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From: nmm1@cus.cam.ac.uk (Nick Maclaren)
Newsgroups: comp.arch,comp.lang.ada
Subject: Re: Language support for  flexible handling of system-detected
 errors.
Date: 8 Apr 2002 18:10:28 GMT
Organization: University of Cambridge, England
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 <a8h129$cr6$02$1@news.t-online.com> <a8hqrv$r83$1@nh.pace.co.uk>
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Date: 2002-04-08T18:10:28+00:00
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In article <ba162549.0204080917.7da8068b@posting.google.com>,
Kevin Cline <kcline17@hotmail.com> wrote:
>"Marin David Condic" <dont.bother.mcondic.auntie.spam@[acm.org> wrote in message news:<a8hqrv$r83$1@nh.pace.co.uk>...
>> What makes you think that there are any 100% error free Ada compilers out
>> there? :-) Its impossible to prove that there are no errors in a compiler or
>> any other sufficiently complex piece of software. And yes, I've encountered
>> errors in every Ada compiler I've ever used. It might be the case that Ada
>> compilers - having run through validation - at least fully implement the
>> language and do so in a consistent way. 
>
>I wouldn't count on that either.  Validation suites may be incomplete,
>particularly for a very large language like Ada.
>
>I found bugs in two validated Ada-83 compilers within a month after
>I started using them.

Validation suites are provably impossible to make bulletproof for
any language powerful enough to implement a Turing machine, which
includes any useful general-purpose language.


Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email:  nmm1@cam.ac.uk
Tel.:  +44 1223 334761    Fax:  +44 1223 334679