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R. Silva" , KY Srinivasan , Haiyang Zhang , Stephen Hemminger , Sasha Levin , Lorenzo Pieralisi , Andrew Murray , Bjorn Helgaas CC: "linux-hyperv@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] PCI: hv: Replace zero-length array with flexible-array member Thread-Topic: [PATCH] PCI: hv: Replace zero-length array with flexible-array member Thread-Index: AQHV4gsYucMpvat5UUSDAQTTiNi7uKgYdpbQ Date: Thu, 13 Feb 2020 03:43:40 +0000 Message-ID: References: <20200213005048.GA9662@embeddedor.com> In-Reply-To: <20200213005048.GA9662@embeddedor.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Owner=decui@microsoft.com; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2020-02-13T03:43:39.3474924Z; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=General; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Application=Microsoft Azure Information Protection; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=d08b85ce-1d8f-49a6-889f-41446c59405c; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Extended_MSFT_Method=Automatic authentication-results: spf=none (sender IP is ) smtp.mailfrom=decui@microsoft.com; x-originating-ip: [2601:600:a280:7f70:c129:4d3:3571:d407] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 4606557a-eba4-4e46-f2fb-08d7b036eb03 x-ms-traffictypediagnostic: HK0P153MB0292:|HK0P153MB0292: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:10000; x-forefront-prvs: 031257FE13 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(4636009)(376002)(346002)(39860400002)(366004)(396003)(136003)(199004)(189003)(86362001)(316002)(81166006)(7696005)(8676002)(71200400001)(186003)(54906003)(8936002)(110136005)(81156014)(2906002)(66946007)(478600001)(4326008)(33656002)(6506007)(10290500003)(66476007)(9686003)(76116006)(66556008)(55016002)(66446008)(64756008)(5660300002)(8990500004)(52536014);DIR:OUT;SFP:1102;SCL:1;SRVR:HK0P153MB0292;H:HK0P153MB0148.APCP153.PROD.OUTLOOK.COM;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: microsoft.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: YSE02fdnMPCXUG62qEdDjJ0uONQgagRNo2hOKPEV/MLAE1JsEqDuADeT89ewcEjlyXpWnEXD0I5Goc7JlHVTt7+54Z5OVuwGCYBroEOxt2/8Rti0V0Zw/PkZ0soxCmrlPRdxHuneVBnvP0gagm0LcX1e1txYLPkfYyKmtZhdYgMvTJ0TIXQw5eIYMJtgWkgr2ADrRL5E6iRSMKcgT2huYfU+BKlTU5taLIFCo3K1SSu/qf4Gg/n19KqqOsWkRVTxxvDvBgdOtI7gRawXKEC6rKd63CGB/CqdwRxo7iDDKEYke4/3attlGr1ZbHqMU3FENBF/oKnELDv2HpMagXeq1IvFnW7W2ldQ0fqUL/s0xjbzda+L0g4+KhSJVuZWo0BQJrA5Kcap8+Y19kbwriLt/Ht+AZpGJ1nTC0/iiF27S7Eh7JWV6A6/rSUvBCNKGPmv x-ms-exchange-antispam-messagedata: C6SRptTY+1NYk3NMp4rBVKap3aWX5FSM9mq8M04jH1+rnWlV+Z6tp2+Xpof7hkXhsKdlEi0gb7xMrCGErm8et+RUA22bvaPp7KZMjM4pK6i0dwxSdiy7xKg81cBGmfW4QyP09yBM+OK0QVA7I0qOWakamtVlOanTFSO+G1ZwkCh9cENu9DDsA9lkD1wSWDboEbAJvf9oHD0z6hfjbDxKUw== Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4606557a-eba4-4e46-f2fb-08d7b036eb03 X-MS-Exchange-CrossTenant-originalarrivaltime: 13 Feb 2020 03:43:40.9674 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 0RB9BCpfTZOnsZXet7cJAV1ddN6XmbzFnq2MTgtrriizcK6njOEChJa+i6J9kpGHnBQuiasTCzlxfemUWFsIiA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: HK0P153MB0292 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org > From: linux-hyperv-owner@vger.kernel.org > On Behalf Of Gustavo A. R. Silva > Sent: Wednesday, February 12, 2020 4:51 PM > ... > The current codebase makes use of the zero-length array language > extension to the C90 standard, but the preferred mechanism to declare > variable-length types such as these ones is a flexible array member[1][2]= , > introduced in C99: >=20 > struct foo { > int stuff; > struct boo array[]; > }; >=20 > By making use of the mechanism above, we will get a compiler warning > in case the flexible array does not occur last in the structure, which > will help us prevent some kind of undefined behavior bugs from being > inadvertently introduced[3] to the codebase from now on. >=20 > Also, notice that, dynamic memory allocations won't be affected by > this change: >=20 > "Flexible array members have incomplete type, and so the sizeof operator > may not be applied. As a quirk of the original implementation of > zero-length arrays, sizeof evaluates to zero."[1] >=20 > This issue was found with the help of Coccinelle. Looks good to me. Thanks, Gustavo! =20 Reviewed-by: Dexuan Cui FWIW, it looks there are a lot of more to fix in the kernel tree: the below commands return 1373 for me: grep -nr '\[0\];$' * | grep '\.h:' | grep -v =3D | wc -l Running the commands against the kernel/ directory returns 3. Thanks, -- Dexuan