scsi: Replace zero-length array with flexible-array member

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")

Link: https://lore.kernel.org/r/20200224161406.GA21454@embeddedor
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/scsi/mvsas/mv_sas.h b/drivers/scsi/mvsas/mv_sas.h
index 519edc796691..327fdd5ee962 100644
--- a/drivers/scsi/mvsas/mv_sas.h
+++ b/drivers/scsi/mvsas/mv_sas.h
@@ -394,7 +394,7 @@ struct mvs_info {
 	dma_addr_t bulk_buffer_dma1;
 #define TRASH_BUCKET_SIZE    	0x20000
 	void *dma_pool;
-	struct mvs_slot_info slot_info[0];
+	struct mvs_slot_info slot_info[];
 };
 
 struct mvs_prv_info{