_fpieee_flt

Article
04/22/2008

Invokes a user-defined trap handler for IEEE floating-point exceptions.

int _fpieee_flt( 
   unsigned long excCode,
   struct _EXCEPTION_POINTERS *excInfo,
   int handler(_FPIEEE_RECORD *) 
);

Parameters

excCode
Exception code.
excInfo
Pointer to the Windows NT exception information structure.
handler
Pointer to the user's IEEE trap-handler routine.

Return Value

The return value of _fpieee_flt is the value returned by handler. As such, the IEEE filter routine might be used in the except clause of a structured exception-handling (SEH) mechanism.

Remarks

The _fpieee_flt function invokes a user-defined trap handler for IEEE floating-point exceptions and provides it with all relevant information. This routine serves as an exception filter in the SEH mechanism, which invokes your own IEEE exception handler when necessary.

The _FPIEEE_RECORD structure, defined in Fpieee.h, contains information pertaining to an IEEE floating-point exception. This structure is passed to the user-defined trap handler by _fpieee_flt.

_FPIEEE_RECORD field	Description
unsigned int RoundingMode, unsigned int Precision	These fields contain information about the floating-point environment at the time the exception occurred.
unsigned int Operation	Indicates the type of operation that caused the trap. If the type is a comparison (_FpCodeCompare), you can supply one of the special _FPIEEE_COMPARE_RESULT values (as defined in Fpieee.h) in the Result.Value field. The conversion type (_FpCodeConvert) indicates that the trap occurred during a floating-point conversion operation. You can look at the Operand1 and Result types to determine the type of conversion being attempted.
_FPIEEE_VALUE Operand1, _FPIEEE_VALUE Operand2, _FPIEEE_VALUE Operand3, _FPIEEE_VALUE Result	These structures indicate the types and values of the proposed result and operands: OperandValid Flag indicating whether the responding value is valid. Format Data type of the corresponding value. The format type might be returned even if the corresponding value is not valid. Value Result or operand data value. Note: Operand3 is only used with Itanium Processor Family (IPF) functions.
_FPIEEE_EXCEPTION_FLAGS Cause, _FPIEEE_EXCEPTION_FLAGS Enable, _FPIEEE_EXCEPTION_FLAGS Status	_FPIEEE_EXCEPTION_FLAGS contains one bit field per type of floating point exception. There is a correspondence between these fields and the arguments used to mask the exceptions supplied to _controlfp. The exact meaning of each bit depends on context: Cause Each set bit indicates the particular exception that was raised. Enable Each set bit indicates that the particular exception is currently unmasked. Status Each set bit indicates that the particular exception is currently pending. This includes exceptions that have not been raised because they were masked by _controlfp.

Pending exceptions that are disabled are raised when you enable them. This can result in undefined behavior when using _fpieee_flt as an exception filter. Always call _clearfp before enabling floating point exceptions.

Requirements

Function	Required header
_fpieee_flt	<fpieee.h>

For more compatibility information, see Compatibility in the Introduction.

Example

// crt_fpieee.c
// This program demonstrates the implementation of
// a user-defined floating-point exception handler using the
// _fpieee_flt function.

#include <fpieee.h>
#include <excpt.h>
#include <float.h>
#include <stddef.h>

int fpieee_handler( _FPIEEE_RECORD * );

int fpieee_handler( _FPIEEE_RECORD *pieee )
{
   // user-defined ieee trap handler routine:
   // there is one handler for all 
   // IEEE exceptions

   // Assume the user wants all invalid 
   // operations to return 0.

   if ((pieee->Cause.InvalidOperation) && 
       (pieee->Result.Format == _FpFormatFp32)) 
   {
        pieee->Result.Value.Fp32Value = 0.0F;

        return EXCEPTION_CONTINUE_EXECUTION;
   }
   else
      return EXCEPTION_EXECUTE_HANDLER;
}

#define _EXC_MASK    \
    _EM_UNDERFLOW  + \
    _EM_OVERFLOW   + \
    _EM_ZERODIVIDE + \
    _EM_INEXACT

int main( void )
{
   // ...

   __try {
      // unmask invalid operation exception
      _controlfp_s(NULL, _EXC_MASK, _MCW_EM); 

      // code that may generate 
      // fp exceptions goes here
   }
   __except ( _fpieee_flt( GetExceptionCode(),
                GetExceptionInformation(),
                fpieee_handler ) ){

      // code that gets control 

      // if fpieee_handler returns
      // EXCEPTION_EXECUTE_HANDLER goes here

   }

   // ...
}

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

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