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 2E849C83F11 for ; Sun, 27 Aug 2023 21:52:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229874AbjH0Vvu convert rfc822-to-8bit (ORCPT ); Sun, 27 Aug 2023 17:51:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230186AbjH0Vvj (ORCPT ); Sun, 27 Aug 2023 17:51:39 -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 4E97711A for ; Sun, 27 Aug 2023 14:51:36 -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-21-i_qKFWZgNka4tYyQRpP4Gw-1; Sun, 27 Aug 2023 22:51:33 +0100 X-MC-Unique: i_qKFWZgNka4tYyQRpP4Gw-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; Sun, 27 Aug 2023 22:51:35 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Sun, 27 Aug 2023 22:51:35 +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/+quMQ Date: Sun, 27 Aug 2023 21:51:35 +0000 Message-ID: <4bbdea1710464fa2943663a25bf370c9@AcuMS.aculab.com> References: <20230827083225.7534-1-falcon@tinylab.org> In-Reply-To: <20230827083225.7534-1-falcon@tinylab.org> 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 ... > 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. Since "abc"[2] (etc) is converted to a constant (by gcc and clang except at -O0) and you only need to process "n" "nn" "nnn" "(n + m)" (with variable length n and m) then append some spaces and convert the characters back to digits. 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. I'm not sure how constant the array index need to be. They may well have to be 'integer constant expressions' so cant depend on a previous str[const] value. I just found a(nother) clang bug: int f(void) { return "a"[2]; } compiles to just a 'return'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)