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charset="us-ascii" Content-ID: <368925EF85FC6B41886F1D830F44F3B2@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: 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 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: f72a2e69-f66c-4e7e-90fb-08db0481953b X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Feb 2023 18:24:40.3902 (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: hU/OPZeZPQa1EYrDrzG9FgeemGDJ0aW7NfolBN/y5pgVieM+TBLe0fjkShRk78jFXeJqKMcgKvM4Hx4vAyOxrA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR10MB4758 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1 definitions=2023-02-01_04,2023-01-31_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 adultscore=0 suspectscore=0 mlxscore=0 spamscore=0 phishscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2302010158 X-Proofpoint-GUID: 6L8PhIZIhHIztpuVCHOJDMFONNS5yk_h X-Proofpoint-ORIG-GUID: 6L8PhIZIhHIztpuVCHOJDMFONNS5yk_h X-Spam-Status: No, score=-11.5 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,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 Feb 1, 2023, at 11:55 AM, Siddhesh Poyarekar wro= te: >=20 > On 2023-01-31 09:11, Qing Zhao wrote: >> Update documentation to clarify a GCC extension on structure with >> flexible array member being nested in another structure. >> gcc/ChangeLog: >> * doc/extend.texi: Document GCC extension on a structure containing >> a flexible array member to be a member of another structure. >=20 > Should this resolve pr#77650 since the proposed action there appears to b= e to document these semantics? My understanding of pr77650 is specifically for documentation on the follow= ing case: The structure with a flexible array member is the middle field of another s= tructure. Which I added in the documentation as the 2nd situation. =20 However, I am still not very comfortable on my current clarification on thi= s situation: how should we document on=20 the expected gcc behavior to handle such situation? Qing >=20 > Thanks, > Sid >=20 >> --- >> gcc/doc/extend.texi | 35 ++++++++++++++++++++++++++++++++++- >> 1 file changed, 34 insertions(+), 1 deletion(-) >> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi >> index 4a89a3eae7c..54e4baf49a9 100644 >> --- a/gcc/doc/extend.texi >> +++ b/gcc/doc/extend.texi >> @@ -1748,7 +1748,40 @@ Flexible array members may only appear as the las= t member of a >> A structure containing a flexible array member, or a union containing >> such a structure (possibly recursively), may not be a member of a >> structure or an element of an array. (However, these uses are >> -permitted by GCC as extensions.) >> +permitted by GCC as extensions, see details below.) >> +@end itemize >> + >> +GCC extension accepts a structure containing a flexible array member, o= r >> +a union containing such a structure (possibly recursively) to be a memb= er >> +of a structure. >> + >> +There are two situations: >> + >> +@itemize @bullet >> +@item >> +The structure with a flexible array member is the last field of another >> +structure, for example: >> + >> +@smallexample >> +struct flex @{ int length; char data[]; @}; >> + >> +struct out_flex @{ int m; struct flex flex_data; @}; >> +@end smallexample >> + >> +In the above, @code{flex_data.data[]} is considered as a flexible array= too. >> + >> +@item >> +The structure with a flexible array member is the middle field of anoth= er >> +structure, for example: >> + >> +@smallexample >> +struct flex @{ int length; char data[]; @}; >> + >> +struct mid_flex @{ int m; struct flex flex_data; int n; @}; >> +@end smallexample >> + >> +In the above, @code{flex_data.data[]} is allowed to be extended flexibl= y to >> +the padding. E.g, up to 4 elements. >> @end itemize >> Non-empty initialization of zero-length