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dm: replace zero-length array with flexible-array
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 7649773293
("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
parent
bd5c40313a
commit
b18ae8dd9d
9 changed files with 9 additions and 9 deletions
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@ -214,7 +214,7 @@ struct crypt_config {
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struct mutex bio_alloc_lock;
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struct mutex bio_alloc_lock;
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u8 *authenc_key; /* space for keys in authenc() format (if used) */
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u8 *authenc_key; /* space for keys in authenc() format (if used) */
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u8 key[0];
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u8 key[];
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};
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};
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#define MIN_IOS 64
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#define MIN_IOS 64
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@ -92,7 +92,7 @@ struct journal_entry {
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} s;
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} s;
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__u64 sector;
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__u64 sector;
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} u;
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} u;
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commit_id_t last_bytes[0];
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commit_id_t last_bytes[];
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/* __u8 tag[0]; */
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/* __u8 tag[0]; */
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};
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};
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@ -127,7 +127,7 @@ struct pending_block {
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char *data;
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char *data;
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u32 datalen;
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u32 datalen;
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struct list_head list;
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struct list_head list;
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struct bio_vec vecs[0];
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struct bio_vec vecs[];
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};
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};
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struct per_bio_data {
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struct per_bio_data {
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@ -254,7 +254,7 @@ struct raid_set {
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int mode;
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int mode;
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} journal_dev;
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} journal_dev;
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struct raid_dev dev[0];
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struct raid_dev dev[];
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};
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};
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static void rs_config_backup(struct raid_set *rs, struct rs_layout *l)
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static void rs_config_backup(struct raid_set *rs, struct rs_layout *l)
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@ -83,7 +83,7 @@ struct mirror_set {
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struct work_struct trigger_event;
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struct work_struct trigger_event;
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unsigned nr_mirrors;
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unsigned nr_mirrors;
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struct mirror mirror[0];
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struct mirror mirror[];
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};
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};
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DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle,
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DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle,
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@ -56,7 +56,7 @@ struct dm_stat {
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size_t percpu_alloc_size;
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size_t percpu_alloc_size;
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size_t histogram_alloc_size;
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size_t histogram_alloc_size;
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struct dm_stat_percpu *stat_percpu[NR_CPUS];
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struct dm_stat_percpu *stat_percpu[NR_CPUS];
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struct dm_stat_shared stat_shared[0];
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struct dm_stat_shared stat_shared[];
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};
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};
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#define STAT_PRECISE_TIMESTAMPS 1
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#define STAT_PRECISE_TIMESTAMPS 1
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@ -41,7 +41,7 @@ struct stripe_c {
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/* Work struct used for triggering events*/
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/* Work struct used for triggering events*/
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struct work_struct trigger_event;
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struct work_struct trigger_event;
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struct stripe stripe[0];
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struct stripe stripe[];
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};
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};
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/*
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/*
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@ -53,7 +53,7 @@ struct switch_ctx {
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/*
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/*
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* Array of dm devices to switch between.
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* Array of dm devices to switch between.
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*/
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*/
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struct switch_path path_list[0];
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struct switch_path path_list[];
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};
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};
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static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
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static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
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@ -38,7 +38,7 @@ struct node_header {
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struct btree_node {
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struct btree_node {
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struct node_header header;
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struct node_header header;
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__le64 keys[0];
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__le64 keys[];
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} __packed;
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} __packed;
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