# IEEE_HANDLER

Portability Function: Establishes a handler for IEEE exceptions.

## Module

USE IFPORT

result = IEEE_HANDLER (action, exception, handler)

action | (Input) Character*(*). One of the following literal IEEE actions: 'GET', 'SET', or 'CLEAR'. For more details on these actions, see IEEE_FLAGS.
exception | (Input) Character*(*). One of the following literal IEEE exception flags: 'inexact', 'underflow', 'overflow', 'division', 'invalid', 'all' (which equals the previous five flags), or 'common' (which equals 'invalid', 'overflow', 'underflow', and 'division'). The flags 'all' or 'common' should only be used for actions SET or CLEAR.
handler | (Input) The address of an external signal-handling routine.

## Results

The result type is INTEGER(4) on IA-32 architecture; INTEGER(8) on Intel® 64 architecture. The result is 0 if successful; otherwise, 1.

IEEE_HANDLER calls a signal-handling routine to establish a handler for IEEE exceptions. It also enables an FPU trap corresponding to the required exception.

The state of the FPU is not defined in the handler routine. When the FPU trap occurs, the program invokes the handler routine. After the handler routine is executed, the program terminates.

The handler routine gets the exception code in the SIGINFO argument. SIGNO is the number of the system signal. The meaning of the SIGINFO constants appear in the following table (defined in the IFPORT module):

FPE$INVALID | Invalid operation
FPE$ZERODIVIDE | Divide-by-zero
FPE$OVERFLOW | Numeric overflow
FPE$UNDERFLOW | Numeric underflow
FPE$INEXACT | Inexact result (precision)

'GET' actions return the location of the current handler routine for exception cast to an INTEGER.

## Example

The following example creates a handler routine and sets it to trap divide-by-zero:

    PROGRAM TEST_IEEE
     REAL :: X, Y, Z
     CALL FPE_SETUP
     X = 0.
     Y = 1.
     Z = Y / X
    END PROGRAM
    SUBROUTINE FPE_SETUP
    USE IFPORT
    IMPLICIT NONE
     INTERFACE
       SUBROUTINE FPE_HANDLER(SIGNO, SIGINFO)
         INTEGER(4), INTENT(IN) :: SIGNO, SIGINFO
       END SUBROUTINE
     END INTERFACE
     INTEGER IR
     IR = IEEE_HANDLER('set','division',FPE_HANDLER)
    END SUBROUTINE FPE_SETUP
    SUBROUTINE FPE_HANDLER(SIG, CODE)
     USE IFPORT
     IMPLICIT NONE
     INTEGER SIG, CODE
     IF(CODE.EQ.FPE$ZERODIVIDE) PRINT *,'Occurred divide by zero.'
     CALL ABORT
    END SUBROUTINE FPE_HANDLER

Parent topic: H to I

## See Also

IEEE_FLAGS