From 23640d641255be9d709c2eddfb0b37ca3c4aeabe Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 2 Mar 2020 06:28:26 -0600
Subject: tehuti: 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>
---
 drivers/net/ethernet/tehuti/tehuti.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'drivers/net/ethernet/tehuti')

diff --git a/drivers/net/ethernet/tehuti/tehuti.h b/drivers/net/ethernet/tehuti/tehuti.h
index 5fc03c8eba0c..909e7296cecf 100644
--- a/drivers/net/ethernet/tehuti/tehuti.h
+++ b/drivers/net/ethernet/tehuti/tehuti.h
@@ -330,7 +330,7 @@ struct txd_desc {
 	u16 length;
 	u32 va_lo;
 	u32 va_hi;
-	struct pbl pbl[0];	/* Fragments */
+	struct pbl pbl[];	/* Fragments */
 } __packed;
 
 /* Register region size */
-- 
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