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Thread-Topic: [PATCH 2/2] Add a new warning option -Wstrict-flex-arrays. 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charset="us-ascii" Content-ID: <650BFB3986DDE04C9FA5E1DBCEDC2527@namprd10.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: zjxr8c9jieuuJlYUYJwBQ8x8NPhbo99boUqaTJ4iLl6MYe2AwfvF9Aor7w4l1rj6r4dAufjJMz8FavdCSs9uQxlvgqTYR4QM6dvjdAgHu+8B6Br6KLugv7+3TXMSRJU4iio6oBxSTm3wjuZXoIARKZKs7aIkLBnjUAMaV3QvW23f4N35+dCe9Qm3B3oTKn5RqneqmXZuyRY5SO3dbyHTH83g/QD4s1/6e3rVZX6Xe0Uf1LW1eBvff1QAbrlMJklyHZwjzrvIT04i1qIDpVlwTm9KoS1zy32m1GvdUQBJXOIKZifwfYI3fBQbInEE0srGB2cwQeT6GufhBbW6DzCS/rtVqZA3Jf/AicqRUK5aEUqp/0swo90IdKBe3diXuhZOHoQzvTuW1YoUrTEMoRZqFF2a9WGAMEVVDOCnjbeuIHb31mc5PjCaQTIrCTuajf03yzxiRQv7upon5HN0cR3kKME7uIvRJi1DrnNPMMtqHac8HAhslC69vI87K540ngSHbH++N9goMd6B1Q4vepcNjR6gDlRCghIEvxK1Qlv3Br5M6mlZ+/Zob6Cl30LurFBJFyKwMPcaOJWuY/u9F+Ipcgoa9/JWyME8kQ6eE0XDmoVBqWNiB4hcRfhdHzVI58wk+Jxf8He8gMV0VaZjyvaz6IEMIS69kdnOhknwAqYqIB95cY7W83e/HkVSn+Qe+YDMN4bUosPRnHqCA3e80Ghzb5lYKYhM3EetLjJUffzqSPpLeMqYyOVvcgSoGRF1vB40U5mx3RIS56BHZbdkZqHOSPMCJB9cINYVY8SW46RAs7HgqPsNXA6TSAFVa+2tyRIRv5TYhaWG0oWUOaUBxwDVmdXwPxv3NWuzM9wS5XjL4dAem4Uj9IrZRTv39q+JWJzO X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: CH2PR10MB4344.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: d018ee77-c51f-4d13-2324-08dacc935abb X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Nov 2022 14:10:48.0662 (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: lo6wcLMVGk0hDmNKg5XnZ8TgiCSegyk24fZ+PlMBwKmWNWOskHJm+zgSgHokAds7HVIeQqtaqY0CcuXxs6OTtQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BLAPR10MB5265 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-11-22_08,2022-11-18_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 mlxscore=0 suspectscore=0 malwarescore=0 spamscore=0 bulkscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2211220105 X-Proofpoint-GUID: MHhCPnyU1K6t2y6GXBzUv7is9qnWKGtB X-Proofpoint-ORIG-GUID: MHhCPnyU1K6t2y6GXBzUv7is9qnWKGtB X-Spam-Status: No, score=-5.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_SHORT,RCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: > On Nov 22, 2022, at 3:16 AM, Richard Biener wrote: >=20 > On Mon, 21 Nov 2022, Qing Zhao wrote: >=20 >>=20 >>=20 >>> On Nov 18, 2022, at 11:31 AM, Kees Cook wrote: >>>=20 >>> On Fri, Nov 18, 2022 at 03:19:07PM +0000, Qing Zhao wrote: >>>> Hi, Richard, >>>>=20 >>>> Honestly, it?s very hard for me to decide what?s the best way to handl= e the interaction=20 >>>> between -fstrict-flex-array=3DM and -Warray-bounds=3DN.=20 >>>>=20 >>>> Ideally, -fstrict-flex-array=3DM should completely control the behavi= or of -Warray-bounds. >>>> If possible, I prefer this solution. >>>>=20 >>>> However, -Warray-bounds is included in -Wall, and has been used extens= ively for a long time. >>>> It?s not safe to change its default behavior.=20 >>>=20 >>> I prefer that -fstrict-flex-arrays controls -Warray-bounds. That >>> it is in -Wall is _good_ for this reason. :) No one is going to add >>> -fstrict-flex-arrays (at any level) without understanding what it does >>> and wanting those effects on -Warray-bounds. >>=20 >>=20 >> The major difficulties to let -fstrict-flex-arrays controlling -Warray-b= ounds was discussed in the following threads: >>=20 >> https://gcc.gnu.org/pipermail/gcc-patches/2022-October/604133.html >>=20 >> Please take a look at the discussion and let me know your opinion. >=20 > My opinion is now, after re-considering and with seeing your new=20 > patch, that -Warray-bounds=3D2 should be changed to only add > "the intermediate results of pointer arithmetic that may yield out of=20 > bounds values" and that what it considers a flex array should now > be controlled by -fstrict-flex-arrays only. >=20 > That is, I think, the only thing that's not confusing to users even > if that implies a change from previous behavior that we should > document by clarifying the -Warray-bounds documentation as well as > by adding an entry to the Caveats section of gcc-13/changes.html >=20 > That also means that =3D2 will get _less_ warnings with GCC 13 when > the user doesn't use -fstrict-flex-arrays as well. Okay. So, this is for -Warray-bounds=3D2. For -Warray-bounds=3D1 -fstrict-flex-array=3DN, if N > 1, should -fstrict-f= lex-array=3DN control -Warray-bounds=3D1? Qing >=20 > Richard. >=20 > --=20 > Richard Biener > SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg= , > Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; > HRB 36809 (AG Nuernberg)