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From: "Gustavo A. R. Silva" <>
To: Dan Williams <>, Vinod Koul <>
	"Gustavo A. R. Silva" <>
Subject: [PATCH] dmaengine: sa11x0: Replace zero-length array with flexible-array member
Date: Fri, 14 Feb 2020 11:14:35 -0600
Message-ID: <20200214171435.GA22930@embeddedor> (raw)

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.

[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <>
 drivers/dma/sa11x0-dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/sa11x0-dma.c b/drivers/dma/sa11x0-dma.c
index afb68055ed1b..0fa7f14a65a1 100644
--- a/drivers/dma/sa11x0-dma.c
+++ b/drivers/dma/sa11x0-dma.c
@@ -78,7 +78,7 @@ struct sa11x0_dma_desc {
 	bool			cyclic;
 	unsigned		sglen;
-	struct sa11x0_dma_sg	sg[0];
+	struct sa11x0_dma_sg	sg[];
 struct sa11x0_dma_phy;

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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 17:14 Gustavo A. R. Silva [this message]
2020-02-19 12:19 ` Vinod Koul

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