linux-kernel - [PATCH] amba: tegra-ahb: Replace zero-length array with flexible-array member

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Message-ID: <20200211210213.GA28043@embeddedor>
Date:   Tue, 11 Feb 2020 15:02:13 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Russell King <linux@...linux.org.uk>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] amba: tegra-ahb: 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
inadvertenly introduced[3] to the codebase from now on.

[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@...eddedor.com>
---
 drivers/amba/tegra-ahb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/amba/tegra-ahb.c b/drivers/amba/tegra-ahb.c
index b0b688c481e8..e9e5c7bb580c 100644
--- a/drivers/amba/tegra-ahb.c
+++ b/drivers/amba/tegra-ahb.c
@@ -129,7 +129,7 @@ static const u32 tegra_ahb_gizmo[] = {
 struct tegra_ahb {
 	void __iomem	*regs;
 	struct device	*dev;
-	u32		ctx[0];
+	u32		ctx[];
 };
 
 static inline u32 gizmo_readl(struct tegra_ahb *ahb, u32 offset)
-- 
2.25.0