linux-kernel - Re: [PATCH]kconfig:mconf: avoid unneeded memcpy

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Message-ID: <20131006151821.GA3346@udknight>
Date:	Sun, 6 Oct 2013 23:18:21 +0800
From:	Wang YanQing <udknight@...il.com>
To:	mmarek@...e.cz, linux-kbuild@...r.kernel.org,
	yann.morin.1998@...e.fr, bpoirier@...e.de, walch.martin@....de,
	jdelvare@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]kconfig:mconf: avoid unneeded memcpy

On Sun, Oct 06, 2013 at 01:57:15AM +0800, Wang YanQing wrote:
> In function update_text we assign jump key label
> per page (1)-(9) cycled, and use three space char
> as the header after k exceed JUMP_NB.
> 
> We don't need to call memcpy with header of three
> space char, because it changes nothing, it just
> copy what was there.
> 
> I don't think we need to clear old jump key label in
> current implementation, I can't image out any case
> which a search result could change its jump key label,
> unless user search new string, but then we will re-assign
> jump key label, and it will be fix after that.
> 
> Signed-off-by: Wang YanQing <udknight@...il.com>
> ---
>  scripts/kconfig/mconf.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/scripts/kconfig/mconf.c b/scripts/kconfig/mconf.c
> index 2c39631..ff9d737 100644
> --- a/scripts/kconfig/mconf.c
> +++ b/scripts/kconfig/mconf.c
> @@ -379,11 +379,8 @@ static void update_text(char *buf, size_t start, size_t end, void *_data)
>  				data->keys[k] = key;
>  				data->targets[k] = pos->target;
>  				k++;
> -			} else {
> -				sprintf(header, "   ");
> +				memcpy(buf + pos->offset, header, sizeof(header) - 1);
>  			}
> -
> -			memcpy(buf + pos->offset, header, sizeof(header) - 1);
>  		}
>  	}
>  	data->keys[k] = 0;
> -- 
> 1.7.12.4.dirty

Hi all, please ignore this patch.

I image out that we need to clear old jump label when we run 
make menuconfig in a x11 terminal with high resolution that
could show more than 9 item in one page.

Sorry.
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