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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 4FAE2C433E0 for ; Wed, 3 Jun 2020 16:07:42 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 14EEE205CB for ; Wed, 3 Jun 2020 16:07:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XvLMgkED" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 14EEE205CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41056 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jgVvZ-0003vS-Cq for qemu-devel@archiver.kernel.org; Wed, 03 Jun 2020 12:07:41 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45076) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jgVuu-0003Km-Aq for qemu-devel@nongnu.org; Wed, 03 Jun 2020 12:07:00 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:54968 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jgVut-0001eT-0L for qemu-devel@nongnu.org; Wed, 03 Jun 2020 12:06:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591200417; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5g0xWKQHK3OchzfH5fA/OUO7nHT8833CftAc9cSmOI0=; b=XvLMgkEDHKBbQEpmrXsymSXZf7xUajyCpdfBUUETiO+7nSiaNoGM/+hW/s31RVOw6UeMeI 3BNeuY/7jaZMziHZrkuI7YCwoeyNGglK4agprwKjaAPusTzsvR8aMJhgP3KrYnKj+utd7o SsT33D2Bnrq4qIQAbY2NHvnjqZB5w4Y= 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-11-cDavETnrNDaZM4xnKFeQ3g-1; Wed, 03 Jun 2020 12:06:55 -0400 X-MC-Unique: cDavETnrNDaZM4xnKFeQ3g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EF55718A0764; Wed, 3 Jun 2020 16:06:53 +0000 (UTC) Received: from [10.3.113.22] (ovpn-113-22.phx2.redhat.com [10.3.113.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6E41F5C298; Wed, 3 Jun 2020 16:06:50 +0000 (UTC) Subject: Re: [RFC PATCH 2/2] linux-user/mmap: Fix Clang 'type-limit-compare' warning To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <20200503113220.30808-1-f4bug@amsat.org> <20200503113220.30808-3-f4bug@amsat.org> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <7529763d-1f4a-5077-14ed-98753c8db288@redhat.com> Date: Wed, 3 Jun 2020 11:06:50 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200503113220.30808-3-f4bug@amsat.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=eblake@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/03 01:12:11 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: qemu-trivial@nongnu.org, Riku Voipio , Laurent Vivier , Gerd Hoffmann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/3/20 6:32 AM, Philippe Mathieu-Daudé wrote: > When building with Clang 10 on Fedora 32, we get: > > CC linux-user/mmap.o > linux-user/mmap.c:720:49: error: result of comparison 'unsigned long' > 18446744073709551615 is always false [-Werror,-Wtautological-type-limit-compare] > if ((unsigned long)host_addr + new_size > (abi_ulong)-1) { > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~ > > Fix by restricting the check for when target sizeof(abi_ulong) is > smaller than target sizeof(unsigned long). > > Signed-off-by: Philippe Mathieu-Daudé > --- > linux-user/mmap.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/linux-user/mmap.c b/linux-user/mmap.c > index e378033797..b14652d894 100644 > --- a/linux-user/mmap.c > +++ b/linux-user/mmap.c > @@ -714,6 +714,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, > errno = ENOMEM; > host_addr = MAP_FAILED; > } > +#if TARGET_ABI_BITS < TARGET_LONG_BITS > /* Check if address fits target address space */ > if ((unsigned long)host_addr + new_size > (abi_ulong)-1) { Instead of using #if, the following suffices to shut up clang: diff --git c/linux-user/mmap.c w/linux-user/mmap.c index e37803379747..8d9ba201625d 100644 --- c/linux-user/mmap.c +++ w/linux-user/mmap.c @@ -715,7 +715,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, host_addr = MAP_FAILED; } /* Check if address fits target address space */ - if ((unsigned long)host_addr + new_size > (abi_ulong)-1) { + if ((unsigned long)host_addr > (abi_ulong)-1 - new_size) { /* Revert mremap() changes */ host_addr = mremap(g2h(old_addr), new_size, old_size, flags); errno = ENOMEM; That is, it is no longer a tautological type compare if you commute the operations so that neither side is a compile-time constant. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org