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powerof2(3) Library Functions Manual powerof2(3)
powerof2 - test if a value is a power of 2
Standard C library (libc)
#include <sys/param.h> int powerof2(x);
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.
True or false, if x is a power of 2 or not, respectively.
BSD.
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.
stdc_bit_ceil(3), stdc_bit_floor(3)
Linux man-pages (unreleased) (date) powerof2(3)