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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 6FAF7C433DB for ; Fri, 5 Feb 2021 10:31:05 +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 AF4E464E58 for ; Fri, 5 Feb 2021 10:31:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF4E464E58 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]:55900 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7yOE-0004gP-FD for qemu-devel@archiver.kernel.org; Fri, 05 Feb 2021 05:31:02 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:48744) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7yMM-0003gx-DV for qemu-devel@nongnu.org; Fri, 05 Feb 2021 05:29:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:48672) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7yMI-0005cP-JK for qemu-devel@nongnu.org; Fri, 05 Feb 2021 05:29:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612520940; 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=O5YFFsCbTzkG/E9DkGgKIKl5uxvikkrzrtXZFMa9hY4=; b=Z/kLXFL8jzi3AesMIYsEHGsXubZ48oIG2RrE/z6LXPE7Fm5zPZ7Ayh79pn3wHM8aBNFq44 mPv7PPtPJhgkeVDw1R+Ed13jFz70OywnlS4W4Zjy4atTt4nncdnVPJqWUp2YFlinsTp7ph lJDpn7+Hj2D9ykh1ue5C1qygmYkMiR4= 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-546-R09qnk2XPyiTzRUjSDWMbQ-1; Fri, 05 Feb 2021 05:28:07 -0500 X-MC-Unique: R09qnk2XPyiTzRUjSDWMbQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 569ED1005501; Fri, 5 Feb 2021 10:28:06 +0000 (UTC) Received: from localhost (ovpn-114-98.ams2.redhat.com [10.36.114.98]) by smtp.corp.redhat.com (Postfix) with ESMTP id EB54D722F3; Fri, 5 Feb 2021 10:28:05 +0000 (UTC) Date: Fri, 5 Feb 2021 10:28:05 +0000 From: "Richard W.M. Jones" To: Eric Blake Subject: Re: [PATCH 1/3] utils: Improve qemu_strtosz() to have 64 bits of precision Message-ID: <20210205102805.GA30079@redhat.com> References: <20210204190708.1306296-1-eblake@redhat.com> <20210204190708.1306296-2-eblake@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210204190708.1306296-2-eblake@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=rjones@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=63.128.21.124; envelope-from=rjones@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.351, 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: Kevin Wolf , vsementsov@virtuozzo.com, berrange@redhat.com, qemu-block@nongnu.org, tao3.xu@intel.com, qemu-devel@nongnu.org, armbru@redhat.com, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Feb 04, 2021 at 01:07:06PM -0600, Eric Blake wrote: > We have multiple clients of qemu_strtosz (qemu-io, the opts visitor, > the keyval visitor), and it gets annoying that edge-case testing is > impacted by implicit rounding to 53 bits of precision due to parsing > with strtod(). As an example posted by Rich Jones: > $ nbdkit memory $(( 2**63 - 2**30 )) --run \ > 'build/qemu-io -f raw "$uri" -c "w -P 3 $(( 2**63 - 2**30 - 512 )) 512" ' > write failed: Input/output error > > because 9223372035781033472 got rounded to 0x7fffffffc0000000 which is > out of bounds. > > It is also worth noting that our existing parser, by virtue of using > strtod(), accepts decimal AND hex numbers, even though test-cutils > previously lacked any coverage of the latter. We do have existing > clients that expect a hex parse to work (for example, iotest 33 using > qemu-io -c "write -P 0xa 0x200 0x400"), but strtod() parses "08" as 8 > rather than as an invalid octal number, so we know there are no > clients that depend on octal. Our use of strtod() also means that > "0x1.8k" would actually parse as 1536 (the fraction is 8/16), rather > than 1843 (if the fraction were 8/10); but as this was not covered in > the testsuite, I have no qualms forbidding hex fractions as invalid, > so this patch declares that the use of fractions is only supported > with decimal input, and enhances the testsuite to document that. > > Our previous use of strtod() meant that -1 parsed as a negative; now > that we parse with strtoull(), negative values can wrap around module ^^ modulo The patch looked fine to me although Vladimir found some problems which I didn't spot. I have a question: What happens with leading or trailing whitespace? Is that ignored, rejected or impossible? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v