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The most portable way of determining if a floating-point exceptional condition has occurred is to use the floating-point exception facilities provided by C99 in {{fenv.h}} \[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\]. |
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Operating System | How to handle floating point errors | |||
|---|---|---|---|---|
Linux | Use the C99 floating-point exception functions. | |||
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="4e7d7a871dc6ad41-0d7443e1-483f4cca-b16a8a76-9fcffbd95f05182fb1d15080"><ac:plain-text-body><![CDATA[ | Windows | Either use the C99 floating-point exception function or structured exception handling through | AA. C References#MSDN]] | ]]></ac:plain-text-body></ac:structured-macro> |
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void fp_usingSEH(void) {
/* ... */
double a = 1e-40, b, c = 0.1;
float x = 0, y;
unsigned int rv ;
unmask_fpsr();
_try {
/* Store into y is inexact and underflows */
y = a;
/* divide by zero operation */
b = y / x;
/* inexact */
c = sin(30) * a;
}
_except (_fpieee_flt(
GetExceptionCode(),
GetExceptionInformation(),
fpieee_handler)) {
{
printf ("fpieee_handler: EXCEPTION_EXECUTE_HANDLER");
}
/* ... */
}
void unmask_fpsr(void) {
unsigned int u;
unsigned int control_word;
_controlfp_s(&control_word, 0, 0);
u = control_word & ~(_EM_INVALID
| _EM_DENORMAL
| _EM_ZERODIVIDE
| _EM_OVERFLOW
| _EM_UNDERFLOW
| _EM_INEXACT);
_controlfp_s( &control_word, u, _MCW_EM);
return ;
}
int fpieee_handler(_FPIEEE_RECORD *ieee) {
/* ... */
switch (ieee->RoundingMode) {
case _FpRoundNearest:
/* ... */
break;
/* Other RMs include _FpRoundMinusInfinity,
* _FpRoundPlusInfinity, _FpRoundChopped */
/* ... */
}
switch (ieee->Precision) {
case _FpPrecision24:
/* ... */
break;
/* Other Ps include _FpPrecision53*/
/* ... */
}
switch (ieee->Operation) {
case _FpCodeAdd:
/* ... */
break;
/* Other Ops include _FpCodeSubtract, _FpCodeMultiply,
* _FpCodeDivide, _FpCodeSquareRoot, _FpCodeCompare,
* _FpCodeConvert, _FpCodeConvertTrunc */
/* ... */
}
/*
* process the bitmap ieee->Cause.
* process the bitmap ieee->Enable.
* process the bitmap ieee->Status.
* process the Operand ieee->Operand1,
* evaluate format and Value.
* process the Operand ieee->Operand2,
* evaluate format and Value.
* process the Result ieee->Result,
* evaluate format and Value .
* The result should be set according to the operation
* specified in ieee->Cause and the result format as
* specified in ieee->Result.
*/
/* ... */
}
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Undetected floating-point exceptions errors may result in lower program efficiency, inaccurate results, or software vulnerabilities. Most processors stall for a significant duration (sometimes up to a second or even more on 32-bit desktop processors) when an operation incurs a NaN (not a number) value.
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