On Fri, Feb 14, 2020 at 11:20:22AM -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 <gustavo@xxxxxxxxxxxxxx>
Applied, thank you.
> ---
> drivers/input/keyboard/tca6416-keypad.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/input/keyboard/tca6416-keypad.c b/drivers/input/keyboard/tca6416-keypad.c
> index 2a14769de637..21758767ccf0 100644
> --- a/drivers/input/keyboard/tca6416-keypad.c
> +++ b/drivers/input/keyboard/tca6416-keypad.c
> @@ -33,7 +33,7 @@ MODULE_DEVICE_TABLE(i2c, tca6416_id);
>
> struct tca6416_drv_data {
> struct input_dev *input;
> - struct tca6416_button data[0];
> + struct tca6416_button data[];
> };
>
> struct tca6416_keypad_chip {
> @@ -48,7 +48,7 @@ struct tca6416_keypad_chip {
> int irqnum;
> u16 pinmask;
> bool use_polling;
> - struct tca6416_button buttons[0];
> + struct tca6416_button buttons[];
> };
>
> static int tca6416_write_reg(struct tca6416_keypad_chip *chip, int reg, u16 val)
> --
> 2.25.0
>
--
Dmitry
