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: a07f3367d7,7e8cebf09cf80560 X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII Path: g2news2.google.com!postnews.google.com!i39g2000prd.googlegroups.com!not-for-mail From: KK6GM Newsgroups: comp.lang.ada Subject: Re: How would Ariane 5 have behaved if overflow checking were not turned off? Date: Tue, 15 Mar 2011 12:45:56 -0700 (PDT) Organization: http://groups.google.com Message-ID: <36eecd5e-52fe-4a23-8cbe-7e124c71846d@i39g2000prd.googlegroups.com> References: <82d3lsvqw7.fsf@stephe-leake.org> <87ipvk6vva.fsf@mid.deneb.enyo.de> NNTP-Posting-Host: 12.35.64.226 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1300218356 16713 127.0.0.1 (15 Mar 2011 19:45:56 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Tue, 15 Mar 2011 19:45:56 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: i39g2000prd.googlegroups.com; posting-host=12.35.64.226; posting-account=qZVz2QoAAAAN9WxYp-9jYb7jORc4Zqwt User-Agent: G2/1.0 X-HTTP-Via: 1.1 barracudaweb.tritool.rancho:8080 (http_scan/4.0.2.6.19) X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MDDR; .NET4.0C; .NET4.0E; InfoPath.1),gzip(gfe) Xref: g2news2.google.com comp.lang.ada:19193 Date: 2011-03-15T12:45:56-07:00 List-Id: On Mar 15, 12:12=A0pm, Florian Weimer wrote: > * Stephen Leake: > > > Elias Salom o Helou Neto writes: > > >> I have followed the (quite lenghty) on a topic, IIRC, about bitwise > >> operators, which eventually lead to people mentioning the Ariane 5 > >> case. > > >> Since then I have been wondering. If compiler checking where actually > >> turned on, what would have happened? How could it avoid the disaster? > > > Just to remind people; the real problem was that Ariane 4 code was > > reused on Ariane 5, without carefully considering the design, also > > without adequate testing. > > It's odd that after all those years, little hard data is available on > the defect. =A0The published report uses terminology which is a slightly > bit off in the Ada context, so it led only to further speculation. > There is alleged source code floating around, but it is an obvious > fabrication by someone who is not an Ada programmer (there are syntax > errors). The Ariane computers were based on the MC68020 with MC68882 FPU. "Operand Error", as mentioned in the report, is apparently an FPU error, generated when, among other reasons, a floating point to integer conversion is attempted and the value will not fit into the integer. That's exactly what happened in the Ariane 501. Since the error was apparently a hardware (FPU) trap, that makes it even harder to claim that it was somehow Ada's fault, since presumably all error traps generated by the hardware would have been handled the same regardless of the language.