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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 03C29C742B3 for ; Fri, 12 Jul 2019 11:47:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE6A12083B for ; Fri, 12 Jul 2019 11:47:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726525AbfGLLrq (ORCPT ); Fri, 12 Jul 2019 07:47:46 -0400 Received: from mga18.intel.com ([134.134.136.126]:20311 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726250AbfGLLrq (ORCPT ); Fri, 12 Jul 2019 07:47:46 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Jul 2019 04:47:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,482,1557212400"; d="scan'208";a="157116847" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.145]) by orsmga007.jf.intel.com with ESMTP; 12 Jul 2019 04:47:42 -0700 Received: from andy by smile with local (Exim 4.92) (envelope-from ) id 1hlu1c-0006I1-3T; Fri, 12 Jul 2019 14:47:40 +0300 Date: Fri, 12 Jul 2019 14:47:40 +0300 From: Andy Shevchenko To: Arnd Bergmann Cc: "Rafael J. Wysocki" , Len Brown , Mika Westerberg , Hans de Goede , Sakari Ailus , Rasmus Villemoes , Keith Busch , Heikki Krogerus , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: Re: [PATCH] acpi: fix false-positive -Wuninitialized warning Message-ID: <20190712114740.GX9224@smile.fi.intel.com> References: <20190712090148.36582-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712090148.36582-1-arnd@arndb.de> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Fri, Jul 12, 2019 at 11:01:21AM +0200, Arnd Bergmann wrote: > clang gets confused by an uninitialized variable in what looks > to it like a never executed code path: > > arch/x86/kernel/acpi/boot.c:618:13: error: variable 'polarity' is uninitialized when used here [-Werror,-Wuninitialized] > polarity = polarity ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH; > ^~~~~~~~ > arch/x86/kernel/acpi/boot.c:606:32: note: initialize the variable 'polarity' to silence this warning > int rc, irq, trigger, polarity; > ^ > = 0 > arch/x86/kernel/acpi/boot.c:617:12: error: variable 'trigger' is uninitialized when used here [-Werror,-Wuninitialized] > trigger = trigger ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE; > ^~~~~~~ > arch/x86/kernel/acpi/boot.c:606:22: note: initialize the variable 'trigger' to silence this warning > int rc, irq, trigger, polarity; > ^ > = 0 > > This is unfortunately a design decision in clang and won't be fixed. > > Changing the acpi_get_override_irq() macro to an inline function > reliably avoids the issue. In this particular case it looks fine (perhaps in the future -1 shall be replaced with proper error code). Reviewed-by: Andy Shevchenko But in general it looks like clang obscures use of pretty well working macros. > > Signed-off-by: Arnd Bergmann > --- > include/linux/acpi.h | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/include/linux/acpi.h b/include/linux/acpi.h > index a95cce5e82e7..9426b9aaed86 100644 > --- a/include/linux/acpi.h > +++ b/include/linux/acpi.h > @@ -324,7 +324,10 @@ struct irq_domain *acpi_irq_create_hierarchy(unsigned int flags, > #ifdef CONFIG_X86_IO_APIC > extern int acpi_get_override_irq(u32 gsi, int *trigger, int *polarity); > #else > -#define acpi_get_override_irq(gsi, trigger, polarity) (-1) > +static inline int acpi_get_override_irq(u32 gsi, int *trigger, int *polarity) > +{ > + return -1; > +} > #endif > /* > * This function undoes the effect of one call to acpi_register_gsi(). > -- > 2.20.0 > -- With Best Regards, Andy Shevchenko