C - <fenv.h>
The C <fenv.h> header file declares a set of functions and macros to work with the floating-point environment. The floating-point environment is the set of floating-point status flags and control modes. Specific about the contents of the floating-point environment depend on the implementation, but the status flags generally include the floating-point exceptions and their associated information, and the control modes include at least the rounding direction.
Note: The library <fenv.h> was a part of extension, adopted by ANSI in 2000, commonly referred to as C99.
Library Functions
Floating-point Exceptions
| Functions | Description |
|---|---|
| feclearexcept() | Clears floating-point exceptions. |
| feraiseexcept() | Raises floating-point exceptions. |
| fegetexceptflag() | Gets floating-point exceptions. |
| fesetexceptflag() | Sets floating-point exceptions. |
Rounding direction
| Functions | Description |
|---|---|
| fegetround() | Get rounding direction mode. |
| fesetround() | Set rounding direction mode. |
Entire environment
| Functions | Description |
|---|---|
| fegetenv() | Gets floating-point environment. |
| fesetenv() | Sets floating-point environment. |
| feholdexcept() | Holds floating-point exceptions. |
| feupdateenv() | Updates floating-point environment. |
Others
| Functions | Description |
|---|---|
| fetestexcept() | Test for floating-point exceptions. |
Library Macros
Floating-point Exceptions
| Macros | Description |
|---|---|
| FE_DIVBYZERO | Pole error exception |
| FE_INEXACT | Inexact result exception |
| FE_INVALID | Invalid argument exception |
| FE_OVERFLOW | Overflow range error exception |
| FE_UNDERFLOW | Underflow range error exception |
| FE_ALL_EXCEPT | All exceptions |
Rounding directions
| Macros | Description |
|---|---|
| FE_DOWNWARD | Rounding towards negative infinity. |
| FE_TONEAREST | Rounding towards nearest representable value. |
| FE_TOWARDZERO | Rounding towards zero. |
| FE_UPWARD | Rounding towards positive infinity. |
Entire environment
| Macros | Description |
|---|---|
| FE_DFL_ENV | Default environment. |
Library Pragmas
| Pragmas | Description |
|---|---|
| FENV_ACCESS | Access to Floating-point environment. |
