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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,885dab3998d28a4 X-Google-Attributes: gid103376,public From: Ken Garlington Subject: Re: Ariane 5 failure Date: 1996/10/21 Message-ID: <326BAB1F.BB@lmtas.lmco.com>#1/1 X-Deja-AN: 191038020 references: <96100111162774@psavax.pwfl.com> <32555A39.E38@lmtas.lmco.com> <326506D2.1E40@lmtas.lmco.com> <3267D929.167E@gsde.hso.link.com> content-type: text/plain; charset=us-ascii organization: Lockheed Martin Tactical Aircraft Systems mime-version: 1.0 newsgroups: comp.lang.ada x-mailer: Mozilla 2.02 (Macintosh; I; 68K) Date: 1996-10-21T00:00:00+00:00 List-Id: Samuel T. Harris wrote: > > Keith Thompson wrote: > > > > In <326506D2.1E40@lmtas.lmco.com> Ken Garlington writes: > > [...] > > > Not necessarily. Keep in mind that an exception _was_ raised -- a > > > predefined exception (Operand_Error according to the report). > > > > This is one thing that's confused me about this report. There is no > > predefined exception in Ada called Operand_Error. Either the overflow > > raised Constraint_Error (or Numeric_Error if they were using an Ada > > 83 compiler that doesn't follow AI-00387), or a user-defined exception > > called Operand_Error was raised explicitly. > > > > Remember, the report does NOT state that an unchecked_conversion > was used (as some on this thread have assumed). It only states > a "data conversion from 64-bit floating point to 16-bit signed > integer value". As someone (I forget who) pointed out early > in the thread weeks ago, a standard practice is to scale down > the range of a float value to fit into an integer variable. > This may not have been an unchecked_conversion at all, but > some mathimatical expression. In fact, I would be very surprised if unchecked_conversion was used. It wouldn't make much sense to convert from float to fixed using UC. More than likely, the constraint error/hardware interrupt was raised due to an overflow of the 16-bit value during the type conversion part of the scaling equation. -- LMTAS - "Our Brand Means Quality" For more info, see http://www.lmtas.com or http://www.lmco.com