Re: [PATCH] Input: gpio_keys - replace zero-length array with flexible-array member
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2020-02-14 00:57:27
Also in:
linux-input
On Wed, Feb 12, 2020 at 06:26:00PM -0600, Gustavo A. R. Silva wrote:
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 <redacted>Applied, thank you.
quoted hunk ↗ jump to hunk
--- drivers/input/keyboard/gpio_keys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c index 1f56d53454b2..53c9ff338dea 100644 --- a/drivers/input/keyboard/gpio_keys.c +++ b/drivers/input/keyboard/gpio_keys.c@@ -55,7 +55,7 @@ struct gpio_keys_drvdata { struct input_dev *input; struct mutex disable_lock; unsigned short *keymap; - struct gpio_button_data data[0]; + struct gpio_button_data data[]; }; /*-- 2.23.0
-- Dmitry