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
|
(C99)
|
floating-point exceptions (macro constant) |
|
(C99)
|
floating-point rounding direction (macro constant) |
|
(C99)
|
default floating-point environment (macro constant) |
References
- C23 standard (ISO/IEC 9899:2023):
- 7.6 Floating-point environment <fenv.h> (p: TBD)
- 7.31.4 Floating-point environment <fenv.h> (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.6 Floating-point environment <fenv.h> (p: 150-156)
- 7.31.4 Floating-point environment <fenv.h> (p: 332)
- 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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