From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 BE351353A87; Thu, 10 Sep 2026 22:35:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789079727; cv=none; b=MSwlB7Gi+xjvGS8J3jZOIJBKTXh/pmG2AuCMs/4oS5q8Ox8OX4/xseqmjLLbZcqSqt9DLUjHcwJTbc1wUV4j/cZy++bIoxEVcHNOxi/NK/kWDHeBAyoQKI+XZv+mvnZAILRPA1weIiBBp4IuAfxjZNuqt1MekDRllfgujP5dWRg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789079727; c=relaxed/simple; bh=0VW+qtvSUgh4xyQN099hXLbA85ebdbDwoAQ1pLlmu/8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=u7qI4zCeLWYLpBUX4T4jhgMIAdfubsQ0QX6h/YRfCg1b3J/QYVIPOLraF2822oc1/Fh37a/eH2A4WYzQw8/kSGcKGGD0FOm7HCeXIGCIIciab6/lT11BVYkOTd71HLnCeBvEOkwOZXLPIVjKXiUmIJJ2yVCaAs7aS1PXV39vLeA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fjfXeFxv; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fjfXeFxv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9654F1F000FF; Thu, 10 Sep 2026 22:35:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789079725; bh=STkBHGrY8NPn9tPJq9ZdQdMGtxmiRBYe6smZsSwC3qI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=fjfXeFxvAmvRp5i10QZQUXJHVhAIlZR2E5BxaUeqTMPZBl0d3wuAExfDvBibSwnDC yr3Bhcxo6q93dW5Yd6zgLhCM36coB5mJgWNID03esCLuLu0gWhkCLFaRmX2mWb5MsA G6L8IrLiVJDrqChJr1OYCIfA5FtTnxxX4N2tXrPiHuKFpOp0a/DQHmpaVS85/JRMa6 PLVDcSZxU7GRQul6JODgziZN0vnr3e3ZRLQxuU7xxq6jLaDeahBA/ffOeeSPeovLqq sqQsHclNV/fDSSfL0jSxDleafLFwKzVIiJfEK80fjdeCEsjmMyo9qyc784Hcn02G8W c2H8RPwQ6cmsg== Date: Thu, 10 Sep 2026 15:35:20 -0700 From: Nathan Chancellor To: kernel test robot Cc: Kuan-Wei Chiu , llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org, Andrew Morton , Linux Memory Management List , Guan-Chun Wu <409411716@gms.tku.edu.tw>, David Laight Subject: Re: lib/base64.c:58:18: warning: implicit conversion from 'int' to 's8' (aka 'signed char') changes value from 131 to -125 Message-ID: <20260910223520.GA3375179@ax162> References: <202609110514.S0a0FD6a-lkp@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202609110514.S0a0FD6a-lkp@intel.com> On Fri, Sep 11, 2026 at 06:07:30AM +0800, kernel test robot wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: 50d05c7c76c96b90462f24debacca971d2e86713 > commit: c4eb7ad32eab13ba64cc452c6f43d518b63f5e03 lib/base64: optimize base64_decode() with reverse lookup tables > date: 10 months ago > config: hexagon-allnoconfig (https://download.01.org/0day-ci/archive/20260911/202609110514.S0a0FD6a-lkp@intel.com/config) > compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project d3db069999553568848400c84cbf815c03f5470f) > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260911/202609110514.S0a0FD6a-lkp@intel.com/reproduce) > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > the same patch/commit), kindly add following tags > | Fixes: c4eb7ad32eab ("lib/base64: optimize base64_decode() with reverse lookup tables") > | Reported-by: kernel test robot > | Closes: https://lore.kernel.org/oe-kbuild-all/202609110514.S0a0FD6a-lkp@intel.com/ > > All warnings (new ones prefixed by >>): > > >> lib/base64.c:58:18: warning: implicit conversion from 'int' to 's8' (aka 'signed char') changes value from 131 to -125 [-Wconstant-conversion] > 58 | [BASE64_IMAP] = BASE64_REV_INIT('+', ',') > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:52:2: note: expanded from macro 'BASE64_REV_INIT' > 48 | #define BASE64_REV_INIT(ch_62, ch_63) { \ > | ~ > 49 | [0 ... 0x1f] = -1, \ > 50 | INIT_32(0x20, ch_62, ch_63), \ > 51 | INIT_32(0x40, ch_62, ch_63), \ > 52 | INIT_32(0x60, ch_62, ch_63), \ > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:46:50: note: expanded from macro 'INIT_32' > 46 | #define INIT_32(v, ...) INIT_16(v, __VA_ARGS__), INIT_16((v) + 16, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:45:49: note: expanded from macro 'INIT_16' > 45 | #define INIT_16(v, ...) INIT_8(v, __VA_ARGS__), INIT_8((v) + 8, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all) > lib/base64.c:43:48: note: expanded from macro 'INIT_4' > 43 | #define INIT_4(v, ...) INIT_2(v, __VA_ARGS__), INIT_2((v) + 2, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:42:48: note: expanded from macro 'INIT_2' > 42 | #define INIT_2(v, ...) INIT_1(v, __VA_ARGS__), INIT_1((v) + 1, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:34:42: note: expanded from macro 'INIT_1' > 34 | : (v) >= '0' && (v) <= '9' ? (v) - '0' + 52 \ > | ~~~~~~~~~~^~~~ > lib/base64.c:58:18: warning: implicit conversion from 'int' to 's8' (aka 'signed char') changes value from 130 to -126 [-Wconstant-conversion] > 58 | [BASE64_IMAP] = BASE64_REV_INIT('+', ',') > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:52:2: note: expanded from macro 'BASE64_REV_INIT' > 48 | #define BASE64_REV_INIT(ch_62, ch_63) { \ > | ~ > 49 | [0 ... 0x1f] = -1, \ > 50 | INIT_32(0x20, ch_62, ch_63), \ > 51 | INIT_32(0x40, ch_62, ch_63), \ > 52 | INIT_32(0x60, ch_62, ch_63), \ > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:46:50: note: expanded from macro 'INIT_32' > 46 | #define INIT_32(v, ...) INIT_16(v, __VA_ARGS__), INIT_16((v) + 16, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:45:49: note: expanded from macro 'INIT_16' > 45 | #define INIT_16(v, ...) INIT_8(v, __VA_ARGS__), INIT_8((v) + 8, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all) > lib/base64.c:43:48: note: expanded from macro 'INIT_4' > 43 | #define INIT_4(v, ...) INIT_2(v, __VA_ARGS__), INIT_2((v) + 2, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:42:24: note: expanded from macro 'INIT_2' > 42 | #define INIT_2(v, ...) INIT_1(v, __VA_ARGS__), INIT_1((v) + 1, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:34:42: note: expanded from macro 'INIT_1' > 34 | : (v) >= '0' && (v) <= '9' ? (v) - '0' + 52 \ > | ~~~~~~~~~~^~~~ > lib/base64.c:58:18: warning: implicit conversion from 'int' to 's8' (aka 'signed char') changes value from 129 to -127 [-Wconstant-conversion] > 58 | [BASE64_IMAP] = BASE64_REV_INIT('+', ',') > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:52:2: note: expanded from macro 'BASE64_REV_INIT' > 48 | #define BASE64_REV_INIT(ch_62, ch_63) { \ > | ~ > 49 | [0 ... 0x1f] = -1, \ > 50 | INIT_32(0x20, ch_62, ch_63), \ > 51 | INIT_32(0x40, ch_62, ch_63), \ > 52 | INIT_32(0x60, ch_62, ch_63), \ > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:46:50: note: expanded from macro 'INIT_32' > 46 | #define INIT_32(v, ...) INIT_16(v, __VA_ARGS__), INIT_16((v) + 16, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:45:49: note: expanded from macro 'INIT_16' > 45 | #define INIT_16(v, ...) INIT_8(v, __VA_ARGS__), INIT_8((v) + 8, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all) > lib/base64.c:43:24: note: expanded from macro 'INIT_4' > 43 | #define INIT_4(v, ...) INIT_2(v, __VA_ARGS__), INIT_2((v) + 2, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:42:48: note: expanded from macro 'INIT_2' > 42 | #define INIT_2(v, ...) INIT_1(v, __VA_ARGS__), INIT_1((v) + 1, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:34:42: note: expanded from macro 'INIT_1' > 34 | : (v) >= '0' && (v) <= '9' ? (v) - '0' + 52 \ > | ~~~~~~~~~~^~~~ > lib/base64.c:58:18: warning: implicit conversion from 'int' to 's8' (aka 'signed char') changes value from 128 to -128 [-Wconstant-conversion] > 58 | [BASE64_IMAP] = BASE64_REV_INIT('+', ',') > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:52:2: note: expanded from macro 'BASE64_REV_INIT' > 48 | #define BASE64_REV_INIT(ch_62, ch_63) { \ > | ~ > 49 | [0 ... 0x1f] = -1, \ > 50 | INIT_32(0x20, ch_62, ch_63), \ > 51 | INIT_32(0x40, ch_62, ch_63), \ > 52 | INIT_32(0x60, ch_62, ch_63), \ > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:46:50: note: expanded from macro 'INIT_32' > 46 | #define INIT_32(v, ...) INIT_16(v, __VA_ARGS__), INIT_16((v) + 16, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/base64.c:45:49: note: expanded from macro 'INIT_16' > 45 | #define INIT_16(v, ...) INIT_8(v, __VA_ARGS__), INIT_8((v) + 8, __VA_ARGS__) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ > note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all) > lib/base64.c:43:24: note: expanded from macro 'INIT_4' > 43 | #define INIT_4(v, ...) INIT_2(v, __VA_ARGS__), INIT_2((v) + 2, __VA_ARGS__) I have not looked into the legitimacy of this warning yet but it comes about from a recent change to fix -Wconstant-conversion in clang: https://github.com/llvm/llvm-project/commit/a5ef934a8d295dc03be3960f2b3744ec2e53238e -- Cheers, Nathan