From owner-sc22wg5@open-std.org Thu Jun 11 21:21:55 2009 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 097CCC76BB7; Thu, 11 Jun 2009 21:21:55 +0200 (CET DST) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from ppsw-5.csi.cam.ac.uk (ppsw-5.csi.cam.ac.uk [131.111.8.135]) by www2.open-std.org (Postfix) with ESMTP id 2D459C4596B for ; Thu, 11 Jun 2009 21:21:29 +0200 (CET DST) X-Cam-AntiVirus: no malware found X-Cam-SpamDetails: not scanned X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ Received: from hermes-2.csi.cam.ac.uk ([131.111.8.54]:47611) by ppsw-5.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.155]:25) with esmtpa (EXTERNAL:nmm1) id 1MEpq5-0004lL-HG (Exim 4.70) for sc22wg5@open-std.org (return-path ); Thu, 11 Jun 2009 20:21:29 +0100 Received: from prayer by hermes-2.csi.cam.ac.uk (hermes.cam.ac.uk) with local (PRAYER:nmm1) id 1MEpq5-0004Zw-Am (Exim 4.67) for sc22wg5@open-std.org (return-path ); Thu, 11 Jun 2009 20:21:29 +0100 Received: from [83.67.89.123] by webmail.hermes.cam.ac.uk with HTTP (Prayer-1.3.1); 11 Jun 2009 20:21:29 +0100 Date: 11 Jun 2009 20:21:29 +0100 From: "N.M. Maclaren" To: sc22wg5@open-std.org Subject: Re: [ukfortran] (SC22WG5.4006) (j3.2006) NOT on Paper 09-238 Message-ID: In-Reply-To: <20090611182420.3A14AC4596B@www2.open-std.org> References: <20090518082831.8FCC8C178E2@www2.open-std.org> <20090611145654.64B8AC4596B@www2.open-std.org> <20090611180733.9804BC4596B@www2.open-std.org> <20090611182420.3A14AC4596B@www2.open-std.org> X-Mailer: Prayer v1.3.1 Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Sender: owner-sc22wg5@open-std.org Precedence: bulk On Jun 11 2009, Aleksandar Donev wrote: > >> 2) With a defined null value (i.e. like NULL()) > >But that is not a C address, is it? It is a value, for sure. God alone knows. Despite 1.3.19 in Fortran, there is no well-defined meaning of 'address' in C. >> (3) and (4) are merely a different way of pointing >> to valid objects. We experts know that Fortran has no equivalent >> feature, so interoperability is implausible. > >C_F_POINTER is not about *direct* interoperability. It is about >converting a C pointer to a Fortran pointer, so it is perfectly >reasonable to allow one to obtain a Fortran pointer to some C object, >such as the incomplete array at the end of some structure. Yeah. So you end up getting a valid Fortran pointer to something that uisn't a valid Fortran target :-( >> But WHERE in the standard is that made clear? > >No where, but it seems to me if one goes in such details C_F_POINTER has >much bigger problems, notably, there are no stated restrictions on >SHAPE. For example, if you have a C array of size 10, and a pointer to >the middle of it (say element index 5), what is allowed for SHAPE? This >would seem more basic than asking what is allowed if the C pointer is >the address of the end of an structure with an incomplete array at the >end or if it points to the element one past the end of an array. Oh, THAT's not a problem. Both languages have compatible concepts of sequence association (though C's is not called that, of course). Regards, Nick Maclaren, University of Cambridge Computing Service, New Museums Site, Pembroke Street, Cambridge CB2 3QH, England. Email: nmm1@cam.ac.uk Tel.: +44 1223 334761 Fax: +44 1223 334679