Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 31 Mar 2022 11:14:10 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     David Gow <davidgow@google.com>
Cc:     Marcelo Schmitt <marcelo.schmitt1@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Daniel Latypov <dlatypov@google.com>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        linux-sparse@vger.kernel.org, cocci@inria.fr,
        smatch@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Shuah Khan <skhan@linuxfoundation.org>, julia.lawall@inria.fr
Subject: Re: [PATCH v2 2/2] Documentation: dev-tools: Enhance static analysis
 section with discussion
Message-ID: <20220331081409.GY12805@kadam>
References: <cover.1648593132.git.marcelo.schmitt1@gmail.com>
 <11f4750c6d4c175994dfd36d1ff385f68f61bd02.1648593132.git.marcelo.schmitt1@gmail.com>
 <CABVgOSkb5CpnXDF_m7iy=A7RmN+KmY0T38TeZ4hKbmkdQgt6Yw@mail.gmail.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CABVgOSkb5CpnXDF_m7iy=A7RmN+KmY0T38TeZ4hKbmkdQgt6Yw@mail.gmail.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?2wqaQw5/ep0g1M3lTV6HpEqNIbTqVnFtxi20+338QMilbWymwfai/joWnXT6?=
 =?us-ascii?Q?zIeZYNYfY2yzupqbrbtDZaalXM4ObXhF7RSSop37gLOFBCOYEURlqaC9T9AS?=
 =?us-ascii?Q?3DR9YzkXJCeOsNAMO73hFKtHZIDwo5FXJQFgMdDm/iBvGEvMcY5s4k29MZTR?=
 =?us-ascii?Q?RMEIe5xO7rlxO3xRo8HMLpI+qN5WvRMdFdRfLx+nBv0uR6qMrBd7nAlNG6zN?=
 =?us-ascii?Q?lME1v95IUPvH4MB13aXpccuGgaALFfbFR1EYfZB8YjciePbPTwSP2pcXQwfR?=
 =?us-ascii?Q?xBQjhXvYabL/gb5fpTFReDtKEQ9B+hW9L5QRct17tABqYZhlLupj1PJuvcAw?=
 =?us-ascii?Q?oS3RRA1/RsaPq5TyvGI89XW76BbgXha2aH48pSP1w/zt4UqKFqUoysFElFKl?=
 =?us-ascii?Q?7Bsa+hFdbHmTOGD8Ex6p/vx6CZuFU1wMthFOyD9ILnjxDwbWIWyV5GDaMp6z?=
 =?us-ascii?Q?/mIL5CyG94CipPqGbF/D7Tqn5kYl1P+D/39mLbdr0elfZkaaHnv8uXWXx72W?=
 =?us-ascii?Q?l+CLSKse96zZrC1XQVTTYv9dAvi1dqtyRnVxEN5fPrWT0VYDQC9O9ojieq9z?=
 =?us-ascii?Q?5eZ11VEOO8L72OXvk6/OpvSh2rxKYvOSfRSpymSXQYEs/24tElLWT8B6lSDp?=
 =?us-ascii?Q?gBdwQZL4dMcWvoIaPTkVegIw/cYoIUuKj6l7BR2tbL9nC/OTTena981mv88Y?=
 =?us-ascii?Q?ZPc5S1JUXySho9CEgQUPx5QiBeshIhzmwUU/BOAJpfjZY4EPWubWu1DTZKCN?=
 =?us-ascii?Q?3KvO45c7DF83mOjgSQoLcrI5oHhEqTBm5t6kSoBzMzE3jQ+LOfLq+14ArHqh?=
 =?us-ascii?Q?9LJ3OcB+IOarp9ifrtDqS2an83EYtaSD5WUlPIepNDiJlT3EgHbixzSyYFKG?=
 =?us-ascii?Q?BBxSQGi5JSyJHbrAsTr9VBzu5yuxp+fkK6TiTQGC8JMxS+mduV2AqfRN1yaS?=
 =?us-ascii?Q?Gx3J8k66RBobv+79U250klXZX56hmOxb05HxsjIRcJwvifOZQIV1D8coY8LW?=
 =?us-ascii?Q?4vqQk/V/aVRs3LwuMP+5Zso4qc/uBswqUUVfskOytzFgu6AqQKJm5KDAa7wM?=
 =?us-ascii?Q?4kTfVXqmpUTYrkjpuwPsbEsYQOY8Ic2qu/hLUvCVD2eVHzOvWL7RoIUacMNj?=
 =?us-ascii?Q?/D/JcZhjQE1qFkn1NdWC9DLSWZuM1zNftE+zKBiZYjHxsT6a7mZ5Jvr8SBcT?=
 =?us-ascii?Q?n5z3eSTSsYALB0FsQMEiMgGJMzYreRAADiKsBcgMUVugTqEcD4l3QtzQzBN7?=
 =?us-ascii?Q?J2X6FJ8MZ6xwPnTDchxLg85edFmbzCrxvEH/tVI4UXx28WkloM5ALAuYrPCI?=
 =?us-ascii?Q?NJI4M9qP+vp7fMz0/tZayXEjYdrG+S4ZcSWyX8YcjD/jU9aznrIO3Yc0udpN?=
 =?us-ascii?Q?zJ4TMvWm950kgeLTW+exQ+uzMMfQHYcHpzRHxN1JQxKwqVBgbgdxzwDLlBRb?=
 =?us-ascii?Q?wAEcp/ZhrS/ltg2JpkEZKrh7gqc+0piOCG5JltlqtJGOo1fxrrNxK1TcWKhH?=
 =?us-ascii?Q?yRmnBLDsvBSzpkTJYaVTDFfX0rYchj8d0gXiYUcBAoNUSrOTYuXKAcdCBDJZ?=
 =?us-ascii?Q?WU4o55LlGhenJKUn7U1DRjQX7JaTldXwdcM5NckZhBxOxafEEzEUPtzeoRGK?=
 =?us-ascii?Q?ahNlVsCmYSVd5MrvpG9ivukBQ2js8uU0nXlcpqbLUGnKS2kGWw/CWus4eEvm?=
 =?us-ascii?Q?J7xLsKSA/eNSHMOep67a8KOgidMD5xyR0BkQ34JhwjzQXEAabIbxVxbhQBpP?=
 =?us-ascii?Q?IGeUMzQlZYWutEhx0Isrpn/6SyOU/OI=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: aa49396f-e3b7-4d41-9416-08da12ee7632
X-MS-Exchange-CrossTenant-AuthSource: MWHPR1001MB2365.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Mar 2022 08:14:22.4326
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: LbxbJbjzcG81nOYdorxr2rFcLqiya/PWssueqPKYkW/mvHdnRYfzqIyqRMyqujSuTlXahvyg+6zr6NadDEVGFNQ2fihXCD7lQLxE5UIguQ8=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN8PR10MB3508
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.425,18.0.850
 definitions=2022-03-31_03:2022-03-29,2022-03-31 signatures=0
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=999
 phishscore=0 malwarescore=0 bulkscore=0 suspectscore=0 adultscore=0
 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2202240000 definitions=main-2203310045
X-Proofpoint-ORIG-GUID: qHsypwRQde9I_185KKpu-b7QVC0_Zfn0
X-Proofpoint-GUID: qHsypwRQde9I_185KKpu-b7QVC0_Zfn0
X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, Mar 30, 2022 at 10:48:13AM +0800, David Gow wrote:
> > +
> > +Smatch does flow analysis and, if allowed to build the function database, it
> > +also does cross function analysis. Smatch tries to answer questions like where
> > +is this buffer allocated? How big is it? Can this index be controlled by the
> > +user? Is this variable larger than that variable?
> > +
> > +It's generally easier to write checks in Smatch than it is to write checks in
> > +Sparse. Nevertheless, there are some overlaps between Sparse and Smatch checks
> > +because there is no reason for re-implementing Sparse's check in Smatch.
> 
> This last sentence isn't totally clear to me. Should this "because" be "so"?
> 

I stopped reading your email when you wrote "Cheers, David" but I should
have scrolled down.

There is not very much overlap between Sparse and Smatch.  Both have a
warning for if (!x & y).  That is a tiny thing.  The big overlap is when
it comes to the locking checks.  The Smatch check for locking is
honestly way better and more capable.

I always run both Sparse and Smatch on my patches.  I should run
Coccinelle as well, but I'm more familiar with Sparse and Smatch.

regards,
dan carpenter