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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 DB892C2D0A3 for ; Mon, 9 Nov 2020 10:00:35 +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 2547020789 for ; Mon, 9 Nov 2020 10:00:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2547020789 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:47876 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kc3yR-0000zQ-Pp for qemu-devel@archiver.kernel.org; Mon, 09 Nov 2020 05:00:31 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35100) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kc3uN-0005Kt-DR; Mon, 09 Nov 2020 04:56:19 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:2337) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kc3uJ-0006oQ-Ps; Mon, 09 Nov 2020 04:56:19 -0500 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4CV5wX0xCDzkb91; Mon, 9 Nov 2020 17:55:56 +0800 (CST) Received: from [10.174.187.138] (10.174.187.138) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.487.0; Mon, 9 Nov 2020 17:56:05 +0800 Message-ID: <5FA91234.1010708@huawei.com> Date: Mon, 9 Nov 2020 17:56:04 +0800 From: Alex Chen User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Markus Armbruster Subject: Re: [PATCH] qtest: Fix bad printf format specifiers References: <5FA28117.3020802@huawei.com> <67eca43e-99ea-f2ce-5d9e-a9cb5c7a3a83@redhat.com> <5FA38A32.2020008@huawei.com> <18690aa2-3de9-70ad-477f-934724b284a0@redhat.com> <87wnyzouy4.fsf@dusky.pond.sub.org> <1fd5965d-cf5e-b41b-2029-bd3e52c3e498@redhat.com> <8f5ef0b8-4c43-034f-f609-e7e5ca013970@redhat.com> <87d00narns.fsf@dusky.pond.sub.org> In-Reply-To: <87d00narns.fsf@dusky.pond.sub.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.187.138] X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.190; envelope-from=alex.chen@huawei.com; helo=szxga04-in.huawei.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/09 03:21:00 X-ACL-Warn: Detected OS = Linux 3.1-3.10 [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: lvivier@redhat.com, Thomas Huth , QEMU Trivial , QEMU , Paolo Bonzini , =?UTF-8?B?UGhpbGlwcGUgTWF0aGlldS1EYXVk?= =?UTF-8?B?w6k=?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/11/9 15:57, Markus Armbruster wrote: > Thomas Huth writes: > >> On 06/11/2020 15.18, Philippe Mathieu-Daudé wrote: >>> On 11/6/20 7:33 AM, Markus Armbruster wrote: >>>> Thomas Huth writes: >>>> >>>>> On 05/11/2020 06.14, AlexChen wrote: >>>>>> On 2020/11/4 18:44, Thomas Huth wrote: >>>>>>> On 04/11/2020 11.23, AlexChen wrote: >>>>>>>> We should use printf format specifier "%u" instead of "%d" for >>>>>>>> argument of type "unsigned int". >>>>>>>> >>>>>>>> Reported-by: Euler Robot >>>>>>>> Signed-off-by: Alex Chen >>>>>>>> --- >>>>>>>> tests/qtest/arm-cpu-features.c | 8 ++++---- >>>>>>>> 1 file changed, 4 insertions(+), 4 deletions(-) >>>>>>>> [...] >>>>>>>> >>>>>>> >>>>>>> max_vq and vq are both "uint32_t" and not "unsigned int" ... so if you want >>>>>>> to fix this really really correctly, please use PRIu32 from inttypes.h instead. >>>>>>> >>>>>> >>>>>> Hi Thomas, >>>>>> Thanks for your review. >>>>>> According to the definition of the macro PRIu32(# define PRIu32 "u"), >>>>>> using PRIu32 works the same as using %u to print, and using PRIu32 to print >>>>>> is relatively rare in QEMU(%u 720, PRIu32 only 120). Can we continue to use %u to >>>>>> print max_vq and vq in this patch. >>>>>> Of course, this is just my small small suggestion. If you think it is better to use >>>>>> PRIu32 for printing, I will send patch V2. >>>>> >>>>> Well, %u happens to work since "int" is 32-bit with all current compilers >>>>> that we support. >>>> >>>> Yes, it works. >>>> >>>>> But if there is ever a compiler where the size of int is >>>>> different, you'll get a compiler warning here again. >>>> >>>> No, we won't. >>>> >>>> If we ever use a compiler where int is narrower than 32 bits, then the >>>> type of the argument is actually uint32_t[1]. We can forget about this >>>> case, because "int narrower than 32 bits" is not going to fly with our >>>> code base. >> >> Agreed. >> >>>> If we ever use a compiler where int is wider than 32 bits, then the type >>>> of the argument is *not* uint32_t[2]. PRIu32 will work anyway, because >>>> it will actually retrieve an unsigned int argument, *not* an uint32_t >>>> argument[3]. >> >> I can hardly believe that this can be true. Sure, it's true for such cases >> like this one here, where you multiply with an "int". But if you just try to >> print a plain uint32_t variable? > > Default argument promotions (§6.5.2.2 Function calls) still apply: "the > integer promotions are performed on each argument, and arguments that > have type float are promoted to double." > >> I've seen compiler warning in cases one tries to print a 16-bit (i.e. short) >> variable in the past if you use %d instead of the proper PRId16 (or %hd) >> format specifier - maybe not on x86, but certainly on other architectures. >> If you're statement was right, that should not have happened, should it? > > §7.19.6.1 "The fprintf function" on length modifier 'h': > > Specifies that a following d, i, o, u, x, or X conversion specifier > applies to a short int or unsigned short int argument (the argument > will have been promoted according to the integer promotions, but its > value shall be converted to short int or unsigned short int before > printing) > > Integer promotions preserve value including sign. So, printing a short > value with %hd first promotes it to int, then converts it back to short. > Neither conversion has an effect. > > However, printing an int with %hd has: it converts int to short. > Implementation-defined behavior when the value doesn't fit. > > Length modifier 'h' is pretty pointless with printf(). So would be a > warning to nudge people towards its use. > > In fact, GNU libc's PRIu32 does not use it. inttypes.h: > > /* Unsigned integers. */ > # define PRIu8 "u" > # define PRIu16 "u" > # define PRIu32 "u" > # define PRIu64 __PRI64_PREFIX "u" > > where __PRI64_PREFIX is "l" or "ll" depending on system-dependent > __WORDSIZE. > > In short: > >>>> In other words "%" PRIu32 is just a less legible alias for "%u" in all >>>> cases that matter. > Hi Markus, Thanks for your reply, I have learned a lot. May I understand it as follows: %u is used when there are parameters obtained by arithmetic operation; otherwise, PRIu32 is used to print uint32_t type parameters? Thanks, Alex