linux-kernel - Re: [PATCH] kdb: kdb_main: mark expected switch fall-throughs

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Message-ID: <a47008fd-1e52-a268-8085-a2cdcd5dce01@linaro.org>
Date:   Wed, 15 Aug 2018 15:34:06 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Jason Wessel <jason.wessel@...driver.com>
Cc:     kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kdb: kdb_main: mark expected switch fall-throughs

On 05/08/18 05:14, Gustavo A. R. Silva wrote:
> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> where we are expecting to fall through.
> 
> Addresses-Coverity-ID: 115090 ("Missing break in switch")
> Addresses-Coverity-ID: 115091 ("Missing break in switch")
> Addresses-Coverity-ID: 114700 ("Missing break in switch")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Adding fall through isn't wrong but its reasonable to ask why there is a 
complex hand unrolled loop here in the first place (and doubly so 
without a comment). The whole switch statement would be much clear 
expressed as:

	for (j=0; j<bytesperword; j++)
		*c++ = printable_char(*cp++);
	addr += bytesperword;


Daniel.


> ---
>   kernel/debug/kdb/kdb_main.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 2ddfce8..2249645 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -1545,13 +1545,16 @@ static void kdb_md_line(const char *fmtstr, unsigned long addr,
>   				*c++ = printable_char(*cp++);
>   				*c++ = printable_char(*cp++);
>   				addr += 4;
> +				/* fall through */
>   			case 4:
>   				*c++ = printable_char(*cp++);
>   				*c++ = printable_char(*cp++);
>   				addr += 2;
> +				/* fall through */
>   			case 2:
>   				*c++ = printable_char(*cp++);
>   				addr++;
> +				/* fall through */
>   			case 1:
>   				*c++ = printable_char(*cp++);
>   				addr++;
>