On 2/13/20 1:02 AM, Gustavo A. R. Silva wrote:
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> --- drivers/scsi/advansys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c index a242a62caaa1..c2c7850ff7b4 100644 --- a/drivers/scsi/advansys.c +++ b/drivers/scsi/advansys.c @@ -316,7 +316,7 @@ typedef struct asc_sg_head { ushort queue_cnt; ushort entry_to_copy; ushort res; - ASC_SG_LIST sg_list[0]; + ASC_SG_LIST sg_list[]; } ASC_SG_HEAD;typedef struct asc_scsi_q {
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