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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: contracted exceptions
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Date: Fri, 8 Jun 2007 20:56:24 +0200
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Date: 2007-06-08T20:56:05+02:00
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On Fri, 08 Jun 2007 20:20:58 +0200, Georg Bauhaus wrote:

> On Fri, 2007-06-08 at 20:00 +0200, Dmitry A. Kazakov wrote: 
>> On Fri, 08 Jun 2007 17:31:05 GMT, Ray Blaak wrote:
> 
>>> Hm. I'm not so sure there is a disagreement as such with fault vs error. I
>>> guess that my point is that what the software does in response to both tends
>>> to be the same: report it and reset/halt/whatever.
>> 
>> Software and more narrowly exceptions cannot report own bugs. It would be a
>> very bad idea to exceptions for that, because vital information about the
>> reasons will be inevitably destroyed. The best possible way is to break
>> into debugger, stopping everything else.
> 
> Or use backtracking and try an alternative path? Which,
> of course, must have be provided, then.

and selected by another program. Debugger is also other program.

> Another option in distributed systems is advertized
> as fault tolerance in the presence of Byzantine faults.
> Uses replicas. Bought by the Redmond machine.

That does not help much with software faults, except the case when the bug
was exposed by some stochastic state. But even then, if you try a replica
on the exactly same state, then it will fail again. If you continue it from
a different state, then it won't be really 100% recovering or a replica.
Redundant systems are good for dealing with hardware faults. Well-paid Ada
programmers for preventing software ones (:-)).

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de