### 28.5 Floating Arithmetic Exception Flags ¶

Sticky exception flags record the occurrence of particular conditions: once set, they remain set until the program explicitly clears them.

The conditions include invalid operand, division by zero, inexact result (i.e., one that required rounding), underflow, and overflow. Some extended floating-point designs offer several additional exception flags. The functions `feclearexcept`, `feraiseexcept`, `fetestexcept`, `fegetexceptflags`, and `fesetexceptflags` provide a standardized interface to those flags. See Status bit operations in The GNU C Library Reference Manual.

One important use of those flags is to do a computation that is normally expected to be exact in floating-point arithmetic, but occasionally might not be, in which case, corrective action is needed. You can clear the inexact result flag with a call to `feclearexcept (FE_INEXACT)`, do the computation, and then test the flag with `fetestexcept (FE_INEXACT)`; the result of that call is 0 if the flag is not set (there was no rounding), and 1 when there was rounding (which, we presume, implies the program has to correct for that).