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 A4576E81E10 for ; Fri, 6 Oct 2023 15:51:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232900AbjJFPvQ convert rfc822-to-8bit (ORCPT ); Fri, 6 Oct 2023 11:51:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232888AbjJFPvO (ORCPT ); Fri, 6 Oct 2023 11:51:14 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1916AB9 for ; Fri, 6 Oct 2023 08:51:11 -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-166-Eb7wJLAQNCuk2F_0YS58DQ-1; Fri, 06 Oct 2023 16:51:07 +0100 X-MC-Unique: Eb7wJLAQNCuk2F_0YS58DQ-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; Fri, 6 Oct 2023 16:51:06 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Fri, 6 Oct 2023 16:51:06 +0100 From: David Laight To: 'Kees Cook' CC: "linux-kernel@vger.kernel.org" , "'linux@rasmusvillemoes.dk'" , 'Steven Rostedt' , "'bvanassche@acm.org'" , "torvalds@linux-foundation.org" , "Nathan Chancellor" , Nick Desaulniers , Arnd Bergmann , "akpm@linux-foundation.org" Subject: RE: [PATCH v2 next] compiler.h: Move __is_constexpr() to compiler.h. Thread-Topic: [PATCH v2 next] compiler.h: Move __is_constexpr() to compiler.h. Thread-Index: AQHZ96gTRq31SBDNvUGrpdwig3TLHLA8553w Date: Fri, 6 Oct 2023 15:51:06 +0000 Message-ID: <321c3c0984e64e9cbd1b034755611710@AcuMS.aculab.com> References: <2a6680bbe2e84459816a113730426782@AcuMS.aculab.com> <202310050921.F0B15702D4@keescook> In-Reply-To: <202310050921.F0B15702D4@keescook> 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-kernel@vger.kernel.org It can also be defined more portably as: #define __is_constexpr(x) \ _Generic(0 ? (void *)((long)(x) * 0) : (int *)0, int *: 1, void *: 0) Which doesn't rely on 'sizeof (void)' being valid. But that is for another day. There is also: #define is_pointer_type(type) __is_constexpr((type)1) David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)