Re: 128-bit integers can range only up to (2 ^ 63 -1)

On Tue, Jan 3, 2023 at 8:50 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> jian he <jian(dot)universality(at)gmail(dot)com> writes:
> > I am slightly confused by the int128 type. I thought the 128 bit integer
> > means range type will be upto 2 ^ 127 - 1.
> > Now just copy the above code and test the int128 range.
> > int128 can only up to 9223372036854775807 (2 ^ 63 -1).
>
> What's your grounds for claiming that?
>
> regards, tom lane
>

I did something like int128 a1 = 9223372036854775807 +
1;
I also did something like int128 a1 = (int128)9223372036854775807000;
I misread the warning. I should do the cast first.

The second expression has a warning. I guess because

> There is no support in GCC for expressing an integer constant of type
> __int128 for targets with long long integer less than 128 bits wide.
>
https://gcc.gnu.org/onlinedocs/gcc/_005f_005fint128.html