linux-kernel - Re: do_div() silently truncates "base" to 32bit

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Message-ID: <CAOMFOmVrNu2ZDrBrm7Rt_p-C3Po0d6HmyCQ2HvJSVT=cx+OjOw@mail.gmail.com>
Date:	Fri, 30 Aug 2013 17:50:14 -0700
From:	Anatol Pomozov <anatol.pomozov@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Randy Dunlap <rdunlap@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
	bernie@...eler.com, Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: do_div() silently truncates "base" to 32bit

Hi, Joe

On Fri, Aug 30, 2013 at 4:28 PM, Joe Perches <joe@...ches.com> wrote:
> On Fri, 2013-08-30 at 15:48 -0700, Randy Dunlap wrote:
>> On 08/30/13 15:14, Anatol Pomozov wrote:
>> > But another question still remains: why compiler does not warn that
>> > size truncation happens? How to prevent bugs like CFQ one in the
>> > future? Should we add a compile-time assert to do_div() to prevent
>> > passing 64 numbers in "base" macro parameter?
>> That sounds like a fine idea to me.
>
> Geert thought so too and submitted a patch
>
> http://www.spinics.net/lists/linux-btrfs/msg26788.html

Thanks it works!

block/cfq-iosched.c: In function 'cfqg_prfill_avg_queue_size':
block/cfq-iosched.c:4423:3: error: size of unnamed array is negative
make[2]: *** [block/gfq-iosched.s] Error 1
make[1]: *** [block/gfq-iosched.s] Error 2



I see a number of other truncation errors. We need to fix them as well.
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