eq and hashing (was Re: [plt-scheme] How to make unit functors?)

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Fri May 30 08:11:05 EDT 2003

At Fri, 30 May 2003 11:04:46 +0200 (CEST), Zbyszek Jurkiewicz wrote:
> On Thu, 29 May 2003, Matthew Flatt wrote:
> > Granted, this is not likely to be much of an issue in the absence of
> > malicious programs. But MzScheme is part of an experiment in protecting
> > against malicious programs.
> Wrong, we cannot protect against malicious programs, otherwise the 
> programming language would become too weak to be useful in practice.

To be clear, I have in mind the kind of protection that Unix provides
against malicious processes. Unix provides a significant level of
protection while remaining useful in practice. :) And I believe we can
achieve an even better balance.

> It is not hard to write a simple program
> which tries to allocate infinite list, practically blocking other
> processes.

That is a problem in the default configuration of PLT Scheme. But if
you configure with --enable-account when building from source, then
it's possible to thwart such attacks using `custodian-limit-memory'.

As the implementation improves, this capability will become available
by default.


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