From owner-sc22wg5+sc22wg5-dom9=www.open-std.org@open-std.org Wed Dec 11 17:38:23 2024 Return-Path: X-Original-To: sc22wg5-dom9 Delivered-To: sc22wg5-dom9@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id EE835357070; Wed, 11 Dec 2024 17:38:22 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from mail-qk1-f181.google.com (mail-qk1-f181.google.com [209.85.222.181]) by www.open-std.org (Postfix) with ESMTP id 85649356D5C for ; Wed, 11 Dec 2024 17:38:22 +0100 (CET) Received: by mail-qk1-f181.google.com with SMTP id af79cd13be357-7b6ef047e9bso44909085a.1 for ; Wed, 11 Dec 2024 08:38:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=stevelionel.com; s=google; t=1733935101; x=1734539901; darn=open-std.org; h=in-reply-to:from:content-language:references:to:subject:user-agent :mime-version:date:message-id:from:to:cc:subject:date:message-id :reply-to; bh=XGuHJHFIwTKd0PdcoU26Caw0BgezE2N3ZONGLl6EjQw=; b=e+ubs8qq5QskAj5Rps6n2fyCidelhmySA9jKG2NJBx0XMw8PITyNMHNRpbkvQ0CgBi LQ3oOgYl/oAt5z/ns6pTWwdKOrakNMnSFCtJ/10G4AXabiDffROc9J8SiPcRl7lYDwzb 59dRrvTTVFSKlZBNssF4R/Mj6P7JLvy1vzzwg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733935101; x=1734539901; h=in-reply-to:from:content-language:references:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=XGuHJHFIwTKd0PdcoU26Caw0BgezE2N3ZONGLl6EjQw=; b=XBMIGhJQvZvMteqtGqvc6+GJSpn91TL3Y5hBLhoYPOTTVSWLwuwt9P5Oy10wOLrfs8 DSXXjFYHLA4yj6OTgSFCJId46sO+4xeqGwkIwkp5OikYZG4HdEbxgFq6GZ432jZv4EHa f8FIkuWA5E3pnu16m8SDbf19DnLtIpcw7Ch43MZyPpy0xi4vTPeI3bXjPkIVJEKVYuZJ ghfQvW1FdRccuZUKMBrR2oWDyqXpKfn24RlQMgwnx058/7dl6nMM0S69ZFrlj8RV7XQL l7a3S4rhUC+jpa3i+5MQFg+UdQZ5ZAWDlxY2VYHk05FQeueuEauJz5ZebRDcgN0V12YO xAqw== X-Gm-Message-State: AOJu0YzfICfIgrnn+1kbZrxnRtA0Dno6EOjc0D8VUnTHIG6mVnutDYy0 7k8TMGIQmIESl4ieWK/yAvgD78sWNj3TO+uNBmN4QMNQUO2vZrlFjD6yCUdzVCWawg6xT28MnBG w X-Gm-Gg: ASbGnctoOaZccm8UxRBaGfAu5FJzMkLGdbyjfdUwICc9kAVTNYfPgg6tiFlvElq6uFL 8bEYCm9OiSiHCx9WfgYV/p4lQAbudCKwQD1VU82+Lwq11ZZN/YXA17srFnos6JW+fI3k+Mg7qqO /vimiwPe9VobH6GwIRElFpKjyEMYCUyBb4Y3MA27KD4e6fIW9SDeUVj0ROA3O6jQqaZVDgVPfjC lnTE/LUhavbal7wp4H2nIc/PjTXoIV4ZoAw/Bup0eJLC8dLoDp/KurhgOOMHpOJxRvZX/j0LNU= X-Google-Smtp-Source: AGHT+IGpTsTgDieDeNUtzDHEIbI/5a0RNFCcVDAIfKmEDgAgaOV3Hb+noecymPznv2om3sDhyp02sw== X-Received: by 2002:a05:620a:4241:b0:7b6:cf60:396d with SMTP id af79cd13be357-7b6ebc25ce0mr564892685a.1.1733935100993; Wed, 11 Dec 2024 08:38:20 -0800 (PST) Received: from [192.168.1.203] ([216.212.3.233]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7b6e23e2b91sm154522685a.9.2024.12.11.08.38.20 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Dec 2024 08:38:20 -0800 (PST) Content-Type: multipart/alternative; boundary="------------Zs8MZTEGV0zoBCEQ6K5tw8rF" Message-ID: Date: Wed, 11 Dec 2024 11:38:19 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [J3] [SC22WG5.6658] Question on the implementation of LOGICAL To: WG5 List References: <20241211115033.05913357070@www.open-std.org> Content-Language: en-US From: Steve Lionel X-Clacks-Overhead: GNU Terry Pratchett In-Reply-To: Sender: owner-sc22wg5@open-std.org Precedence: bulk This is a multi-part message in MIME format. --------------Zs8MZTEGV0zoBCEQ6K5tw8rF Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Of course, I wrote that post in 2000, before C interop was a thing. F2003 says that the C _Bool type is interoperable with LOGICAL(C_BOOL). I think this was a mistake, but we're stuck with it, and this is why Intel made -standard-semantics include -fpscomp logicals. (-fpscomp selects options for compatibility with Microsoft Fortran Powerstation, in case you didn't know.) I once tried to get Intel to add some sort of conditionalization to ISO_C_BINDING such that C_BOOL was -1 unless -fpscomp logicals was in effect, but was unsuccessful. While the main point of my post holds, that being you should not use integer operations nor tests for equality on LOGICAL values, if you interoperate with C, or something that works like C, you will need to make sure that your Fortran code treats LOGICAL values the same way. For MPI, I assume that its kind value for bools would be derived from C_BOOL in ISO_C_BINDING. Steve On 12/11/2024 11:01 AM, Jeff Hammond wrote: > > Thanks, Steve.  That helps.  I misremembered the VAX behavior. > > I used C to set logicals to integers - probably not conforming, but it > works.  The behavior is amusing, but of course, consistent with your > blog and the notion that incorrect programs may produce nonsensical > results. > --------------Zs8MZTEGV0zoBCEQ6K5tw8rF Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit
Of course, I wrote that post in 2000, before C interop was a thing. F2003 says that the C _Bool type is interoperable with LOGICAL(C_BOOL). I think this was a mistake, but we're stuck with it, and this is why Intel made -standard-semantics include -fpscomp logicals. (-fpscomp selects options for compatibility with Microsoft Fortran Powerstation, in case you didn't know.) I once tried to get Intel to add some sort of conditionalization to ISO_C_BINDING such that C_BOOL was -1 unless -fpscomp logicals was in effect, but was unsuccessful.

While the main point of my post holds, that being you should not use integer operations nor tests for equality on LOGICAL values, if you interoperate with C, or something that works like C, you will need to make sure that your Fortran code treats LOGICAL values the same way. For MPI, I assume that its kind value for bools would be derived from C_BOOL in ISO_C_BINDING.

Steve

On 12/11/2024 11:01 AM, Jeff Hammond wrote:

Thanks, Steve.  That helps.  I misremembered the VAX behavior.

 

I used C to set logicals to integers - probably not conforming, but it works.  The behavior is amusing, but of course, consistent with your blog and the notion that incorrect programs may produce nonsensical results.


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