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R. Silva" To: Mark Fasheh , Joel Becker , Joseph Qi Message-ID: <20200309202155.GA8432@embeddedor> Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - oss.oracle.com X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-L: No X-Exim-ID: 1jBOrK-000xqo-O9 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.168.201]:19736 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 14 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes MIME-Version: 1.0 X-PDR: PASS X-Source-IP: 192.185.66.3 X-ServerName: gateway20.websitewelcome.com X-Proofpoint-SPF-Result: pass X-Proofpoint-SPF-Record: v=spf1 a mx +ip4:108.167.133.22 +ip4:192.185.0.0/16 include:websitewelcome.com ~all X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9555 signatures=668685 X-Proofpoint-Spam-Details: rule=tap_spam_policies_notspam policy=tap_spam_policies score=0 malwarescore=0 phishscore=0 lowpriorityscore=0 priorityscore=0 suspectscore=0 mlxlogscore=797 impostorscore=0 adultscore=0 mlxscore=0 clxscore=176 bulkscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003090124 X-Spam: Clean X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 spamscore=0 bulkscore=0 mlxscore=0 suspectscore=0 mlxlogscore=999 phishscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003090125 Cc: linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, "Gustavo A. R. Silva" Subject: [Ocfs2-devel] [PATCH][next] ocfs2: ocfs2_fs.h: Replace zero-length array with flexible-array member X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9555 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 mlxscore=0 mlxlogscore=999 spamscore=0 suspectscore=0 adultscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003090125 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9555 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 impostorscore=0 mlxlogscore=999 suspectscore=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 adultscore=0 spamscore=0 mlxscore=0 clxscore=1034 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003090125 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: struct foo { int stuff; struct boo array[]; }; 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. Also, notice that, dynamic memory allocations won't be affected by this change: "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] This issue was found with the help of Coccinelle. [1] https://urldefense.com/v3/__https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html__;!!GqivPVa7Brio!OKPotRhYhHbCG2kibo8Q6_6CuKaa28d_74h1svxyR6rbshrK2L_BdrQpNbvJWBWb40QCkg$ [2] https://urldefense.com/v3/__https://github.com/KSPP/linux/issues/21__;!!GqivPVa7Brio!OKPotRhYhHbCG2kibo8Q6_6CuKaa28d_74h1svxyR6rbshrK2L_BdrQpNbvJWBUhNn9M6g$ [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Acked-by: Joseph Qi --- fs/ocfs2/ocfs2_fs.h | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h index 0db4a7ec58a2..0dd8c41bafd4 100644 --- a/fs/ocfs2/ocfs2_fs.h +++ b/fs/ocfs2/ocfs2_fs.h @@ -470,7 +470,7 @@ struct ocfs2_extent_list { __le16 l_reserved1; __le64 l_reserved2; /* Pad to sizeof(ocfs2_extent_rec) */ -/*10*/ struct ocfs2_extent_rec l_recs[0]; /* Extent records */ +/*10*/ struct ocfs2_extent_rec l_recs[]; /* Extent records */ }; /* @@ -484,7 +484,7 @@ struct ocfs2_chain_list { __le16 cl_count; /* Total chains in this list */ __le16 cl_next_free_rec; /* Next unused chain slot */ __le64 cl_reserved1; -/*10*/ struct ocfs2_chain_rec cl_recs[0]; /* Chain records */ +/*10*/ struct ocfs2_chain_rec cl_recs[]; /* Chain records */ }; /* @@ -496,7 +496,7 @@ struct ocfs2_truncate_log { /*00*/ __le16 tl_count; /* Total records in this log */ __le16 tl_used; /* Number of records in use */ __le32 tl_reserved1; -/*08*/ struct ocfs2_truncate_rec tl_recs[0]; /* Truncate records */ +/*08*/ struct ocfs2_truncate_rec tl_recs[]; /* Truncate records */ }; /* @@ -640,7 +640,7 @@ struct ocfs2_local_alloc __le16 la_size; /* Size of included bitmap, in bytes */ __le16 la_reserved1; __le64 la_reserved2; -/*10*/ __u8 la_bitmap[0]; +/*10*/ __u8 la_bitmap[]; }; /* @@ -653,7 +653,7 @@ struct ocfs2_inline_data * for data, starting at id_data */ __le16 id_reserved0; __le32 id_reserved1; - __u8 id_data[0]; /* Start of user data */ + __u8 id_data[]; /* Start of user data */ }; /* @@ -798,7 +798,7 @@ struct ocfs2_dx_entry_list { * possible in de_entries */ __le16 de_num_used; /* Current number of * de_entries entries */ - struct ocfs2_dx_entry de_entries[0]; /* Indexed dir entries + struct ocfs2_dx_entry de_entries[]; /* Indexed dir entries * in a packed array of * length de_num_used */ }; @@ -935,7 +935,7 @@ struct ocfs2_refcount_list { __le16 rl_used; /* Current number of used records */ __le32 rl_reserved2; __le64 rl_reserved1; /* Pad to sizeof(ocfs2_refcount_record) */ -/*10*/ struct ocfs2_refcount_rec rl_recs[0]; /* Refcount records */ +/*10*/ struct ocfs2_refcount_rec rl_recs[]; /* Refcount records */ }; @@ -1021,7 +1021,7 @@ struct ocfs2_xattr_header { buckets. A block uses xb_check and sets this field to zero.) */ - struct ocfs2_xattr_entry xh_entries[0]; /* xattr entry list. */ + struct ocfs2_xattr_entry xh_entries[]; /* xattr entry list. */ }; /* @@ -1207,7 +1207,7 @@ struct ocfs2_local_disk_dqinfo { /* Header of one chunk of a quota file */ struct ocfs2_local_disk_chunk { __le32 dqc_free; /* Number of free entries in the bitmap */ - __u8 dqc_bitmap[0]; /* Bitmap of entries in the corresponding + __u8 dqc_bitmap[]; /* Bitmap of entries in the corresponding * chunk of quota file */ };