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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 D9A43C4743F for ; Tue, 8 Jun 2021 11:12:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBBDE6128D for ; Tue, 8 Jun 2021 11:12:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231588AbhFHLOK convert rfc822-to-8bit (ORCPT ); Tue, 8 Jun 2021 07:14:10 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:47094 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231172AbhFHLOK (ORCPT ); Tue, 8 Jun 2021 07:14:10 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-30-guQiPO4kPrqaSB27Et2hIQ-1; Tue, 08 Jun 2021 12:12:14 +0100 X-MC-Unique: guQiPO4kPrqaSB27Et2hIQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Tue, 8 Jun 2021 12:12:14 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Tue, 8 Jun 2021 12:12:13 +0100 From: David Laight To: 'Peter Zijlstra' , Ricardo Ribalda CC: "linux-kernel@vger.kernel.org" , "linux-perf-users@vger.kernel.org" , "Ingo Molnar" , Arnaldo Carvalho de Melo Subject: RE: [PATCH] tools/perf: Do not set a variable unless it will be used Thread-Topic: [PATCH] tools/perf: Do not set a variable unless it will be used Thread-Index: AQHXWSUW63LkalkO1EC8vlerZJxmp6sJ+mDw Date: Tue, 8 Jun 2021 11:12:13 +0000 Message-ID: <369424fbd25444d39352d3ee0f24a89d@AcuMS.aculab.com> References: <20210604092638.985694-1-ribalda@chromium.org> In-Reply-To: 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org From: Peter Zijlstra > Sent: 04 June 2021 10:36 > > On Fri, Jun 04, 2021 at 11:26:38AM +0200, Ricardo Ribalda wrote: > > clang-13 triggers the following warning: > > > > bench/inject-buildid.c:351:6: error: variable 'len' set but not used [-Werror,-Wunused-but-set- > variable] > > u64 len = 0; > > > > This patch sets the value to len only if it will be used afterwards. > > My vote would be to kill that warning, what absolute shite. The compiler folk need their heads examining. On one hand they are adding code to initialise everything to avoid leaking information, and on the other they moan when you do defensive coding. There might be a justification for: foo = complex_expression; where, maybe, you might have assigned it to the wrong variable. But for simple constants (especially on declarations) it is really silly. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)