Re: [PATCH (updated)] Avoid annoying build warning on 32-bitplatforms

[Martin Zwickel]

On Wed, 20 Oct 2004 03:23:43 -0700
Chris Wedgwood <cw@xxxxxxxx> bubbled:

> On Wed, Oct 20, 2004 at 11:56:45AM +0200, Mikael Pettersson wrote:
> 
> > There's a coding idiom for doing this: just break up
> > the ">> 32" in two steps, like: ((time >> 31) >> 1).
> 
> i assumed gcc would complain there too but it doesn't and it does
> optimize this away (i checked)
> 
> > Definitely preferable over #ifdef:s.
> 
> indeed
> 
> 
> 
> Avoid annoying gcc warning on 32-bit platforms.
> 
> Signed-off-by: cw@xxxxxxxx
> 
> ===== drivers/char/random.c 1.57 vs edited =====
> --- 1.57/drivers/char/random.c	2004-10-05 14:21:53 -07:00
> +++ edited/drivers/char/random.c	2004-10-20 03:19:17 -07:00
> @@ -818,12 +818,10 @@ static void add_timer_randomness(struct 
>  	 * jiffies.
>  	 */
>  	time = get_cycles();
> -	if (time != 0) {
> -		if (sizeof(time) > 4)
> -			num ^= (u32)(time >> 32);
> -	} else {
> +	if (time)
> +		num ^= (u32)((time >> 32) >> 1);
                                      ^^ errr ... should be 31 ?!?!
> +	else
>  		time = jiffies;
> -	}
>  
>  	/*
>  	 * Calculate number of bits of randomness we probably added.
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/


-- 
MyExcuse:
We've run out of licenses

Martin Zwickel <martin.zwickel@xxxxxxxxxxxxxx>
Research & Development

TechnoTrend AG <http://www.technotrend.de>

Attachment: pgp00000.pgp
Description: PGP signature