Messages in this thread | | | Date | Wed, 4 Sep 2013 08:32:37 -0700 | Subject | Re: do_div() silently truncates "base" to 32bit | From | Anatol Pomozov <> |
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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?
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