Messages in this thread | | | Date | Tue, 13 May 2008 18:46:46 +0400 | From | Nickolay Vinogradov <> | Subject | Re: [PATCH] asm-generic/bitops/fls64.h |
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Alexander van Heukelum пишет:
>> No. "fls" is for finding the last set bit in an _int_. It is not >> supposed to have random crap passed to it, such as types longer than >> sizeof(int). >> >> If you're going to pass long long (64-bit) arguments to fls, and then >> cast them to a u32, you're truncating the value, and you'll get the >> wrong answer if bit 33 or greater is set. If you don't actually care >> about the upper bits, don't pass a 64-bit quantity to fls(). >> >> If you want to use fls with a long long, use fls64 instead. Or for top >> marks, use a u64 and fls64. > > But that was the problem we began with: the generic fls64 passes an u64 > to fls. Nickolay's original patch solves that by putting a cast to u32 > in fls64. I did not, however, understand why the cast was needed.
The cast was needed because fls is a macro, not a function.
-- Nickolay Vinogradov Protei Research and Development Center St.Petersburg, 194044, Russia Tel.: +7 812 449 47 27 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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