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

[J. Gareth Moreton]

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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