chelsio: 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")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.h b/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.h
index 7b02c200dd1e..1b4156461ba1 100644
--- a/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.h
+++ b/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.h
@@ -122,7 +122,7 @@ struct cxgbi_ppm_pool {
 	unsigned int base;		/* base index */
 	unsigned int next;		/* next possible free index */
 	spinlock_t lock;		/* ppm pool lock */
-	unsigned long bmap[0];
+	unsigned long bmap[];
 } ____cacheline_aligned_in_smp;
 
 struct cxgbi_ppm {
@@ -145,7 +145,7 @@ struct cxgbi_ppm {
 	unsigned int next;
 	unsigned int max_index_in_edram;
 	unsigned long *ppod_bmap;
-	struct cxgbi_ppod_data ppod_data[0];
+	struct cxgbi_ppod_data ppod_data[];
 };
 
 #define DDP_THRESHOLD		512