Messages in this thread | | | Date | Thu, 6 Nov 2014 10:56:57 +0100 | From | Maxime Coquelin <> | Subject | Re: [PATCH v3] bitops: Fix shift overflow in GENMASK macros |
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On 11/05/2014 05:44 PM, Peter Zijlstra wrote: > On Wed, Nov 05, 2014 at 04:47:14PM +0100, Maxime Coquelin wrote: >> On 11/05/2014 12:10 PM, Rasmus Villemoes wrote: >>> On Tue, Nov 04 2014, Maxime COQUELIN <maxime.coquelin@st.com> 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)) >>> Slightly bikeshedding here, but may I suggest spelling it >>> >>> (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h)))) >>> >>> ? This will ensure the arguments are expanded once each, and will, IMHO, >>> DTRT if/when l > h (namely, yield 0). >> That's a good point. >> >> Peter, what is your view? > I'm fine with that, feel free to post another version and I'll replace > v3.
Thanks Peter, v4 just sent.
Regards, Maxime
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