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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40848 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m3IGe-0006Ep-8u for qemu-devel@archiver.kernel.org; Tue, 13 Jul 2021 09:16:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48828) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m3IFM-0005P5-24 for qemu-devel@nongnu.org; Tue, 13 Jul 2021 09:14:48 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56162) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m3IFJ-00088w-UP for qemu-devel@nongnu.org; Tue, 13 Jul 2021 09:14:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626182084; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6zHOrn5bHKwrAyKsSczXc+ISl08HqeCPdLfeGYAaZvM=; b=KrEcLtOVGpgGPhltoT2gxZgWbT0dSKxlaYbRyxLi3SpQgZKeAwkivWKQhX3e3Xe6S2bWdl nZEIZVbnjDKqW9q68TQIp+ru+IGBZ34Go4NJg6PDaI0GQlXjyU5xSAixtKpmZ7aXEBt3Mf Q6WNYQKy/KsAVYePFsuCpMnPNFZ3NVw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-163-CrHL7emAO4CJQxZ5HFzvAA-1; Tue, 13 Jul 2021 09:14:41 -0400 X-MC-Unique: CrHL7emAO4CJQxZ5HFzvAA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 982AD18414A1; Tue, 13 Jul 2021 13:14:40 +0000 (UTC) Received: from redhat.com (ovpn-113-49.phx2.redhat.com [10.3.113.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 314A95D6AB; Tue, 13 Jul 2021 13:14:40 +0000 (UTC) Date: Tue, 13 Jul 2021 08:14:38 -0500 From: Eric Blake To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 01/11] nbd/server: Remove unused variable Message-ID: <20210713131438.hx2gp6v2jc2qvba3@redhat.com> References: <20210712215535.1471256-1-richard.henderson@linaro.org> <20210712215535.1471256-2-richard.henderson@linaro.org> <20210713130134.zfti7sgxcw4i3dbd@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210713130134.zfti7sgxcw4i3dbd@redhat.com> User-Agent: NeoMutt/20210205-569-37ed14 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Richard Henderson , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jul 13, 2021 at 08:01:34AM -0500, Eric Blake wrote: > > > @@ -973,7 +973,6 @@ static int nbd_negotiate_meta_queries(NBDClient *client, > > > { > > > int ret; > > > g_autofree char *export_name = NULL; > > > - g_autofree bool *bitmaps = NULL; > > > NBDExportMetaContexts local_meta = {0}; > > Actually, "bitmaps" _is_ used, in cleanup handler, setup by g_autofree. So it's a false positive. > > > > Correct; this patch is wrong, and would cause a memory leak. This is a > false positive in clang, and a known issue that clang is in general > unable to see that g_autofree variables are used, sometimes for their > intentional side effects such as easier memory cleanup as done here. > > I suspect that the definition of g_autofree already uses > __attribute__((unused)) to work around clang's oddities, which means > I'm not sure how to silence clang on this one. Hmm; in glib 2.68.2 (on Fedora 34), g_autofree does NOT include an attribute unused. Thus, does this silence the compiler? (Even cooler would be making the comment a link to an actual bug in the clang database, but I couldn't quickly find one) diff --git i/nbd/server.c w/nbd/server.c index b60ebc3ab6ac..393cbd81c57a 100644 --- i/nbd/server.c +++ w/nbd/server.c @@ -973,7 +973,8 @@ static int nbd_negotiate_meta_queries(NBDClient *client, { int ret; g_autofree char *export_name = NULL; - g_autofree bool *bitmaps = NULL; + /* G_GNUC_UNUSED needed to work around a clang bug */ + g_autofree G_GNUC_UNUSED bool *bitmaps = NULL; NBDExportMetaContexts local_meta = {0}; uint32_t nb_queries; size_t i; -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org