From owner-sc22wg5+sc22wg5-dom8=www.open-std.org@open-std.org Wed Jan 16 23:34:11 2013 Return-Path: X-Original-To: sc22wg5-dom8 Delivered-To: sc22wg5-dom8@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id 22E76356C84; Wed, 16 Jan 2013 23:34:11 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from ppsw-43.csi.cam.ac.uk (ppsw-43.csi.cam.ac.uk [131.111.8.143]) by www.open-std.org (Postfix) with ESMTP id 3D7B0356944 for ; Wed, 16 Jan 2013 23:34:09 +0100 (CET) X-Cam-AntiVirus: no malware found X-Cam-SpamDetails: not scanned X-Cam-ScannerInfo: http://www.ucs.cam.ac.uk/email/scanner/ Received: from hermes-1.csi.cam.ac.uk ([131.111.8.51]:45542) by ppsw-43.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.159]:25) with esmtpa (EXTERNAL:nmm1) id 1TvZhw-00039F-nA (Exim 4.72) (return-path ); Wed, 16 Jan 2013 20:35:36 +0000 Received: from prayer by hermes-1.csi.cam.ac.uk (hermes.cam.ac.uk) with local (PRAYER:nmm1) id 1TvZhw-0001lf-74 (Exim 4.72) (return-path ); Wed, 16 Jan 2013 20:35:36 +0000 Received: from [87.114.176.251] by webmail.hermes.cam.ac.uk with HTTP (Prayer-1.3.5); 16 Jan 2013 20:35:36 +0000 Date: 16 Jan 2013 20:35:36 +0000 From: "N.M. Maclaren" To: longb@cray.com Cc: sc22wg5 Subject: Re: [ukfortran] (SC22WG5.4899) (j3.2006) Comment on a comment on the WG5 letterballot on N1947 Message-ID: In-Reply-To: <20130116191114.A6A75356A2B@www.open-std.org> References: <20130108205438.50F4E356B56@www.open-std.org> <20130113210632.B1C67356BEA@www.open-std.org> <20130116050422.92E30356BE0@www.open-std.org> <20130116191114.A6A75356A2B@www.open-std.org> X-Mailer: Prayer v1.3.5 Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Sender: owner-sc22wg5@open-std.org Precedence: bulk On Jan 16 2013, Bill Long wrote: > >In recent memory, I've only encountered one case of harmful integer >overflow, and that occurred in converting a large real value to integer >and was caught by the IEEE hardware traps. Of course, there are >numerous cases, almost all related to user-written random number >generators, where overflow of integer multiply is intentional. For >those cases, enabling a check would cause the program to stop working. Do none of the codes you see ever include fragments like the following? SUBROUTINE weeble (arg) REAL(KIND=KIND(0.0D0)) :: arg(:,:) REAL(KIND=KIND(0.0D0)) :: scratch(UBOUND(arg,1)*(UBOUND(arg,1)+1)/2) Being caught out by default integers being large enough for any single dimension but not the total size of an array, and accidentally using a calculation that creates the latter, is a very common mistake in all of Fortran, C and C++. Regards, Nick Maclaren.