Floating-point environment
The floating-point environment is the set of floating-point status flags and control modes supported by the implementation. It is thread-local, each thread inherits the initial state of its floating-point environment from the parent thread. Floating-point operations modify the floating-point status flags to indicate abnormal results or auxiliary information. The state of floating-point control modes affects the outcomes of some floating-point operations.
The floating-point environment access and modification is only meaningful when
#pragma STDC FENV_ACCESS is set to ON. Otherwise the implementation is free to assume that floating-point control modes are always the default ones and that floating-point status flags are never tested or modified. In practice, few current compilers, such as HP aCC, Oracle Studio, and IBM XL, support the #pragma explicitly, but most compilers allow meaningful access to the floating-point environment anyway.
Types
| Defined in header
<fenv.h> | |
| fenv_t | The type representing the entire floating-point environment |
| fexcept_t | The type representing all floating-point status flags collectively |
Functions
| (C99) |
clears the specified floating-point status flags (function) |
| (C99) |
determines which of the specified floating-point status flags are set (function) |
| (C99) |
raises the specified floating-point exceptions (function) |
| (C99)(C99) |
copies the state of the specified floating-point status flags from or to the floating-point environment (function) |
| (C99)(C99) |
gets or sets rounding direction (function) |
| (C99) |
saves or restores the current floating point environment (function) |
| (C99) |
saves the environment, clears all status flags and ignores all future errors (function) |
| (C99) |
restores the floating-point environment and raises the previously raise exceptions (function) |
Macros
| floating-point exceptions (macro constant) | |
| floating-point rounding direction (macro constant) | |
| (C99) |
default floating-point environment (macro constant) |
References
- C11 standard (ISO/IEC 9899:2011):
- 7.6 Floating-point environment <fenv.h> (p: 206-215)
- 7.31.4 Floating-point environment <fenv.h> (p: 455)
- C99 standard (ISO/IEC 9899:1999):
- 7.6 Floating-point environment <fenv.h> (p: 187-196)