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=unavailable autolearn_force=no version=3.4.4 Path: border1.nntp.dca3.giganews.com!border2.nntp.dca3.giganews.com!border4.nntp.dca.giganews.com!border2.nntp.dca.giganews.com!nntp.giganews.com!usenet.blueworldhosting.com!feeder02.blueworldhosting.com!reality.xs3.de!news.jacob-sparre.dk!loke.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail From: "Randy Brukardt" Newsgroups: comp.lang.ada Subject: Re: Help with embedded hardware/software platform selection for ADA Date: Tue, 2 Jul 2013 17:47:17 -0500 Organization: Jacob Sparre Andersen Research & Innovation Message-ID: References: <31f9819e-6509-4d67-acea-4d2ba9a96c04@googlegroups.com> <4csim6j63mk4.1c54vo5v7eu8c.dlg@40tude.net> <51d280e7$0$6556$9b4e6d93@newsspool4.arcor-online.net> NNTP-Posting-Host: static-69-95-181-76.mad.choiceone.net X-Trace: loke.gir.dk 1372805237 15283 69.95.181.76 (2 Jul 2013 22:47:17 GMT) X-Complaints-To: news@jacob-sparre.dk NNTP-Posting-Date: Tue, 2 Jul 2013 22:47:17 +0000 (UTC) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-RFC2646: Format=Flowed; Original X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Original-Bytes: 2855 Xref: number.nntp.dca.giganews.com comp.lang.ada:182237 Date: 2013-07-02T17:47:17-05:00 List-Id: wrote in message news:d39ad66d-63a3-43e8-a8ae-3c799c12512e@googlegroups.com... ... >> Why a hobbyist would even look at Ravenscar? >> >Because it provides the simple multitasking that a great many projects can >benefit from. That's true only if you think hobbyists want a lot a frustration. That's because Ravenscar makes it impossible to build resilient systems - the lack of a entry call with timeout means that any error or failure will cause a deadlock. If you are going to use fancy proof tools to *prove* that there are no errors or deadlock possibilities, then this is OK (and that's what Ravenscar is for), but hobbyists are unlikely to have access to such tools. (Heck, *I* have no access to such tools - I'm not even sure if they really exist.) Even if you don't have a sensible recovery action, the timeout can raise an exception pinpointing where the deadlock happened -- which greatly eases debugging. (I don't think Claw would have been usable without that, as it is way too easy to unintentially cause a deadlock by doing the wrong thing in an action handler.) So, IMHO (and much like SPARK), Ravenscar is a tool needed only in very specialized circumstances (typically, some sort of certification requirement). Otherwise, one ought to forget about it and use Ada as it was intended. Randy.