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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 BDB64C43441 for ; Fri, 16 Nov 2018 08:16:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 90569208A3 for ; Fri, 16 Nov 2018 08:16:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 90569208A3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727632AbeKPS2C (ORCPT ); Fri, 16 Nov 2018 13:28:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:49048 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727405AbeKPS2C (ORCPT ); Fri, 16 Nov 2018 13:28:02 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 375C8ACD3 for ; Fri, 16 Nov 2018 08:16:43 +0000 (UTC) Subject: Re: [PATCH 7/9] btrfs-progs: Fix Wmaybe-uninitialized warning To: Nikolay Borisov , linux-btrfs@vger.kernel.org References: <20181116075426.4142-1-wqu@suse.com> <20181116075426.4142-8-wqu@suse.com> <05314eb4-29e5-8c30-05ca-5566ec12eb83@suse.com> From: Qu Wenruo Openpgp: preference=signencrypt Autocrypt: addr=wqu@suse.de; prefer-encrypt=mutual; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWCnQUJCWYC bgAKCRDCPZHzoSX+qAR8B/94VAsSNygx1C6dhb1u1Wp1Jr/lfO7QIOK/nf1PF0VpYjTQ2au8 ihf/RApTna31sVjBx3jzlmpy+lDoPdXwbI3Czx1PwDbdhAAjdRbvBmwM6cUWyqD+zjVm4RTG rFTPi3E7828YJ71Vpda2qghOYdnC45xCcjmHh8FwReLzsV2A6FtXsvd87bq6Iw2axOHVUax2 FGSbardMsHrya1dC2jF2R6n0uxaIc1bWGweYsq0LXvLcvjWH+zDgzYCUB0cfb+6Ib/ipSCYp 3i8BevMsTs62MOBmKz7til6Zdz0kkqDdSNOq8LgWGLOwUTqBh71+lqN2XBpTDu1eLZaNbxSI ilaVzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWBrwIbDAUJA8JnAAAK CRDCPZHzoSX+qA3xB/4zS8zYh3Cbm3FllKz7+RKBw/ETBibFSKedQkbJzRlZhBc+XRwF61mi f0SXSdqKMbM1a98fEg8H5kV6GTo62BzvynVrf/FyT+zWbIVEuuZttMk2gWLIvbmWNyrQnzPl mnjK4AEvZGIt1pk+3+N/CMEfAZH5Aqnp0PaoytRZ/1vtMXNgMxlfNnb96giC3KMR6U0E+siA 4V7biIoyNoaN33t8m5FwEwd2FQDG9dAXWhG13zcm9gnk63BN3wyCQR+X5+jsfBaS4dvNzvQv h8Uq/YGjCoV1ofKYh3WKMY8avjq25nlrhzD/Nto9jHp8niwr21K//pXVA81R2qaXqGbql+zo Message-ID: Date: Fri, 16 Nov 2018 16:16:39 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <05314eb4-29e5-8c30-05ca-5566ec12eb83@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2018/11/16 下午4:13, Nikolay Borisov wrote: > > > On 16.11.18 г. 9:54 ч., Qu Wenruo wrote: >> The only location is the following code: >> >> int level = path->lowest_level + 1; >> BUG_ON(path->lowest_level + 1 >= BTRFS_MAX_LEVEL); >> while(level < BTRFS_MAX_LEVEL) { >> slot = path->slots[level] + 1; >> ... >> } >> path->slots[level] = slot; >> >> Again, it's the stupid compiler needs some hint for the fact that >> we will always enter the while loop for at least once, thus @slot should >> always be initialized. >> >> Fix it by assign level after the BUG_ON(), so the stupid compiler knows >> we will always go into the while loop. >> >> Signed-off-by: Qu Wenruo > > I don't get this warning on gcc 7.3. Also from your changelog it's not > really clear what the compiler is confused about. My gcc 8.2.1 reports it with "make W=1" I'll just update the commit message with the original report: ctree.c: In function 'btrfs_next_sibling_tree_block': ctree.c:2990:21: warning: 'slot' may be used uninitialized in this function [-Wmaybe-uninitialized] path->slots[level] = slot; ~~~~~~~~~~~~~~~~~~~^~~~~~ Thanks, Qu > > Codewise lgtm: > > Reviewed-by: Nikolay Borisov > >> --- >> ctree.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/ctree.c b/ctree.c >> index 46e2ccedc0bf..9c9cb0dfdbf2 100644 >> --- a/ctree.c >> +++ b/ctree.c >> @@ -2961,11 +2961,12 @@ int btrfs_next_sibling_tree_block(struct btrfs_fs_info *fs_info, >> struct btrfs_path *path) >> { >> int slot; >> - int level = path->lowest_level + 1; >> + int level; >> struct extent_buffer *c; >> struct extent_buffer *next = NULL; >> >> BUG_ON(path->lowest_level + 1 >= BTRFS_MAX_LEVEL); >> + level = path->lowest_level + 1; >> while(level < BTRFS_MAX_LEVEL) { >> if (!path->nodes[level]) >> return 1; >>