`fetestexcept`

Article
10/26/2022

Determines which of the specified floating-point exception status flags are currently set.

Syntax

int fetestexcept(
   int excepts
);

Parameters

excepts
A bitwise OR of the floating-point status flags to test.

Return value

On success, returns a bitmask containing a bitwise OR of the floating-point exception macros that correspond to the exception status flags currently set. Returns 0 if none of the exceptions are set.

Remarks

Use the fetestexcept function to determine which exceptions were raised by a floating point operation. Use the excepts parameter to specify which exception status flags to test. The fetestexcept function uses these exception macros defined in <fenv.h> in excepts and the return value:

Exception Macro	Description
`FE_DIVBYZERO`	A singularity or pole error occurred in an earlier floating-point operation; an infinity value was created.
`FE_INEXACT`	The function was forced to round the stored result of an earlier floating-point operation.
`FE_INVALID`	A domain error occurred in an earlier floating-point operation.
`FE_OVERFLOW`	A range error occurred; an earlier floating-point operation result was too large to be represented.
`FE_UNDERFLOW`	An earlier floating-point operation result was too small to be represented at full precision; a denormal value was created.
`FE_ALL_EXCEPT`	The bitwise OR of all supported floating-point exceptions.

The specified excepts argument may be 0, one of the supported floating-point exception macros, or the bitwise OR of two or more of the macros. The effect of any other excepts argument value is undefined.

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
`fetestexcept`	<fenv.h>	<cfenv>

For more compatibility information, see Compatibility.