NAME

       powerof2 - test if a value is a power of 2

LIBRARY

       Standard C library (libc)

SYNOPSIS

       #include <sys/param.h>

       int powerof2(x);

DESCRIPTION

       This macro returns true if x is a power of 2, and false otherwise.

       0  is  considered  a  power  of  2.   This can make sense considering wrapping of unsigned
       integers, and has interesting properties.

RETURN VALUE

       True or false, if x is a power of 2 or not, respectively.

STANDARDS

       This nonstandard macro is present in glibc and the BSDs.

CAVEATS

       The arguments may be evaluated more than once.

       Because this macro is implemented using  bitwise  operations,  some  negative  values  can
       invoke  undefined  behavior.   For  example,  the  following  invokes  undefined behavior:
       powerof2(INT_MIN);.  Call it only with unsigned types to be safe.

SEE ALSO

       stdc_bit_ceil(3), stdc_bit_floor(3)