From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: a07f3367d7,f096ebb5dcac664d X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news4.google.com!feeder.news-service.com!feeder.news-service.com!cyclone01.ams2.highwinds-media.com!news.highwinds-media.com!npeersf01.ams.highwinds-media.com!newsfe28.ams2.POSTED!7564ea0f!not-for-mail From: John McCabe Newsgroups: comp.lang.ada Subject: Re: Ariane 5 Failure from 1996 Message-ID: <4n1f5510eum9c0b53rb1ui111rmgf23fgd@4ax.com> References: <14e1cf5c-b053-49ec-83c8-d36b9afc49ab@p29g2000yqh.googlegroups.com> X-Newsreader: Forte Agent 2.0/32.652 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 80.176.146.77 X-Complaints-To: abuse@demon.net X-Trace: newsfe28.ams2 1247250559 80.176.146.77 (Fri, 10 Jul 2009 18:29:19 UTC) NNTP-Posting-Date: Fri, 10 Jul 2009 18:29:19 UTC Date: Fri, 10 Jul 2009 19:29:13 +0100 Xref: g2news2.google.com comp.lang.ada:6954 Date: 2009-07-10T19:29:13+01:00 List-Id: jonathan wrote: Jonathan >Any program that met the requirements would have destroyed the flight >at exactly the same time and in exactly the same way. It could >have been written in C, Ada, or assembly and if it met the >requirements >exactly it would have destroyed flight 501 the same 37 seconds >after liftoff. > >Post-flight analysis described the problem as a requirements failure . > >(That's my memory of the event.) I don't want to get into another discussion on the failure itself, I'd just like to know if there's any known information about this claim that's been made about C. FWIW though, if, as someone else has said, the SRI for A5 used a MIL-STD-1750A processor then, as I remember that chip, there is a way for arithmetic overflow (i.e. x + y = z where x and y are both positive and z is negative) to cause a machine fault interrupt. I imagine that this would be disabled in C as it's not a check that should be made by the language (forgive me if my memory of MIL-STD-1750A is hazy, I haven't used them since 1997). The point this guy was making was that, in C, the machine fault would not have occured as the overflow would have been allowed to happen and 3 or 4 seconds later the SRI would have shut down as expected (well, as required for Ariane 4!) and all would have been well. Sounds like nonsense to me though. John