Messages in this thread | | | Date | Wed, 04 Sep 2013 10:20:50 -0700 | From | Randy Dunlap <> | Subject | Re: do_div() silently truncates "base" to 32bit |
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On 09/04/13 08:32, Anatol Pomozov wrote: > Hi > > On Fri, Aug 30, 2013 at 5:50 PM, Anatol Pomozov > <anatol.pomozov@gmail.com> wrote: >> Hi, Joe >> >> On Fri, Aug 30, 2013 at 4:28 PM, Joe Perches <joe@perches.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. > > I looked at the places where do_div() passes incorrect parameters and > it is quite a lot of them. It would be better to warn users until all > the places are fixed. Is there any BUILD_WARN_ON() macro? >
Not that I know of or can find.
-- ~Randy
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