Messages in this thread | | | Date | Thu, 28 Aug 2008 22:59:59 +0200 | From | "Vegard Nossum" <> | Subject | Re: [RFC][PATCH] bitfields API |
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On Thu, Aug 28, 2008 at 10:27 PM, Adrian Bunk <bunk@kernel.org> wrote: > On Thu, Aug 28, 2008 at 09:40:47PM +0300, Pekka Enberg wrote: >> Hi Alexey, >> >> Alexey Dobriyan wrote: >>> On Thu, Aug 28, 2008 at 08:32:23PM +0200, Vegard Nossum wrote: >>>> How do you feel about this patch? It's all about making kmemcheck more >>>> useful... and not much else. Does it have any chance of entering the >>>> kernel along with kmemcheck (when/if that happens)? >>> >>> DEFINE_BITFIELD is horrible. >> >> Heh, heh, one alternative is to have a kmemcheck_memset() thingy that >> unconditionally zeroes bit fields and maybe is a no-op when kmemcheck is >> disabled. > > This sounds as if this might cause bugs to disappear when debugging gets > turned on? > > Or do I miss anything?
You are correct :-)
Almost all the possible solutions (at least the feasible ones) are trade-offs between false-positives and false-negatives.
So here we are trading a bunch of false-positive errors (a couple of thousand for transferring a 1M file over ssh :-)) for detecting any code that uses an uninitialized flag in struct skbuff. So in this case it is more useful to hide reports about this single bit-field.
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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