[fpc-devel] function IsInt64(Double): Boolean;

[J. Gareth Moreton]

Oh, minor error, the $43F constant is meant to be $43E.

Kit

On 04/05/2026 22:18, J. Gareth Moreton via fpc-devel wrote:
> The quickest way, I think, is to look at the exponent bits of the 
> Double.  Though it returns a false negative for -(2^63):
>
> function OXmlIsInt64(const aNumber: Double): Boolean;
> var
>   ExpMask: LongWord;
>   DoubleBits: LongWord absolute aNumber;
> begin
>   ExpMask := (DoubleBits shr 52) and $7FF;
>   Result := (ExpMask >= $3FF) and (ExpMask < $43F);
> end;
>
> I think that's correct - I haven't actually tested it though. Note it 
> only works for the standard IEEE 754 Double.
>
> Kit
>
> On 04/05/2026 21:48, Martin Frb via fpc-devel wrote:
>> On 04/05/2026 22:34, Ondrej Pokorny via fpc-devel wrote:
>>>
>>> I tried to switch overflow checks off:
>>> {$OVERFLOWCHECKS OFF}
>>>
>>> But obviously it doesn't help (it's a different exception).
>>
>> AFAIK:
>> You need to use SetExceptionMask, I think the below example should do:
>>
>>
>> procedure DisableFloatExceptions;
>> begin
>>   if FloatExceptionLock = 0 then begin
>>     EM := GetExceptionMask;
>>     SetExceptionMask(EM + [exInvalidOp, exDenormalized, exZeroDivide, 
>> exOverflow, exUnderflow, exPrecision]);
>>   end;
>>   inc(FloatExceptionLock);
>> end;
>>
>> procedure EnableFloatExceptions;
>> begin
>>   dec(FloatExceptionLock);
>>   if FloatExceptionLock <= 0 then begin
>>     FloatExceptionLock := 0;
>>     ClearExceptions(False);
>>     SetExceptionMask(EM);
>>   end;
>>
>> end;
>>
>>
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>>
>

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