From owner-sc22wg5@open-std.org Fri Nov 14 03:10:49 2008 Return-Path: X-Original-To: sc22wg5-dom7 Delivered-To: sc22wg5-dom7@www2.open-std.org Received: by www2.open-std.org (Postfix, from userid 521) id 4A761CA5FE5; Fri, 14 Nov 2008 03:10:49 +0100 (CET) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from sca-es-mail-2.sun.com (sca-es-mail-2.Sun.COM [192.18.43.133]) by www2.open-std.org (Postfix) with ESMTP id 5EBDFC178D6 for ; Fri, 14 Nov 2008 03:10:47 +0100 (CET) Received: from fe-sfbay-09.sun.com ([192.18.43.129]) by sca-es-mail-2.sun.com (8.13.7+Sun/8.12.9) with ESMTP id mAE2Ad66009216 for ; Thu, 13 Nov 2008 18:10:42 -0800 (PST) Received: from conversion-daemon.fe-sfbay-09.sun.com by fe-sfbay-09.sun.com (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) id <0KAA00B01WK6W300@fe-sfbay-09.sun.com> (original mail from Robert.Corbett@Sun.COM) for sc22wg5@open-std.org; Thu, 13 Nov 2008 18:10:39 -0800 (PST) Received: from [129.146.84.104] by fe-sfbay-09.sun.com (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) with ESMTPSA id <0KAA00313WPO7W40@fe-sfbay-09.sun.com>; Thu, 13 Nov 2008 18:10:37 -0800 (PST) Date: Thu, 13 Nov 2008 18:10:36 -0800 From: Robert Corbett Subject: Re: (j3.2006) (SC22WG5.3673) [ukfortran] N1755: Request for new features from MPI Forum In-reply-to: <491CD5CB.4030003@cray.com> To: longb@cray.com Cc: WG5 Reply-To: Robert.Corbett@Sun.COM Message-id: <491CDE1C.8050003@sun.com> Organization: Sun Microsystems, Inc. MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=us-ascii Content-transfer-encoding: 7BIT X-Accept-Language: en-us, en References: <49137AD3.1070402@lrz.de> <20081111224927.8201CC178D9@www2.open-std.org> <20081111234923.517C5C178D6@www2.open-std.org> <20081112001017.26EB3C178D6@www2.open-std.org> <20081112091351.6581CC178D9@www2.open-std.org> <491BCB6F.8040406@sun.com> <20081113072205.9063AC178D9@www2.open-std.org> <491BDF12.8050108@sun.com> <491CD5CB.4030003@cray.com> User-Agent: Mozilla/5.0 (X11; U; SunOS sun4u; en-US; rv:1.7.13) Gecko/20060509 Sender: owner-sc22wg5@open-std.org Precedence: bulk Bill Long wrote: > > > Robert Corbett wrote: > >> The committe might have intended PROTECTED to be something other than >> a promise made by the programmer, but the standard as written makes it >> exactly that. Just because INTENT(IN) has a similar defect does not >> make it any the less true. >> >> The standard as written allows a compiler to assume that a variable >> that has the PROTECTED attribute is not definable outside the module, >> but it allows programs to be written that define the variable outside >> of the module and it does not require the processor to detect the error. >> If a programmer writes a program that defines the variable outside the >> module, it is not a standard-conforming program, and so a >> standard-conforming processor is free to do anything whatever when >> compiling or executing the program. The onus is on the programmer to >> avoid defining the variable outside the module. > > The first sentence says the standard allows a programmer to do X. The > second one seems to say that IF the programmer does X, the program is > not standard conforming. That seems a bit contradictory. I shall attempt to state it more clearly. Programs can be written that are not standard-conforming, but a compiler cannot practically detect that they are not standard conforming. In particular, violations of the restrictions imposed on deinition of a variable with the PROTECTED attribute cannot be detected in all cases. Thus, the standard effectively requires a processor to successfully compile programs that are not standard conforming to avoid rejecting some programs that are standard conforming. I can easily imagine a scheme for detecting abuse of variables with the PROTECTED attribute at run-time, but only at a prohibitive cost. Bob Corbett