static: safe-global was 0
> dynamic: unsafe-global is 1
> dynamic: safe-global is 0
> 
> Running with compiled version
> raco make phase0.rkt
> racket -t phase0.rkt --
> static: unsafe-global was 0
> static: safe-global was 0
> dynamic: unsafe-global is 0
> dynamic: safe-global is 0
> 
> Should we consider this fine because the effect is "external" (just
> like touching a file) or should there be a generalization of the
> racket/gui/base rule that the module can't be instantiated multiple
> times?
> 
> A bit of a grep doesn't lead to any easy place where that is
> implemented.... it seems like that feature can only be implemented
> with a restricted form of the attack itself, so you can observe that
> the instantiation already happened.
> 
> Jay
> 
> -- 
> Jay McCarthy <jay at cs.byu.edu>
> Assistant Professor / Brigham Young University
> http://faculty.cs.byu.edu/~jay
> 
> "The glory of God is Intelligence" - D&C 93