# fmath-errno

Tells the compiler that errno can be reliably tested after calls to standard math library functions.

## Syntax

Linux: | -fmath-errno -fno-math-errno

macOS: | -fmath-errno -fno-math-errno

Windows: | None

## Arguments

None

## Default

-fno-math-errno | The compiler assumes that the program does not test errno after calls to standard math library functions.

## Description

This option tells the compiler to assume that the program tests errno after calls to math library functions. This restricts optimization because it causes the compiler to treat most math functions as having side effects.

Option -fno-math-errno tells the compiler to assume that the program does not test errno after calls to math library functions. This frequently allows the compiler to generate faster code. Floating-point code that relies on IEEE exceptions instead of errno to detect errors can safely use this option to improve performance.

## IDE Equivalent

None

## Alternate Options

None

Parent topic: Data Options