Re: [PATCH] Input: goldfish_events - Replace zero-length array with flexible-array member

[Dmitry Torokhov]

On Wed, Feb 12, 2020 at 06:24:30PM -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/goldfish_events.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c
> index bc8c85a52a10..57d435fc5c73 100644
> --- a/drivers/input/keyboard/goldfish_events.c
> +++ b/drivers/input/keyboard/goldfish_events.c
> @@ -30,7 +30,7 @@ struct event_dev {
>  	struct input_dev *input;
>  	int irq;
>  	void __iomem *addr;
> -	char name[0];
> +	char name[];
>  };
>  
>  static irqreturn_t events_interrupt(int irq, void *dev_id)
> -- 
> 2.23.0
> 

-- 
Dmitry