Inexact result exception
This macro expands to a value of type int that identifies the floating-point exception raised on inexact results.

Inexact exceptions are raised to signal when the return type of an operation cannot represent the result with exact accuracy (such as 1.0/3.0 or sqrt(2.0) on most implementations), or when a function cannot produce an exact result for some other reason.

It is defined as a value that is an exact power of two, allowing several floating-point exceptions to be combined (using the bitwise OR operator: |) into a single value:
macro valuedescription
FE_DIVBYZEROPole error: division by zero, or some other asymptotically infinite result (from finite arguments).
FE_INEXACTInexact: the result is not exact.
FE_INVALIDDomain error: At least one of the arguments is a value for which the function is not defined.
FE_OVERFLOWOverflow range error: The result is too large in magnitude to be represented as a value of the return type.
FE_UNDERFLOWUnderflow range error: The result is too small in magnitude to be represented as a value of the return type.
FE_ALL_EXCEPTAll exceptions (selects all of the exceptions supported by the implementation).
Certain library implementations may support additional floating-point exception values (with their corresponding macros also beginning with FE_).
Libraries may define in <fenv.h> only the macro values above they support (the others may not be defined).
At least all of the above macro values are defined in <cfenv> (even if not supported by the implementation).

See also