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Message-ID: <2c8c246d-caea-5c8b-4a2a-83248422c48d@suse.com> Date: Wed, 8 Nov 2023 12:19:27 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [XEN PATCH][for-4.19] domain: add ASSERT to help static analysis tools Content-Language: en-US To: Nicola Vetrini Cc: sstabellini@kernel.org, michal.orzel@amd.com, xenia.ragiadakou@amd.com, ayan.kumar.halder@amd.com, consulting@bugseng.com, andrew.cooper3@citrix.com, roger.pau@citrix.com, George Dunlap , Julien Grall , Wei Liu , xen-devel@lists.xenproject.org References: <3f163bb58993410183229e72eb1f227057f9b1c7.1699034273.git.nicola.vetrini@bugseng.com> <44df74cb532bfb9642b1c8752ee8c0d6@bugseng.com> From: Jan Beulich In-Reply-To: <44df74cb532bfb9642b1c8752ee8c0d6@bugseng.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: FR0P281CA0049.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:48::15) To DU2PR04MB8790.eurprd04.prod.outlook.com (2603:10a6:10:2e1::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DU2PR04MB8790:EE_|DB9PR04MB8155:EE_ X-MS-Office365-Filtering-Correlation-Id: ba1f9722-58e9-4dc8-7b57-08dbe04c9375 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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This ASSERT helps them in >>> detecting that such a condition is not possible >>> and also provides a basic sanity check. >> >> I disagree with this being a possible justification for adding such a >> redundant assertion. More detail is needed on what is actually >> (suspected to be) confusing the tool. Plus it also needs explaining >> why (a) adding such an assertion helps and (b) how that's going to >> cover release builds. >> > > How about: > "Static analysis tools may detect a possible null pointer dereference > at line 760 (config->handle) due to config possibly being NULL. > > However, given that all system domains, including IDLE, have a NULL > config and in the code path leading to the assertion only real domains > (which have a non-NULL config) can be present." > > On point b): this finding is a false positive, therefore even if the > ASSERT is > expanded to effectively a no-op, there is no inherent problem with Xen's > code. > The context in which the patch was suggested [1] hinted at avoiding > inserting in > the codebase false positive comments. Which I largely agree with. What I don't agree with is adding an assertion which is only papering over the issue, and only in debug builds. So perhaps instead we need a different way of tracking false positives (which need to be tied to specific checker versions anyway). Jan