[racket] Handin Server + PLAI problem [and 1 more messages] [and 2 more messages]

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Sun Jan 15 18:42:05 EST 2012

On Sun, Jan 15, 2012 at 5:00 PM, John Clements
<clements at brinckerhoff.org> wrote:
> On Jan 14, 2012, at 8:19 PM, Robby Findler wrote:
>> Perhaps the right thing is to have the setup code export a small
>> library that contains a "is my mark bound in the context" function and
>> then the sandbox can call that function when deciding whether or not
>> to grant permission.
>> (That has the dependencies going the right way, right?)
>> It doesn't get us really any steps closer to the more general solution
>> but perhaps it is enough for this discussion to end?
> Attempting clarification and summary:
> The access violation is caused indirectly by a call to variable-name->module-source (sp?), and the offending call to "exists?" is located in main-collects.rkt, which ought to be entitled to check whether files exist.
> (It's not clear to me while main-collects needs to check this, but I'm not going to worry about this.)
> The short-term solution is simply to disable the contract wrapper on print-only-errors... and presumably on the other parameters? I'm in the dark still about which kinds of contracts and/or contract uses trigger the offending use of variable-name->module-source (sp).

I'm not sure either (this is certainly not the only contract that's
checked during the execution of PLAI programs, but maybe it's the only
provide/contract one?), but once I disabled that, my sample solution
for the next exercise went through.

It would be good to know how to get a better short-term solution,
however (like making a more relaxed sandbox that allows exists queries
in the handin server).


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