From cppreference.com
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
is supported and 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, or IBM XL, support the #pragma explicitly, but most compilers allow meaningful access to the floating-point environment anyway.
Types
fenv_t
(C++11)
the type representing the entire floating-point environment
(typedef)
fexcept_t
(C++11)
the type representing all floating-point status flags collectively
(typedef)
Functions
(C++11)
clears the specified floating-point status flags
(function)
(C++11)
determines which of the specified floating-point status flags are set
(function)
(C++11)
raises the specified floating-point exceptions
(function)
fegetexceptflagfesetexceptflag
(C++11)(C++11)
copies the state of the specified floating-point status flags from or to the floating-point environment
(function)
(C++11)(C++11)
gets or sets rounding direction
(function)
(C++11)
saves or restores the current floating-point environment
(function)
(C++11)
saves the environment, clears all status flags and ignores all future errors
(function)
(C++11)
restores the floating-point environment and raises the previously raised exceptions
(function)
Macros
Notes
The floating-point exceptions are not related to the C++ exceptions. When a floating-point operation raises a floating-point exception, the status of the floating-point environment changes, which can be tested with
, but the execution of a C++ program on most implementations continues uninterrupted.
There are compiler extensions that may be used to generate C++ exceptions automatically whenever a floating-point exception is raised:
GNU libc function
enables trapping of the floating-point exceptions, which generates the signal SIGFPE. If the compiler option -fnon-call-exceptions was used, the handler for that signal may throw a user-defined C++ exception.
MSVC function
enables trapping of the floating-point exceptions, which generates a hardware exception, which can be converted to C++ exceptions with
.
See also