STDC_TRAILING_ONES(3)  FreeBSD Library Functions Manual  STDC_TRAILING_ONES(3)

NAME

     stdc_trailing_ones - find the number of trailing ones in an integer

SYNOPSIS

     /* -lc */
     #include <stdbit.h>

     unsigned int
     stdc_trailing_ones_uc(unsigned char value);

     unsigned int
     stdc_trailing_ones_us(unsigned short value);

     unsigned int
     stdc_trailing_ones_ui(unsigned int value);

     unsigned int
     stdc_trailing_ones_ul(unsigned long value);

     unsigned int
     stdc_trailing_ones_ull(unsigned long long value);

     unsigned int
     stdc_trailing_ones(value);

DESCRIPTION

     The stdc_trailing_ones_type() family of functions returns the number of
     trailing ones in value, where value is of type unsigned char, unsigned
     short, unsigned int, unsigned long, or unsigned long long for type being
     uc, us, ui, ul, or ull respectively.  The stdc_trailing_ones(value) type-
     generic macro picks the appropriate stdc_trailing_ones_type() function
     based on the type of value.

RETURN VALUES

     Returns the number of trailing ones in value.  If value is all ones, the
     total number of bits in the type of value is returned.

SEE ALSO

     stdbit(3), stdc_leading_ones(3), stdc_trailing_zeros(3),
     stdc_first_trailing_zero(3)

STANDARDS

     The stdc_trailing_ones_type() family of functions and the
     stdc_trailing_ones() type-generic macro conform to ISO/IEC 9899:2024
     ("ISO C23").

HISTORY

     The stdc_trailing_ones_type() family of functions and the
     stdc_trailing_ones() type-generic macro were added in FreeBSD 15.1.

AUTHOR

     Robert Clausecker <fuz@FreeBSD.org>

FreeBSD 15.1-STABLE-HBSD       November 9, 2025          STDC_TRAILING_ONES(3)