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Date: Tue, 4 Nov 2014 11:47:33 +0100 From: Maxime Coquelin <maxime.coquelin@...com> To: Peter Zijlstra <peterz@...radead.org> Cc: <gong.chen@...ux.intel.com>, Ingo Molnar <mingo@...nel.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, <tytso@....edu>, <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>, <kernel@...inux.com>, <eric.paire@...com> Subject: Re: [PATCH v2] bitops: Fix shift overflow in GENMASK macros On 11/04/2014 11:44 AM, Peter Zijlstra wrote: > On Tue, Nov 04, 2014 at 11:03:57AM +0100, Maxime COQUELIN wrote: > >> -#define GENMASK(h, l) (((U32_C(1) << ((h) - (l) + 1)) - 1) << (l)) >> -#define GENMASK_ULL(h, l) (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l)) >> +#define GENMASK(h, l) ((~0UL >> (BITS_PER_LONG - (h - l + 1))) << l) >> +#define GENMASK_ULL(h, l) ((~0ULL >> (BITS_PER_LONG_LONG - (h - l + 1))) << l) > OK, so you need to keep the (h) and (l) bits, macro arguments should be > wrapped in seemingly superfluous braces in order to preserve precedence > on expansion. You're right, I should have seen this.. > > My bad for not explicitly doing that when suggesting the alternative. Not a problem, v3 is coming. Maxime -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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