C Standard Library

C <fenv.h> - FE_INVALID

The FE_INVALID macro expands to a value of type integer constant expression that is distinct powers of 2, which uniquely identifies the floating-point exception raised on invalid arguments.

Invalid argument exceptions are raised when the argument passed to a function is out of its domain (function is not defined for that value), for example - sqrt(-1.0). The value returned by a function that raises this exception is unspecified.

Definition in the <fenv.h> header file is:

#define FE_INVALID  /*implementation defined power of 2*/

The details about all floating-point exception macros are listed below:

Macros	Description
FE_DIVBYZERO	Pole error exception occurred in an earlier floating-point operation.
FE_INEXACT	Inexact result exception occurred in an earlier floating-point operation (rounding was necessary to store the result).
FE_INVALID	Invalid argument exception occurred (domain error occurred) in an earlier floating-point operation.
FE_OVERFLOW	Overflow range error exception occurred in an earlier floating-point operation (result was too large to be representable).
FE_UNDERFLOW	Underflow range error exception occurred in an earlier floating-point operation (result was subnormal with a loss of precision).
FE_ALL_EXCEPT	Bitwise OR of all supported floating-point exceptions.

Certain library implementations may define additional macro constants in <fenv.h> to identify additional floating-point exceptions (with their corresponding macros also beginning with FE_).

See math_errhandling for more details.

Example:

The example below shows the usage of FE_INVALID macro.

#include <stdio.h>
#include <fenv.h>
#include <math.h>
 
int main (){
  printf("sqrt(-1.0) = %f\n", sqrt(-1));
  if(fetestexcept(FE_INVALID))
    printf("Domain error is reported.\n");
  else
    printf("Domain error is not reported.\n");

  return 0;
}

The output of the above code will be:

sqrt(-1.0) = -nan
Domain error is reported.

❮ C <fenv.h> Library