linux-kernel - Re: [PATCH] amba: tegra-ahb: Replace zero-length array with flexible-array member

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Message-ID: <292f9b65-c2b5-c719-ba79-c0db4a11f482@embeddedor.com>
Date:   Thu, 27 Feb 2020 13:33:46 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Russell King <linux@...linux.org.uk>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] amba: tegra-ahb: Replace zero-length array with
 flexible-array member

Hi all,

Friendly ping: Who can take this?

Thanks
--
Gustavo

On 2/11/20 15:02, 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
> inadvertenly introduced[3] to the codebase from now on.
> 
> [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@...eddedor.com>
> ---
>  drivers/amba/tegra-ahb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/amba/tegra-ahb.c b/drivers/amba/tegra-ahb.c
> index b0b688c481e8..e9e5c7bb580c 100644
> --- a/drivers/amba/tegra-ahb.c
> +++ b/drivers/amba/tegra-ahb.c
> @@ -129,7 +129,7 @@ static const u32 tegra_ahb_gizmo[] = {
>  struct tegra_ahb {
>  	void __iomem	*regs;
>  	struct device	*dev;
> -	u32		ctx[0];
> +	u32		ctx[];
>  };
>  
>  static inline u32 gizmo_readl(struct tegra_ahb *ahb, u32 offset)
>