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://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 <gustavo@xxxxxxxxxxxxxx>
---
block/partitions/ldm.h | 2 +-
drivers/block/drbd/drbd_int.h | 2 +-
drivers/block/drbd/drbd_protocol.h | 8 ++++----
drivers/block/rbd_types.h | 2 +-
4 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/block/partitions/ldm.h b/block/partitions/ldm.h
index 1ca63e97bccc..172432ce5c0f 100644
--- a/block/partitions/ldm.h
+++ b/block/partitions/ldm.h
@@ -93,7 +93,7 @@ struct frag { /* VBLK Fragment handling */
u8 num; /* Total number of records */
u8 rec; /* This is record number n */
u8 map; /* Which portions are in use */
- u8 data[0];
+ u8 data[];
};
/* In memory LDM database structures. */
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index aae99a2d7bd4..a3314dd781a7 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -620,7 +620,7 @@ struct fifo_buffer {
unsigned int head_index;
unsigned int size;
int total; /* sum of all values */
- int values[0];
+ int values[];
};
extern struct fifo_buffer *fifo_alloc(unsigned int fifo_size);
diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h
index e6fc5ad72501..dea59c92ecc1 100644
--- a/drivers/block/drbd/drbd_protocol.h
+++ b/drivers/block/drbd/drbd_protocol.h
@@ -271,7 +271,7 @@ struct p_rs_param {
u32 resync_rate;
/* Since protocol version 88 and higher. */
- char verify_alg[0];
+ char verify_alg[];
} __packed;
struct p_rs_param_89 {
@@ -305,7 +305,7 @@ struct p_protocol {
u32 two_primaries;
/* Since protocol version 87 and higher. */
- char integrity_alg[0];
+ char integrity_alg[];
} __packed;
@@ -360,7 +360,7 @@ struct p_sizes {
u16 dds_flags; /* use enum dds_flags here. */
/* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */
- struct o_qlim qlim[0];
+ struct o_qlim qlim[];
} __packed;
struct p_state {
@@ -409,7 +409,7 @@ struct p_compressed_bm {
*/
u8 encoding;
- u8 code[0];
+ u8 code[];
} __packed;
struct p_delay_probe93 {
diff --git a/drivers/block/rbd_types.h b/drivers/block/rbd_types.h
index ac98ab6ccd3b..a600e0eb6b6f 100644
--- a/drivers/block/rbd_types.h
+++ b/drivers/block/rbd_types.h
@@ -93,7 +93,7 @@ struct rbd_image_header_ondisk {
__le32 snap_count;
__le32 reserved;
__le64 snap_names_len;
- struct rbd_image_snap_ondisk snaps[0];
+ struct rbd_image_snap_ondisk snaps[];
} __attribute__((packed));
--
2.25.0
