IEEE_HANDLER

 

Portability Function: Establishes a handler for IEEE exceptions.

Module

USE IFPORT

Syntax

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 IntelĀ® 64 architecture and IA-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

See Also