From owner-svn-src-all@freebsd.org Thu May 24 04:42:55 2018 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1FA8EEFC82B; Thu, 24 May 2018 04:42:55 +0000 (UTC) (envelope-from glebius@FreeBSD.org) Received: from cell.glebi.us (glebi.us [96.95.210.25]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "cell.glebi.us", Issuer "cell.glebi.us" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id A76A872F8E; Thu, 24 May 2018 04:42:54 +0000 (UTC) (envelope-from glebius@FreeBSD.org) Received: from cell.glebi.us (localhost [127.0.0.1]) by cell.glebi.us (8.15.2/8.15.2) with ESMTPS id w4O4gqmd086965 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 23 May 2018 21:42:52 -0700 (PDT) (envelope-from glebius@FreeBSD.org) Received: (from glebius@localhost) by cell.glebi.us (8.15.2/8.15.2/Submit) id w4O4gqh1086964; Wed, 23 May 2018 21:42:52 -0700 (PDT) (envelope-from glebius@FreeBSD.org) X-Authentication-Warning: cell.glebi.us: glebius set sender to glebius@FreeBSD.org using -f Date: Wed, 23 May 2018 21:42:52 -0700 From: Gleb Smirnoff To: Matthew Macy Cc: src-committers , svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r333860 - head/sys/kern Message-ID: <20180524044252.GW71675@FreeBSD.org> References: <201805190510.w4J5AqfS054367@repo.freebsd.org> <20180523222743.GU71675@FreeBSD.org> <20180523225729.GV71675@FreeBSD.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.5 (2018-04-13) X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 May 2018 04:42:55 -0000 Let me repeat again. The warning is a false positive, and thus assignment isn't useful. I'm not worried about a single instruction, more about polluting the code. If the warning was escalated to build error, and we did carry about building with gcc8, in this case the assignment should be added with a comment /* pacify gcc */. On Wed, May 23, 2018 at 03:59:33PM -0700, Matthew Macy wrote: M> On Wed, May 23, 2018 at 3:57 PM, Gleb Smirnoff wrote: M> > The initialization isn't useful. M> M> It silences a gcc warning. So yes it is. It's this exchange which is not useful. M> M> -M M> M> M> > On Wed, May 23, 2018 at 03:52:42PM -0700, Matthew Macy wrote: M> > M> Talk to the gcc devs. The warning is useful even if there are false positives. M> > M> M> > M> On Wed, May 23, 2018 at 3:27 PM, Gleb Smirnoff wrote: M> > M> > Hi, M> > M> > M> > M> > On Sat, May 19, 2018 at 05:10:52AM +0000, Matt Macy wrote: M> > M> > M> Author: mmacy M> > M> > M> Date: Sat May 19 05:10:51 2018 M> > M> > M> New Revision: 333860 M> > M> > M> URL: https://svnweb.freebsd.org/changeset/base/333860 M> > M> > M> M> > M> > M> Log: M> > M> > M> sendfile: annotate unused value and ensure that npages is actually initialized M> > M> > M> M> > M> > M> Modified: M> > M> > M> head/sys/kern/kern_sendfile.c M> > M> > M> M> > M> > M> Modified: head/sys/kern/kern_sendfile.c M> > M> > M> ============================================================================== M> > M> > M> --- head/sys/kern/kern_sendfile.c Sat May 19 05:09:10 2018 (r333859) M> > M> > M> +++ head/sys/kern/kern_sendfile.c Sat May 19 05:10:51 2018 (r333860) M> > M> > M> @@ -341,7 +341,7 @@ sendfile_swapin(vm_object_t obj, struct sf_io *sfio, o M> > M> > M> } M> > M> > M> M> > M> > M> for (int i = 0; i < npages;) { M> > M> > M> - int j, a, count, rv; M> > M> > M> + int j, a, count, rv __unused; M> > M> > M> M> > M> > M> /* Skip valid pages. */ M> > M> > M> if (vm_page_is_valid(pa[i], vmoff(i, off) & PAGE_MASK, M> > M> > M> @@ -688,6 +688,7 @@ retry_space: M> > M> > M> if (space == 0) { M> > M> > M> sfio = NULL; M> > M> > M> nios = 0; M> > M> > M> + npages = 0; M> > M> > M> goto prepend_header; M> > M> > M> } M> > M> > M> hdr_uio = NULL; M> > M> > M> > M> > This initialization is redundant and a compiler warning if exists is wrong. M> > M> > M> > M> > If we jump down to prepend_header with nios == 0, we won't ever use npages. M> > M> > M> > M> > -- M> > M> > Gleb Smirnoff M> > M> > -- M> > Gleb Smirnoff -- Gleb Smirnoff