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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit
76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
struct mutex bio_alloc_lock;
u8 *authenc_key; /* space for keys in authenc() format (if used) */
- u8 key[0];
+ u8 key[];
};
#define MIN_IOS 64
} s;
__u64 sector;
} u;
- commit_id_t last_bytes[0];
+ commit_id_t last_bytes[];
/* __u8 tag[0]; */
};
char *data;
u32 datalen;
struct list_head list;
- struct bio_vec vecs[0];
+ struct bio_vec vecs[];
};
struct per_bio_data {
int mode;
} journal_dev;
- struct raid_dev dev[0];
+ struct raid_dev dev[];
};
static void rs_config_backup(struct raid_set *rs, struct rs_layout *l)
struct work_struct trigger_event;
unsigned nr_mirrors;
- struct mirror mirror[0];
+ struct mirror mirror[];
};
DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle,
size_t percpu_alloc_size;
size_t histogram_alloc_size;
struct dm_stat_percpu *stat_percpu[NR_CPUS];
- struct dm_stat_shared stat_shared[0];
+ struct dm_stat_shared stat_shared[];
};
#define STAT_PRECISE_TIMESTAMPS 1
/* Work struct used for triggering events*/
struct work_struct trigger_event;
- struct stripe stripe[0];
+ struct stripe stripe[];
};
/*
/*
* Array of dm devices to switch between.
*/
- struct switch_path path_list[0];
+ struct switch_path path_list[];
};
static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
struct btree_node {
struct node_header header;
- __le64 keys[0];
+ __le64 keys[];
} __packed;