From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66E00C83F17 for ; Mon, 28 Aug 2023 09:47:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229525AbjH1Jqc convert rfc822-to-8bit (ORCPT ); Mon, 28 Aug 2023 05:46:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230293AbjH1JqZ (ORCPT ); Mon, 28 Aug 2023 05:46:25 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 019FC10E for ; Mon, 28 Aug 2023 02:46:14 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with both STARTTLS and AUTH (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-243-xG4-vW29Mi-XX8dfW8eG2w-1; Mon, 28 Aug 2023 10:46:12 +0100 X-MC-Unique: xG4-vW29Mi-XX8dfW8eG2w-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Mon, 28 Aug 2023 10:46:14 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Mon, 28 Aug 2023 10:46:14 +0100 From: David Laight To: 'Zhangjin Wu' , "'w@1wt.eu'" CC: "'arnd@arndb.de'" , "'linux-kernel@vger.kernel.org'" , "'linux-kselftest@vger.kernel.org'" , "'thomas@t-8ch.de'" , "'tanyuan@tinylab.org'" Subject: RE: [RFC] tools/nolibc: replace duplicated -ENOSYS return with single -ENOSYS return Thread-Topic: [RFC] tools/nolibc: replace duplicated -ENOSYS return with single -ENOSYS return Thread-Index: AQHZ2MEQNQnWfqnECUm1iJ9YHQny8K/+quMQgADLxVA= Date: Mon, 28 Aug 2023 09:46:14 +0000 Message-ID: <6819b8e273dc44e18f14be148549b828@AcuMS.aculab.com> References: <20230827083225.7534-1-falcon@tinylab.org> <4bbdea1710464fa2943663a25bf370c9@AcuMS.aculab.com> In-Reply-To: <4bbdea1710464fa2943663a25bf370c9@AcuMS.aculab.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org From: David Laight > Sent: 27 August 2023 22:52 > > ... > > Of course, we can also use the __stringify() trick to do so, but it is > > expensive (bigger size, worse performance) to unstringify and get the number > > again, the expensive atoi() 'works' for the numeric __NR_*, but not work for > > (__NR_*_base + offset) like __NR_* definitions (used by ARM and MIPS), a simple > > interpreter is required for such cases and it is more expensive than atoi(). > > > > /* not for ARM and MIPS */ > > > > static int atoi(const char *s); > > #define __get_nr(name) __nr_atoi(__stringify(__NR_##name)) > > #define __nr_atoi(str) (str[0] == '_' ? -1L : ___nr_atoi(str)) > > #define ___nr_atoi(str) (str[0] == '(' ? -1L : atoi(str)) > > > > Welcome more discussion or let's simply throw away this direction ;-) > > While it will look horrid the it ought to be possible to > get the compiler to evaluate the string. ... > So something that starts: > #define dig(c) (c < '0' || c > '9' ? 999999 : c - '0') > str[0] == '_' ? -1 : > str[0] != '(' ? str[1] == ' ' ? dig(str[0]) : > str[2] == '1' ? (dig(str[0]) * 10 + dig(str[1]) : > Any unexpected character will expand the 99999 and generate > an over-large result. See https://godbolt.org/z/rear4c1hj That will convert "1234" or "(1234 + 5678)" (or shorter numbers) as a compile-time constant. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)