feholdexcept

[アーティクル]
06/05/2017

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The latest version of this topic can be found at feholdexcept2.

Saves the current floating-point environment in the specified object, clears the floating-point status flags, and, if possible, puts the floating-point environment into non-stop mode.

Syntax

int feholdexcept(  
   fenv_t *penv  
);

Parameters

penv
Pointer to an fenv_t object to contain a copy of the floating-point environment.

Return Value

Returns zero if and only if the function is able to successfully turn on non-stop floating-point exception handling.

Remarks

The feholdexcept function is used to store the state of the current floating point environment in the fenv_t object pointed to by penv, and to set the environment to not interrupt execution on floating-point exceptions. This is known as non-stop mode. This mode continues until the environment is restored using fesetenv or feupdateenv.

You can use this function at the beginning of a subroutine that needs to hide one or more floating-point exceptions from the caller. To report an exception, you can simply clear the unwanted exceptions by using feclearexcept, and then end the non-stop mode with a call to feupdateenv.

To use this function, you must turn off floating-point optimizations that could prevent access by using the #pragma fenv_access(on) directive prior to the call. For more information, see fenv_access.

Requirements

Function	C header	C++ header
`feholdexcept`	<fenv.h>	<cfenv>

For additional compatibility information, see Compatibility.

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