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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Tue, 18 Feb 2020 10:25:08 +0900
Message-ID: <CAK7LNASABqhpCjoQkQAZAVOjTvVG+4PDWaP+a8=hcv6GsgeQMQ@mail.gmail.com>
Subject: Re: [PATCH] gpio: uniphier: Replace zero-length array with
 flexible-array member
To:     "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Feb 12, 2020 at 6:03 AM Gustavo A. R. Silva
<gustavo@embeddedor.com> 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
> 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>

Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>


> ---
>  drivers/gpio/gpio-uniphier.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-uniphier.c b/drivers/gpio/gpio-uniphier.c
> index 0f662b297a95..9843638d99d0 100644
> --- a/drivers/gpio/gpio-uniphier.c
> +++ b/drivers/gpio/gpio-uniphier.c
> @@ -33,7 +33,7 @@ struct uniphier_gpio_priv {
>         struct irq_domain *domain;
>         void __iomem *regs;
>         spinlock_t lock;
> -       u32 saved_vals[0];
> +       u32 saved_vals[];
>  };
>
>  static unsigned int uniphier_gpio_bank_to_reg(unsigned int bank)
> --
> 2.25.0
>


-- 
Best Regards
Masahiro Yamada