From nobody Sat Feb 7 11:40:21 2026 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 46A20C001DB for ; Fri, 4 Aug 2023 10:58:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230423AbjHDK6p convert rfc822-to-8bit (ORCPT ); Fri, 4 Aug 2023 06:58:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231654AbjHDK5f (ORCPT ); Fri, 4 Aug 2023 06:57:35 -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 712AA524D for ; Fri, 4 Aug 2023 03:56:45 -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-mtapsc-5-bkO1WbUpNhKPKRaGR9bvIg-1; Fri, 04 Aug 2023 11:56:23 +0100 X-MC-Unique: bkO1WbUpNhKPKRaGR9bvIg-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Fri, 4 Aug 2023 11:56:21 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Fri, 4 Aug 2023 11:56:21 +0100 From: David Laight To: "'linux-kernel@vger.kernel.org'" , "'Andy Shevchenko'" , 'Andrew Morton' , "'Matthew Wilcox (Oracle)'" , 'Christoph Hellwig' , "'Jason A. Donenfeld'" , 'Linus Torvalds' Subject: [PATCH v3 5/5] minmax: Relax check to allow comparison between int and small unsigned constants. Thread-Topic: [PATCH v3 5/5] minmax: Relax check to allow comparison between int and small unsigned constants. Thread-Index: AdnGwkt6hGqNS4p3Ts2CQBK2yLMoFA== Date: Fri, 4 Aug 2023 10:56:21 +0000 Message-ID: References: <01e3e09005e9434b8f558a893a47c053@AcuMS.aculab.com> In-Reply-To: <01e3e09005e9434b8f558a893a47c053@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-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Convert constants between 0 and INT_MAX to 'int' prior to comparisons so that min(signed_var, 20u) and, more commonly, min(signed_var, sizeof()) are both valid. Signed-off-by: David Laight --- v3: Fix compiler warnings for 'x >=3D 0' with unsigned/pointer types. v2: Add cast to fix min/max with pointer types. include/linux/minmax.h | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) diff --git a/include/linux/minmax.h b/include/linux/minmax.h index f56611ab486a..8d292aa55f5f 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -8,11 +8,13 @@ /* * min()/max()/clamp() macros must accomplish three things: * - * - avoid multiple evaluations of the arguments (so side-effects like + * - Avoid multiple evaluations of the arguments (so side-effects like * "x++" happen only once) when non-constant. - * - perform signed v unsigned type-checking (to generate compile + * - Perform signed v unsigned type-checking (to generate compile * errors instead of nasty runtime surprises). - * - retain result as a constant expressions when called with only + * Constants from 0 to INT_MAX are cast to (int) so can be used + * in comparisons with signed types. + * - Retain result as a constant expressions when called with only * constant expressions (to avoid tripping VLA warnings in stack * allocation usage). */ @@ -24,9 +26,17 @@ __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \ is_signed_type(typeof(x)), 0) =20 -#define __types_ok(x, y) \ - (__is_signed(x) =3D=3D __is_signed(y) || \ - __is_signed((x) + 0) =3D=3D __is_signed((y) + 0)) +#define __is_noneg_int(x) \ + (__builtin_choose_expr(!__is_constexpr(x), false, \ + __builtin_choose_expr(__is_signed(x), x, 0) >=3D 0 && \ + (x) <=3D (typeof((x) + 0))(long)__INT_MAX__)) + +#define __int_const(x) __builtin_choose_expr(__is_noneg_int(x), (int)(long= )(x), (x)) + +#define __types_ok(x, y) \ + (__is_signed(x) =3D=3D __is_signed(y) || \ + __is_signed((x) + 0) =3D=3D __is_signed((y) + 0) || \ + __is_noneg_int(x) || __is_noneg_int(y)) =20 #define __cmp_op_min < #define __cmp_op_max > @@ -34,24 +44,24 @@ #define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y)) =20 #define __cmp_once(op, x, y, unique_x, unique_y) ({ \ - typeof(x) unique_x =3D (x); \ - typeof(y) unique_y =3D (y); \ + typeof(__int_const(x)) unique_x =3D (x); \ + typeof(__int_const(y)) unique_y =3D (y); \ static_assert(__types_ok(x, y), \ #op "(" #x ", " #y ") signedness error, fix types or consider " #op "_un= signed() before " #op "_t()"); \ __cmp(op, unique_x, unique_y); }) =20 #define __careful_cmp(op, x, y) \ __builtin_choose_expr(__is_constexpr((x) - (y)), \ - __cmp(op, x, y), \ + __cmp(op, __int_const(x), __int_const(y)), \ __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y))) =20 #define __clamp(val, lo, hi) \ ((val) >=3D (hi) ? (hi) : ((val) <=3D (lo) ? (lo) : (val))) =20 #define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \ - typeof(val) unique_val =3D (val); \ - typeof(lo) unique_lo =3D (lo); \ - typeof(hi) unique_hi =3D (hi); \ + typeof(__int_const(val)) unique_val =3D (val); \ + typeof(__int_const(lo)) unique_lo =3D (lo); \ + typeof(__int_const(hi)) unique_hi =3D (hi); \ static_assert(__builtin_choose_expr(__is_constexpr((lo) > (hi)), \ (lo) <=3D (hi), true), \ "clamp() low limit " #lo " greater than high limit " #hi); \ --=20 2.17.1 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)