From patchwork Sun Feb 25 16:56:58 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Laight X-Patchwork-Id: 206099 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:a81b:b0:108:e6aa:91d0 with SMTP id bq27csp1659145dyb; Sun, 25 Feb 2024 08:58:07 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCWzsGBMIl2qZwdJ0hv8sVQv4WPmTFwGFKhZ1tWy/ClWcx0cw9T/4ms1Ify6x9XPtfwr4N5INUYVQpnK099DKtsKnujt6A== X-Google-Smtp-Source: AGHT+IEqXz/gJQoYurO5wTHDyK0PG7kfJy9mP+QVp1hmDp47jB6aZ244v2sonwOkICiXMr2v5L+d X-Received: by 2002:a05:620a:40ca:b0:783:e30b:3759 with SMTP id g10-20020a05620a40ca00b00783e30b3759mr6992867qko.35.1708880286936; Sun, 25 Feb 2024 08:58:06 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1708880286; cv=pass; d=google.com; s=arc-20160816; b=zgCbggsTIZ9tN+9AmG6xWudoK4LEtVaVlMEGVlWlsDkRVKmXJ3HRWXp2c60JnR/o9B gXXdURNJOoiHogGaB5uBE2AUD7k+M+AdjwrR/CYXLc8mpkLoEWD7k2crszkS5sssf4DL T0oIjoszqCONm59mwbuWyI77+FtJJ5C9RqbvIzRD7INVYus6lJugyn7nfo+906fuH5y0 y6JPMuSqfE5XN4wknKd/nBtz0Bd0LnWAMmbe1E9RKtfTikBpTNlwofbHG9KT+gkdIUnB jN0ENAJxVRES62sPuXKGI/vXm4kvpFTY8UpO8DePcEy4o1cjdz8LwQovFzB9jkV3A1j+ mmdQ== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:accept-language :in-reply-to:references:message-id:date:thread-index:thread-topic :subject:cc:to:from; bh=rsRmR/5ns1TyNV7cG+3v8oWYZhfwk+FvC/YgG4vlK0I=; fh=nGE692sbVdRvha6RYbzMUXtm1nr/30sV7frdtDN2z14=; b=fe0uEvxDMi3WZh28S2NpHMiGZgfd0bMxOGvkqU6wA+5n6Z0PH4A2N/4VCPrnMOohCk bP5XWafM786GJmqNfCkbKFytmN0C5xVF0ctaq6BRzo6q72oHBaXg+DpFQoJcsEHY5XKI upBzxDG03hi2hHP4X3SI/2KibOxWlZjy503sIzBWvqb8V3M1CvU1xLm6hDyb+b7tbOaL lotGhLUlCAcSIRCk3frIsnIPxUhtreMu/BEOisxdlT8l0FUYIgqQVneH9g4TH0BjJeXk oKKZ4QJXwqhn87j30JuoJmgenqZiu/UeHxTusoJzeCaRA5iFh/m0bxezi4JQ8JuD+7sL 71Mg==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; arc=pass (i=1 spf=pass spfdomain=aculab.com dmarc=pass fromdomain=aculab.com); spf=pass (google.com: domain of linux-kernel+bounces-80220-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) smtp.mailfrom="linux-kernel+bounces-80220-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=aculab.com Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org. [147.75.199.223]) by mx.google.com with ESMTPS id t11-20020a05620a450b00b00787cc7e1c7dsi1705590qkp.137.2024.02.25.08.58.06 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 25 Feb 2024 08:58:06 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-80220-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223; Authentication-Results: mx.google.com; arc=pass (i=1 spf=pass spfdomain=aculab.com dmarc=pass fromdomain=aculab.com); spf=pass (google.com: domain of linux-kernel+bounces-80220-ouuuleilei=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) smtp.mailfrom="linux-kernel+bounces-80220-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=aculab.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 91A8B1C2040D for ; Sun, 25 Feb 2024 16:58:06 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9D3BA156C2; Sun, 25 Feb 2024 16:57:13 +0000 (UTC) Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0ABE1182D4 for ; Sun, 25 Feb 2024 16:57:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.58.86.151 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708880232; cv=none; b=KjBekuj2Yl4gVKTGZ6o55r+1pUvxKFbafedZJ6dlrDv7YeSE89OBHpLHvbUD9j7O6UQyjCpkwtMfpresrdku99GOjA38AIYIdl6U0KsSV277+tYjkXHnevCtY/2ywwQzrfhxC4TlFOkKIOG/FN2Zo3x+Il4FUeQuWg4WoZVTemc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708880232; c=relaxed/simple; bh=ldiOEy1AqqZRm2jpxplq9I8qQHwbubdPAOsFwLgRl3Q=; h=From:To:CC:Subject:Date:Message-ID:References:In-Reply-To: MIME-Version:Content-Type; b=UZ4KMA78Pkf0Xx4aIBjXSX5UVT3zLrXbA9LLdBBJ+A306e+5+MgilN90aZJW9A0G4l/YIXZ3nu84yHHgoJffJsAULZvNPTjIGenC8IdPKCBvxlS/zXlFXUWHYNyfB0kR5USXpu6Z1E8N7MPIM1Ja6M1hkveTiDiv2WtvviSnV3M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ACULAB.COM; spf=pass smtp.mailfrom=aculab.com; arc=none smtp.client-ip=185.58.86.151 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ACULAB.COM Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=aculab.com 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-209-DBxHGHkZP8yW0XsruhqEOw-1; Sun, 25 Feb 2024 16:57:00 +0000 X-MC-Unique: DBxHGHkZP8yW0XsruhqEOw-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; Sun, 25 Feb 2024 16:56:59 +0000 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Sun, 25 Feb 2024 16:56:59 +0000 From: David Laight To: "'linux-kernel@vger.kernel.org'" , "'Linus Torvalds'" , 'Netdev' , "'dri-devel@lists.freedesktop.org'" CC: 'Jens Axboe' , "'Matthew Wilcox (Oracle)'" , 'Christoph Hellwig' , "'linux-btrfs@vger.kernel.org'" , "'Andrew Morton'" , 'Andy Shevchenko' , "'David S . Miller'" , 'Dan Carpenter' , "'Jani Nikula'" Subject: [PATCH next v2 11/11] minmax: min() and max() don't need to return constant expressions Thread-Topic: [PATCH next v2 11/11] minmax: min() and max() don't need to return constant expressions Thread-Index: AdpoC6KUHy5Z1N7yRkiaBkc7ZdEdRQ== Date: Sun, 25 Feb 2024 16:56:58 +0000 Message-ID: References: <0fff52305e584036a777f440b5f474da@AcuMS.aculab.com> In-Reply-To: <0fff52305e584036a777f440b5f474da@AcuMS.aculab.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791890855688637758 X-GMAIL-MSGID: 1791890855688637758 After changing the handful of places max() was used to size an on-stack array to use max_const() it is no longer necessary for min() and max() to return constant expressions from constant inputs. Remove the associated logic to reduce the expanded text. Remove the 'hack' that allowed max(bool, bool). Fixup the initial block comment to match current reality. Signed-off-by: David Laight --- include/linux/minmax.h | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) Changes for v2: - Typographical and spelling corrections to the commit messages. Patches unchanged. diff --git a/include/linux/minmax.h b/include/linux/minmax.h index c08916588425..5e65c98ff256 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -8,13 +8,10 @@ #include /* - * min()/max()/clamp() macros must accomplish three things: + * min()/max()/clamp() macros must accomplish several things: * * - Avoid multiple evaluations of the arguments (so side-effects like * "x++" happen only once) when non-constant. - * - Retain result as a constant expressions when called with only - * constant expressions (to avoid tripping VLA warnings in stack - * allocation usage). * - Perform signed v unsigned type-checking (to generate compile * errors instead of nasty runtime surprises). * - Unsigned char/short are always promoted to signed int and can be @@ -22,13 +19,19 @@ * - Unsigned arguments can be compared against non-negative signed constants. * - Comparison of a signed argument against an unsigned constant fails * even if the constant is below __INT_MAX__ and could be cast to int. + * + * The return value of min()/max() is not a constant expression for + * constant parameters - so will trigger a VLA warging if used to size + * an on-stack array. + * Instead use min_const() or max_const() which do generate constant + * expressions and are also valid for static initialisers. */ #define __typecheck(x, y) \ (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) /* Allow unsigned compares against non-negative signed constants. */ #define __is_ok_unsigned(x) \ - (is_unsigned_type(typeof(x)) || (__is_constexpr(x) ? (x) + 0 >= 0 : 0)) + (is_unsigned_type(typeof(x)) || (__is_constexpr(x) ? (x) >= 0 : 0)) /* Check for signed after promoting unsigned char/short to int */ #define __is_ok_signed(x) is_signed_type(typeof((x) + 0)) @@ -53,12 +56,10 @@ typeof(y) __y_##uniq = (y); \ __cmp(op, __x_##uniq, __y_##uniq); }) -#define __careful_cmp(op, x, y, uniq) \ - __builtin_choose_expr(__is_constexpr((x) - (y)), \ - __cmp(op, x, y), \ - ({ _Static_assert(__types_ok(x, y), \ - #op "(" #x ", " #y ") signedness error, fix types or consider u" #op "() before " #op "_t()"); \ - __cmp_once(op, x, y, uniq); })) +#define __careful_cmp(op, x, y, uniq) ({ \ + _Static_assert(__types_ok(x, y), \ + #op "(" #x ", " #y ") signedness error, fix types or consider u" #op "() before " #op "_t()"); \ + __cmp_once(op, x, y, uniq); }) #define __careful_cmp_const(op, x, y) \ (BUILD_BUG_ON_ZERO(!__is_constexpr((x) - (y))) + \