Re: portable way to get highest bit set?

Ben Bacarisse ha scritto:
> jak <[email protected]> writes:
> 
>> Ben Bacarisse ha scritto:
>>> jak <[email protected]> writes:
>>>
>>>> candycanearter07 ha scritto:
>>>>> Hi,
>>>>> What is the best/most portable way to get the highest bit set?
>>>>> ie. 011010001
>>>>> to  010000000
>>>>
>>>> Hi,
>>>> I don't think it's the best but the most portable could be the
>>>> mathematical approach:
>>>>
>>>> #include <stdio.h>
>>>> #include <math.h>
>>>>
>>>> int main()
>>>> {
>>>>       unsigned long val = 3000, ret;
>>> Test case: val = 0xFFFFFFFFFFFFFFFF
>>
>> This is due to the approximation of the floating point:
> 
> I know the reason.  I was just pointing out that you need to at least
> test the boundary cases!
> 

I am sure you knew and I have verified that the problem persists up to
"~0UL - 10000" but I don't find an elegant way, type independent, to
work around... just adding an 'if' or a ternary operator.