phoenix-rtos-doc / libc / functions / l / log10.part-impl.md

log10

Synopsis

#include <math.h>

double log10(double x);

float log10f(float x);

long double log10l(long double x);

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

These functions shall compute the base 10 logarithms of their argument x, log10(x).

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Return value

Upon successful completion, these functions shall return the base 10 logarithms of x.

If x is ±0, a pole error shall occur and log10(), log10f(), and log10l() shall return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

For finite values of x that are less than 0, or if x is -Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.

If x is NaN, a NaN shall be returned.
If x is 1, +0 shall be returned.
If x is +Inf, +Inf shall be returned.

Errors

These functions shall fail if:

Domain Error - The finite value of x is negative, or x is -Inf. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to EDOM. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.
Pole Error - The value of x is zero. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to ERANGE. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.

Tests

Untested

Known bugs

None