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Date: Sat, 04 Aug 2012 00:20:02 +0200 From: Sasha Levin <levinsasha928@...il.com> To: Tejun Heo <tj@...nel.org> CC: torvalds@...ux-foundation.org, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, paul.gortmaker@...driver.com, davem@...emloft.net, rostedt@...dmis.org, mingo@...e.hu, ebiederm@...ssion.com, aarcange@...hat.com, ericvh@...il.com, netdev@...r.kernel.org Subject: Re: [RFC v2 1/7] hashtable: introduce a small and naive hashtable On 08/03/2012 11:48 PM, Tejun Heo wrote: > Hello, > > On Fri, Aug 03, 2012 at 11:41:34PM +0200, Sasha Levin wrote: >> I forgot to comment on that one, sorry. >> >> If we put hash entries after struct hash_table we don't take the >> bits field size into account, or did I miss something? > > So, if you do the following, > > struct { > struct { > int i; > long ar[]; > } B; > long __ar_storage[32]; > } A; struct A should have been an union, right? > It should always be safe to dereference A.B.ar[31]. I'm not sure > whether this is something guaranteed by C tho. Maybe compilers are > allowed to put members in reverse order but I think we already depend > on the above. why is accessing A.B.ar[31] safe? __ar_storage is only 32*sizeof(long) bytes long, while struct B would need to be 32*sizeof(long) + sizeof(int) bytes long so that A.B.ar[31] access would be safe. > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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