Re: Is __ffs64 supposed to be zero based?
From: Clemens Ladisch
Date: Wed Nov 06 2013 - 06:52:54 EST
Ben Greear wrote:
> Similarly named methods elsewhere seem to indicate it is supposed to be
> ones-based counting (ie, bit (1<<0) would be considred 'bit 1'.
ffs() is defined to use one-based counting:
__ffs() uses zero-based counting. On gcc, it's likely to be implemented
with__builtin_ctz*(), whose documentation says:
| Returns the number of trailing 0-bits in x, starting at the least
| significant bit position.
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