Re: Arithmetic overflow checking

From	Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups	comp.lang.java.programmer, comp.lang.c
Subject	Re: Arithmetic overflow checking
Date	2011-08-13 21:54 +0300
Organization	Tidorum Ltd
Message-ID	<9anviiF606U1@mid.individual.net> (permalink)
References	(6 earlier) <36bp17tf79bhbd6hovf9srhmcs1jh1c040@4ax.com> <ivid4r$34o$1@localhost.localdomain> <693db00d-83be-4830-a1fc-262d9d34d672@z15g2000pre.googlegroups.com> <naip179apc4bmtnmlm3mb6t3ru9o179qi0@4ax.com> <9d33ce51-1f6a-4782-8098-a051456532ca@m6g2000prh.googlegroups.com>

Cross-posted to 2 groups.

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lewbloch wrote:
> Gene Wirchenko wrote:
>> lewbloch wrote:
>>> Martin Gregorie wrote:
>> [snip]
>>
>>>> [1] The instrument causing the problem was an unmodified Ariane 4 SRI
>>>> which raised an out-of-limits exception when the normal Ariane 5
>>>> trajectory exceeded a permitted Ariane 4 horizontal velocity limit.  
>>      ...the Ariane 5 having more powerful engines.
>>
>>> In other words, this was a case where there *was* an out-of-range
>>> exception, thus it makes the exact opposite point to the one Gene
>>> presumably wanted to support.
>>      The data I read was that the exception was not handled.  IIRC,
>> debugging got interpreted as navigational data.
>>
> 
> Precisely.  There was an exception, and it was not handled.  Having
> the exception was not enough.

There was an exception (overflow in a conversion instruction), and it 
was handled. However, the handler was designed for the Ariane 4, where 
the designers (after careful analysis of the data ranges for the Ariane 
4) decided to assume that an overflow exception indicated a CPU HW 
failure, and consequently the handler shut down the CPU. The same 
overflow then occurred in the redundant CPU, which also shut down, so 
the rocket was left with no guidance.

If the SW had been tested properly, the overflow exception would have 
occurred during testing, which would have revealed the flawed 
assumptions made in the reuse of the Ariane 4 SW on the Ariane 5. Surely 
that would have been better than ignoring the overflow.

The Ariane 501 disaster is a poor guide for this discussion, because of 
the difficulty of proper exception handling in that system: you cannot 
abort the launch and return to the launch pad. In most applications, it 
is much easier to design reasonable and safe exception handlers.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .

Thread

Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-10 01:47 -0700
  Re: Arithmetic overflow checking China Blue Dolls <chine.bleu@yahoo.com> - 2011-07-10 02:47 -0700
    Re: Arithmetic overflow checking pete <pfiland@mindspring.com> - 2011-07-10 06:04 -0400
      Re: Arithmetic overflow checking China Blue Dolls <chine.bleu@yahoo.com> - 2011-07-10 03:29 -0700
        Re: Arithmetic overflow checking Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-07-10 20:52 +0300
        Re: Arithmetic overflow checking pete <pfiland@mindspring.com> - 2011-07-10 23:29 -0400
    Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-10 04:44 -0700
      Re: Arithmetic overflow checking "BartC" <bc@freeuk.com> - 2011-07-12 11:33 +0100
        Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 04:17 -0700
          Re: Arithmetic overflow checking "BartC" <bc@freeuk.com> - 2011-07-12 12:33 +0100
            Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 05:24 -0700
              Re: Arithmetic overflow checking Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-12 21:45 -0400
          Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-12 05:25 -0700
            Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 10:21 -0700
              Re: Arithmetic overflow checking Thomas Boell <tboell@domain.invalid> - 2011-07-12 22:39 +0200
                Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 14:15 -0700
                Re: Arithmetic overflow checking Keith Thompson <kst-u@mib.org> - 2011-07-12 14:18 -0700
                Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 23:54 -0700
            Re: Arithmetic overflow checking "BartC" <bc@freeuk.com> - 2011-07-12 19:14 +0100
              Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-13 00:20 -0700
        Re: Arithmetic overflow checking markspace <-@.> - 2011-07-12 09:26 -0700
          Re: Arithmetic overflow checking Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-12 10:52 -0600
            Re: Arithmetic overflow checking Keith Thompson <kst-u@mib.org> - 2011-07-12 10:48 -0700
              Re: Arithmetic overflow checking Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-12 12:36 -0600
                Re: Arithmetic overflow checking Keith Thompson <kst-u@mib.org> - 2011-07-12 12:16 -0700
                Re: Arithmetic overflow checking Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-12 14:09 -0600
                Re: Arithmetic overflow checking Keith Thompson <kst-u@mib.org> - 2011-07-12 14:16 -0700
              Re: Arithmetic overflow checking, not so hard after all "Greg A. Woods" <woods@robohack.org> - 2011-07-12 21:52 -0700
                Re: Arithmetic overflow checking, not so hard after all Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-13 12:50 +0100
                Re: Arithmetic overflow checking, not so hard after all "Greg A. Woods" <woods@robohack.org> - 2011-07-13 11:10 -0700
                Re: Arithmetic overflow checking, not so hard after all Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-07-14 01:34 +0100
                Re: Arithmetic overflow checking, not so hard after all "Greg A. Woods" <woods@robohack.org> - 2011-07-19 17:10 -0700
                Re: Arithmetic overflow checking, not so hard after all Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-07-19 20:47 -0600
                Re: Arithmetic overflow checking, not so hard after all Keith Thompson <kst-u@mib.org> - 2011-07-19 20:23 -0700
                Re: Arithmetic overflow checking, not so hard after all "Greg A. Woods" <woods@robohack.org> - 2011-09-06 17:47 -0700
                Re: Arithmetic overflow checking, not so hard after all Todd Carnes <toddcarnes@gmail.com> - 2011-07-20 03:48 +0000
                Re: Arithmetic overflow checking, not so hard after all Keith Thompson <kst-u@mib.org> - 2011-07-13 09:27 -0700
              Re: Arithmetic overflow checking "MikeP" <mp011011@some.org> - 2011-07-14 23:55 -0500
          Re: Arithmetic overflow checking Martin Gregorie <martin@address-in-sig.invalid> - 2011-07-12 16:54 +0000
            Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-12 11:35 -0700
          Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 10:13 -0700
          Re: Arithmetic overflow checking Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-12 21:53 -0400
        Re: Arithmetic overflow checking "MikeP" <mp011011@some.org> - 2011-07-14 23:41 -0500
          Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-15 10:56 -0700
            Re: Arithmetic overflow checking "MikeP" <mp011011@some.org> - 2011-07-15 21:27 -0500
      Re: Arithmetic overflow checking bugbear <bugbear@trim_papermule.co.uk_trim> - 2011-07-20 09:22 +0100
        Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-20 10:51 -0700
          Re: Arithmetic overflow checking gordonb.3urm7@burditt.org (Gordon Burditt) - 2011-07-20 15:39 -0500
          Re: Arithmetic overflow checking "BartC" <bc@freeuk.com> - 2011-07-21 12:12 +0100
    Re: Arithmetic overflow checking Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-10 09:28 -0400
      Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-10 06:52 -0700
        Re: Arithmetic overflow checking Keith Thompson <kst-u@mib.org> - 2011-07-10 14:47 -0700
        Re: Arithmetic overflow checking gordonb.u8vng@burditt.org (Gordon Burditt) - 2011-07-11 18:45 -0500
      Re: Arithmetic overflow checking "MikeP" <mp011011@some.org> - 2011-07-14 23:07 -0500
    Re: Arithmetic overflow checking Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-07-10 12:25 -0400
  Re: Arithmetic overflow checking Robert Wessel <robertwessel2@yahoo.com> - 2011-07-10 10:47 -0500
  Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-11 07:58 -0700
    Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-11 10:48 -0700
      Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-11 14:40 -0700
    Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-11 14:54 -0700
      Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-11 15:55 -0700
      Re: Arithmetic overflow checking Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-11 21:51 -0400
        Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-11 21:31 -0700
          Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-11 23:16 -0700
          Re: Arithmetic overflow checking James Kuyper <jameskuyper@verizon.net> - 2011-07-12 06:28 -0400
          Re: Arithmetic overflow checking David Thompson <dave.thompson2@verizon.net> - 2011-07-24 22:13 -0400
            Re: Arithmetic overflow checking Lew Pitcher <lpitcher@teksavvy.com> - 2011-07-25 10:24 -0400
  Re: Arithmetic overflow checking "io_x" <a@b.c.invalid> - 2011-07-12 09:05 +0200
    Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 02:22 -0700
      Re: Arithmetic overflow checking "io_x" <a@b.c.invalid> - 2011-07-12 11:34 +0200
        Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-12 03:04 -0700
          Re: Arithmetic overflow checking "Greg A. Woods" <woods@robohack.org> - 2011-07-12 19:55 -0700
            Re: Arithmetic overflow checking "Greg A. Woods" <woods@robohack.org> - 2011-07-12 21:54 -0700
            Re: Arithmetic overflow checking "MikeP" <mp011011@some.org> - 2011-07-14 23:28 -0500
              Re: Arithmetic overflow checking "Greg A. Woods" <woods@robohack.org> - 2011-07-19 17:16 -0700
        Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-12 03:33 -0700
        Re: Arithmetic overflow checking David Lamb <dalamb@cs.queensu.ca> - 2011-07-12 08:29 -0400
      Re: Arithmetic overflow checking "io_x" <a@b.c.invalid> - 2011-07-12 13:18 +0200
      Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-12 11:39 -0700
        Re: Arithmetic overflow checking Patricia Shanahan <pats@acm.org> - 2011-07-12 12:38 -0700
          Re: Arithmetic overflow checking markspace <-@.> - 2011-07-12 13:20 -0700
            Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-12 13:23 -0700
              Re: Arithmetic overflow checking Martin Gregorie <martin@address-in-sig.invalid> - 2011-07-12 21:08 +0000
                Re: Arithmetic overflow checking lewbloch <lewbloch@gmail.com> - 2011-07-12 14:48 -0700
                Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-12 15:24 -0700
                Re: Arithmetic overflow checking lewbloch <lewbloch@gmail.com> - 2011-07-12 16:09 -0700
                Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-13 10:38 -0700
                Re: Arithmetic overflow checking Patricia Shanahan <pats@acm.org> - 2011-07-13 11:00 -0700
                Re: Arithmetic overflow checking lewbloch <lewbloch@gmail.com> - 2011-07-13 12:16 -0700
                Re: Arithmetic overflow checking Gene Wirchenko <genew@ocis.net> - 2011-07-13 13:10 -0700
                Re: Arithmetic overflow checking markspace <-@.> - 2011-07-13 13:21 -0700
                Re: Arithmetic overflow checking Keith Thompson <kst-u@mib.org> - 2011-07-13 13:41 -0700
                Re: Arithmetic overflow checking Robert Wessel <robertwessel2@yahoo.com> - 2011-07-14 21:10 -0500
                Re: Arithmetic overflow checking "io_x" <a@b.c.invalid> - 2011-07-15 11:57 +0200
                Re: Arithmetic overflow checking Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-07-15 04:36 -0700
                Re: Arithmetic overflow checking Niklas Holsti <niklas.holsti@tidorum.invalid> - 2011-08-13 21:54 +0300
      Re: Arithmetic overflow checking "Greg A. Woods" <woods@robohack.org> - 2011-07-12 20:03 -0700
        Re: Arithmetic overflow checking tm <thomas.mertes@gmx.at> - 2011-07-13 00:52 -0700
          Re: Arithmetic overflow checking Patricia Shanahan <pats@acm.org> - 2011-07-13 07:45 -0700
            Re: Arithmetic overflow checking "Greg A. Woods" <woods@robohack.org> - 2011-07-13 11:28 -0700
          Re: Arithmetic overflow checking "Greg A. Woods" <woods@robohack.org> - 2011-07-13 11:15 -0700

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