From owner-svn-src-head@FreeBSD.ORG Mon May 13 06:53:17 2013 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 1C8C4161 for ; Mon, 13 May 2013 06:53:17 +0000 (UTC) (envelope-from peter@wemm.org) Received: from mail-vb0-x22a.google.com (mail-vb0-x22a.google.com [IPv6:2607:f8b0:400c:c02::22a]) by mx1.freebsd.org (Postfix) with ESMTP id CEC2E9A5 for ; Mon, 13 May 2013 06:53:16 +0000 (UTC) Received: by mail-vb0-f42.google.com with SMTP id w16so4955633vbf.15 for ; Sun, 12 May 2013 23:53:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wemm.org; s=google; h=mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; bh=gBH0JeiCFSBYLMNBVYadiKSnJL3bNbGpizDZMcbYa1A=; b=n7LFosYopL6nSSsBmnPGhWX6PLf1b5AuHoFnnHYb3gTWdJBkqK9tTsgtvNCgR3BoFA 3QM8rSbtc4JssVOE3TPlnjf5l6bRnmQg8yHVbPvNJhqee/KsKib0D7CqhVLxfiJcldhf 6UylnqKSpRykTnFHJy3g0rXLKV6XADS4MewgI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:cc:content-type:x-gm-message-state; bh=gBH0JeiCFSBYLMNBVYadiKSnJL3bNbGpizDZMcbYa1A=; b=A4UNFb+8V5KsPJUTCZ6NfKrf6oJ3oFSOPO+jlNmfmn0iyzbaayop54LjUm15gr09Df WXH3lIq9QV1exn5qytwb2SWOmW1v8+te2cW+zp5pValQ1G+vLAoR3ICuxwhLNqj5rsaZ osHhvdPQr+IcQFLcMh153XtmXMzaJa20mLjSrugZfuzbLyzVCYYKJlftHIUA1oOmxBBd fWP6z/hq50imXiTN8hnPbCHsmvbqS7JEtY2JefeLAFVdkIi/7voFaIXnZbf7M7mnUJad Yn9qaU9BuPSvYh7KPyL6M/BbamzdHYV/YfmB01TLR1CY9QIqlFLyg+cHP3As8TkXC1s/ lzOQ== MIME-Version: 1.0 X-Received: by 10.58.54.101 with SMTP id i5mr17589481vep.43.1368427996201; Sun, 12 May 2013 23:53:16 -0700 (PDT) Received: by 10.220.197.66 with HTTP; Sun, 12 May 2013 23:53:16 -0700 (PDT) In-Reply-To: <51900E57.80608@rice.edu> References: <201305121650.r4CGoJL0087149@svn.freebsd.org> <51900B97.20406@freebsd.org> <51900E57.80608@rice.edu> Date: Sun, 12 May 2013 23:53:16 -0700 Message-ID: Subject: Re: svn commit: r250577 - head/sys/vm From: Peter Wemm To: Alan Cox Content-Type: text/plain; charset=ISO-8859-1 X-Gm-Message-State: ALoCoQk6RQ2Iz0up5xmuYoucKqro7Ifa41+bLlmtfyLQhhUdVCf88opkWOLYAtnkalg+YknjQ2fZ Cc: Alan Cox , svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Andrey Chernov X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 May 2013 06:53:17 -0000 On Sun, May 12, 2013 at 2:49 PM, Alan Cox wrote: > On 05/12/2013 16:37, Andrey Chernov wrote: >> On 12.05.2013 20:50, Alan Cox wrote: >> >> GNU cc errors related to part of diff below: >> cc1: warnings being treated as errors >> ../../../vm/vm_page.c: In function 'vm_page_alloc': >> ../../../vm/vm_page.c:1209: warning: 'mpred' may be used uninitialized >> in this function >> *** [vm_page.o] Error code 1 >> Formally yes, mpred here can be left unitialized. > > No, it can't. The code amounts to > > if ("x") > mpred = ... ; > ... > if ("x") > use mpred; > ... > if ("x") > use mpred; > > where "x" is "object != NULL". Moreover, there are no assignments to > the variable "object" or aliases by which the variable "object" can be > modified over the lifespan of "mpred". So, this is flawed analysis by > our antique gcc. Regardless of who's right or wrong, you've broken about half the freebsd.org cluster. It uses a mixture of gcc and clang to catch sillyness like this. -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV