ilogb(), ilogbf(), ilogbl()

Compute the integral part of a logarithm

Synopsis:

#include <math.h>

int ilogb( double x );

int ilogbf( float x );

int ilogbl( long double x );

x: The number for which you want to compute the integral part of the logarithm.

libm: The general-purpose math library.
libm-sve: (QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

If you want only selected processes to run with the SVE version, you can include both libraries in your OS image and use the -l m or -l m-sve option to qcc to link explicitly against the appropriate one.
If you want all processes to use the SVE version, include libm-sve.so in your OS image and set up a symbolic link from libm.so to libm-sve.so. Use the -l m option to qcc to link against the library.

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.

The ilogb(), ilogbf(), and ilogbl() functions compute the integral part of:

log_r |x|

as a signed integral value, for nonzero finite x, where r is the radix of the machine's floating point arithmetic.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

Call feclearexcept(FE_ALL_EXCEPT) before calling ilogb(), ilogbf(), or ilogbl().
On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

The exponent part of x, in integer format.

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.