powerof2(3) Library Functions Manual powerof2(3)
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 nega-
tive values can invoke undefined behavior. For example, the following
invokes undefined behavior: powerof2(INT_MIN);. Call it only with un-
signed types to be safe.
SEE ALSO
stdc_bit_ceil(3), stdc_bit_floor(3)
Linux man-pages 6.03 2022-12-31 powerof2(3)
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