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From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Jean Delvare <jdelvare@suse.com>, Guenter Roeck <linux@roeck-us.net>
Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] hwmon: (ibmaem) Replace zero-length array with flexible-array member
Date: Tue, 11 Feb 2020 17:42:37 -0600
Message-ID: <20200211234237.GA26971@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
inadvertenly introduced[3] to the codebase from now on.

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>
---
 drivers/hwmon/ibmaem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/ibmaem.c b/drivers/hwmon/ibmaem.c
index db63c1295cb2..fb052c2d9c34 100644
--- a/drivers/hwmon/ibmaem.c
+++ b/drivers/hwmon/ibmaem.c
@@ -232,7 +232,7 @@ struct aem_read_sensor_req {
 
 struct aem_read_sensor_resp {
 	struct aem_iana_id	id;
-	u8			bytes[0];
+	u8			bytes[];
 } __packed;
 
 /* Data structures to talk to the IPMI layer */
-- 
2.25.0


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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 23:42 Gustavo A. R. Silva [this message]
2020-02-12 20:45 ` Guenter Roeck

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