Re: About GSOC.

[Nathan Sidwell <nathan@acm.org>]

On 5/30/19 5:38 PM, Segher Boessenkool wrote:
> On Thu, May 30, 2019 at 07:08:45PM +0200, Martin Jambor wrote:
>> Interesting, I was also puzzled for a moment.  But notice that:
>>
>> int main ()
>> {
>>      _Float128 x = 18446744073709551617.5f128;
>>      _Float128 y = __builtin_roundf128 (x);
>> }
>>
>> behaves as expected... the difference is of course the suffix pegged to
>> the literal constant (see
>> https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gcc/Floating-Types.html).
>>
>> I would also expect GCC to use a larger type if a constant does not fit
>> into a double, but apparently that does not happen.  I would have to
>> check but it is probably the right behavior according to the standard.
> 
> 6.4.4.2/4: "An unsuffixed floating constant has type double."  I don't
> think your suggestion would be okay?

Not only that, but

1) there isn't a literal suffix to mean 'double', so one couldn't 
override that extended type.
2) how do you define 'doesn't fit'?  decimal 0.1 has a recurring binary 
representation.  Should that become the longest floating point type?

nathan

-- 
Nathan Sidwell