linux-kernel - Re: [PATCH] xen, fbfront: mark expected switch fall-through

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Message-ID: <f8ff03de-9d7c-233a-cd86-37269667db0c@gmail.com>
Date:   Thu, 28 Feb 2019 13:51:53 +0200
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:     Kees Cook <keescook@...omium.org>, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        xen-devel <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH] xen, fbfront: mark expected switch fall-through

+Xen-devel list

On 2/27/19 10:53 PM, Gustavo A. R. Silva wrote:
> In preparation to enabling -Wimplicit-fallthrough, mark switch
> cases where we are expecting to fall through.
>
> This patch fixes the following warning:
>
> drivers/video/fbdev/xen-fbfront.c: In function ‘xenfb_backend_changed’:
> drivers/video/fbdev/xen-fbfront.c:678:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>     if (dev->state == XenbusStateClosed)
>        ^
> drivers/video/fbdev/xen-fbfront.c:681:2: note: here
>    case XenbusStateClosing:
>    ^~~~
>
> Warning level 3 was used: -Wimplicit-fallthrough=3
>
> Notice that, in this particular case, the code comment is modified
> in accordance with what GCC is expecting to find.
>
> This patch is part of the ongoing efforts to enable
> -Wimplicit-fallthrough.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>   drivers/video/fbdev/xen-fbfront.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c
> index 6a4bbc9e1fb0..a3d6b6db221b 100644
> --- a/drivers/video/fbdev/xen-fbfront.c
> +++ b/drivers/video/fbdev/xen-fbfront.c
> @@ -677,7 +677,7 @@ static void xenfb_backend_changed(struct xenbus_device *dev,
>   	case XenbusStateClosed:
>   		if (dev->state == XenbusStateClosed)
>   			break;
> -		/* Missed the backend's CLOSING state -- fallthrough */
> +		/* fall through - Missed the backend's CLOSING state. */
>   	case XenbusStateClosing:
>   		xenbus_frontend_closed(dev);
>   		break;