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[Python-Dev] Sandboxing Python

Steven D'Aprano steve at pearwood.info
Sun Mar 4 23:53:48 CET 2012 
Armin Rigo wrote:
> Hi Mark,
> 
> On Sun, Mar 4, 2012 at 18:34, Mark Shannon <mark at hotpy.org> wrote:
>> You can't solve the too much time, without solving the halting problem,
> 
> Not sure what you mean by that.  It seems to me that it's particularly
> easy to do in a roughly portable way, with alarm() for example on all
> UNIXes.

What time should you set the alarm for? How much time is enough before you 
decide that a piece of code is taking too long?

The halting problem is not that you can't breaking out of an infinite loop, 
but that you can't *in general* decide when you are in an infinite loop.

I think that Mark's point is that you can't, in general, tell when you are in 
a "too much time" attack (or bug) that needs to be broken out of rather than 
just a legitimately long calculation which will terminate if you wait just a 
little longer.


-- 
Steven
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