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Message-ID: Date: Fri, 7 Jul 2023 11:46:19 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [XEN PATCH v2 12/13] xen/x86: fix violations of MISRA C:2012 Rule 7.2 Content-Language: en-US To: Simone Ballarin Cc: consulting@bugseng.com, Gianluca Luparini , Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , Paul Durrant , Stefano Stabellini , Michal Orzel , Xenia Ragiadakou , Ayan Kumar Halder , xen-devel@lists.xenproject.org References: From: Jan Beulich In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: FR2P281CA0150.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:98::11) To DU2PR04MB8790.eurprd04.prod.outlook.com (2603:10a6:10:2e1::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DU2PR04MB8790:EE_|AM0PR04MB7058:EE_ X-MS-Office365-Filtering-Correlation-Id: 9f8726f2-7f4d-4ca9-3602-08db7ecf05cf X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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There is no way the lapic >>>>>>> * can underflow in the 100ms detection time frame. >>>>>>> */ >>>>>>> - __setup_APIC_LVTT(0xffffffff); >>>>>>> + __setup_APIC_LVTT(0xffffffffU); >>>>>> >>>>>> While making the change less mechanical, we want to consider to switch >>>>>> to ~0 in this and similar cases. >>>>>> >>>>> >>>>> Changing ~0U is more than not mechanical: it is possibly dangerous. >>>>> The resulting value could be different depending on the architecture, >>>>> I prefer to not make such kind of changes in a MISRA-related patch. >>>> >>>> What do you mean by "depending on the architecture", when this is >>>> x86-only code _and_ you can check what type parameter the called >>>> function has? >>> >>> Ok, I will change these literals in ~0U in the next submission. >> >> Except that I specifically meant ~0, not ~0U. We mean "maximum value" >> here, and at the call site it doesn't matter how wide the function >> parameter's type is. If it was 64-bit, ~0U would not do what is wanted. > > ~0 is not a MISRA-compliant solution since bitwise operations on signed > integers have implementation-defined behavior. This solution definitively > violates Rule 10.1. So if we adopted that rule (we didn't so far), we'd have to e.g. change all literal number shift counts to have U suffixes, no matter that without the suffix it is still entirely obvious that the numbers are unsigned? I'm afraid that'll face my opposition ... Jan