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,FREEMAIL_FROM autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,2a34b7ad6c6a0774 X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,UTF8 Path: g2news1.google.com!news4.google.com!feeder.news-service.com!tudelft.nl!txtfeed1.tudelft.nl!zen.net.uk!dedekind.zen.co.uk!aioe.org!not-for-mail From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?= =?utf-8?Q?=29?= Newsgroups: comp.lang.ada Subject: Re: Efficiency of code generated by Ada compilers Date: Sat, 14 Aug 2010 02:02:35 +0200 Organization: Ada At Home Message-ID: References: NNTP-Posting-Host: M2yP1Cx/h9YxW/Ct5b534Q.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes Content-Transfer-Encoding: Quoted-Printable X-Complaints-To: abuse@aioe.org X-Notice: Filtered by postfilter v. 0.8.2 User-Agent: Opera Mail/10.60 (Win32) Xref: g2news1.google.com comp.lang.ada:13256 Date: 2010-08-14T02:02:35+02:00 List-Id: Le Sat, 14 Aug 2010 01:29:56 +0200, a =C3=A9crit: > The Burroughs machines were like that. The descriptor pointing to > an array included the size as well as the base address, so index in-ra= nge > was automatically checked by the hardware. So these old machines were in some way safer than ones of nowadays A similar thing exist with Intel CPUs : memory segment are defined using= a = base and a limit. This may be feasible to assign a memory segment to eac= h = array and then get the same check done (an hardware exception would be = raised if ever an attempt to access a byte beyond the limit was maid), = while this would come with a cost, at least the one to have to switch = memory segment register all the time (this is more costly than reading a= nd = writing any other register). I found a nice page about Burroughs machines and others: http://www.cs.virginia.edu/brochure/museum.html Nice historical document Near the bottom a the page, an photo of a pins labeled =E2=80=9CI touche= d a B5000=E2=80=9D = (which as the page said, was one of these Burroughs machines) If you go down into the page, there is another picture, of an addressabl= e = magnetic tape containing the Nicklaus Wirth's Pascal compiler (touching,= = if I may say so)