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)
See also
C++ documentation for Floating-point environment |
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