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 X-Spam-Level: X-Spam-Status: No, score=-13.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29E59C4332B for ; Thu, 19 Mar 2020 20:31:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB39A2072D for ; Thu, 19 Mar 2020 20:31:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=akamai.com header.i=@akamai.com header.b="H3mDhUz8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727256AbgCSUbC (ORCPT ); Thu, 19 Mar 2020 16:31:02 -0400 Received: from mx0a-00190b01.pphosted.com ([67.231.149.131]:65002 "EHLO mx0a-00190b01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727023AbgCSUbB (ORCPT ); Thu, 19 Mar 2020 16:31:01 -0400 X-Greylist: delayed 1631 seconds by postgrey-1.27 at vger.kernel.org; Thu, 19 Mar 2020 16:31:00 EDT Received: from pps.filterd (m0050093.ppops.net [127.0.0.1]) by m0050093.ppops.net-00190b01. (8.16.0.42/8.16.0.42) with SMTP id 02JJxfgF004755; Thu, 19 Mar 2020 20:03:45 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=akamai.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=jan2016.eng; bh=mUn3O9VmAsOwEKC1EoFw6DJt4hCpb0XLTybtGwOerzo=; b=H3mDhUz8fe+A9e9ktPUSPTDtcrbu+SEidGulMs4udhqLWYBaJFOd/ezi5WXrygFqyZ8t 2QnYbAM+u5wT1rVqSJcpNPW1JKeduQ9oGfdY5bMpZUAX4MMrFgzYp/7/k8c1KZCKillL HxbY+ao8DdqhU4bSYmlhhSr+FjrelLEjjuF1PjgrslCiIN7mA+tXRkTVaxBn7s9hwtlH zF6kFSn0tsQS8is/VKSMpuZb4cvTQFEwvUzo7A6MBNc1Pr/xdvEV6K0bQ4HcmTZxDxn2 lUgAeXm8hnf6lwHG1WlFUy5q5Ip2HXUJNrB1WBeAUJBQUPoJuWqFD7ePLQcBcPA5WMsj SQ== Received: from prod-mail-ppoint3 (prod-mail-ppoint3.akamai.com [96.6.114.86] (may be forged)) by m0050093.ppops.net-00190b01. with ESMTP id 2yrqduruqg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 19 Mar 2020 20:03:45 +0000 Received: from pps.filterd (prod-mail-ppoint3.akamai.com [127.0.0.1]) by prod-mail-ppoint3.akamai.com (8.16.0.27/8.16.0.27) with SMTP id 02JK3Z4Y001211; Thu, 19 Mar 2020 16:03:44 -0400 Received: from prod-mail-relay14.akamai.com ([172.27.17.39]) by prod-mail-ppoint3.akamai.com with ESMTP id 2yrtm0f8u2-1; Thu, 19 Mar 2020 16:03:42 -0400 Received: from [0.0.0.0] (prod-ssh-gw01.bos01.corp.akamai.com [172.27.119.138]) by prod-mail-relay14.akamai.com (Postfix) with ESMTP id C2BDF85C23; Thu, 19 Mar 2020 20:03:39 +0000 (GMT) Subject: Re: [PATCH v2] dynamic_debug: Use address-of operator on section symbols To: Nathan Chancellor Cc: linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nick Desaulniers , Andrew Morton References: <20200220051320.10739-1-natechancellor@gmail.com> <20200319015909.GA8292@ubuntu-m2-xlarge-x86> From: Jason Baron Message-ID: <4b766edb-73e2-c295-22eb-b501405baa9f@akamai.com> Date: Thu, 19 Mar 2020 16:03:39 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200319015909.GA8292@ubuntu-m2-xlarge-x86> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-19_08:2020-03-19,2020-03-19 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-2002250000 definitions=main-2003190083 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-19_07:2020-03-19,2020-03-19 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 phishscore=0 clxscore=1011 impostorscore=0 priorityscore=1501 lowpriorityscore=0 suspectscore=0 bulkscore=0 adultscore=0 mlxlogscore=999 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003190083 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/18/20 9:59 PM, Nathan Chancellor wrote: > On Wed, Feb 19, 2020 at 10:13:20PM -0700, Nathan Chancellor wrote: >> Clang warns: >> >> ../lib/dynamic_debug.c:1034:24: warning: array comparison always >> evaluates to false [-Wtautological-compare] >> if (__start___verbose == __stop___verbose) { >> ^ >> 1 warning generated. >> >> These are not true arrays, they are linker defined symbols, which are >> just addresses. Using the address of operator silences the warning and >> does not change the resulting assembly with either clang/ld.lld or >> gcc/ld (tested with diff + objdump -Dr). >> >> Link: https://github.com/ClangBuiltLinux/linux/issues/894 >> Suggested-by: Nick Desaulniers >> Signed-off-by: Nathan Chancellor >> --- >> v1 -> v2: https://lore.kernel.org/lkml/20200219045423.54190-5-natechancellor@gmail.com/ >> >> * No longer a series because there is no prerequisite patch. >> * Use address-of operator instead of casting to unsigned long. >> >> lib/dynamic_debug.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c >> index aae17d9522e5..8f199f403ab5 100644 >> --- a/lib/dynamic_debug.c >> +++ b/lib/dynamic_debug.c >> @@ -1031,7 +1031,7 @@ static int __init dynamic_debug_init(void) >> int n = 0, entries = 0, modct = 0; >> int verbose_bytes = 0; >> >> - if (__start___verbose == __stop___verbose) { >> + if (&__start___verbose == &__stop___verbose) { >> pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n"); >> return 1; >> } >> -- >> 2.25.1 >> > > Gentle ping for review/acceptance. > > Cheers, > Nathan Works for me. Acked-by: Jason Baron