STDC_COUNT_ZEROS(3)    FreeBSD Library Functions Manual    STDC_COUNT_ZEROS(3)

NAME

     stdc_count_zeros - count the zeros in an integer

SYNOPSIS

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

     unsigned int
     stdc_count_zeros_uc(unsigned char value);

     unsigned int
     stdc_count_zeros_us(unsigned short value);

     unsigned int
     stdc_count_zeros_ui(unsigned int value);

     unsigned int
     stdc_count_zeros_ul(unsigned long value);

     unsigned int
     stdc_count_zeros_ull(unsigned long long value);

     unsigned int
     stdc_count_zeros(value);

DESCRIPTION

     The stdc_count_zeros_type() family of functions returns the number of
     bits set to 0 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.  This is also known as the
     "population count" (popcount) or "Hamming weight" of the complement of
     value.  The stdc_count_zeros(value) type-generic macro picks the
     appropriate stdc_count_zeros_type() function based on the type of value.

RETURN VALUES

     Returns the number of bits set to 0 in value.

SEE ALSO

     stdbit(3), stdc_count_ones(3)

STANDARDS

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

HISTORY

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

AUTHOR

     Robert Clausecker <fuz@FreeBSD.org>

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