https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114126
--- Comment #5 from Sergio Peña <www3.spl at gmail dot com> ---
(In reply to Jakub Jelinek from comment #2)
> Why do you think this is a bug?
> #include <math.h>
> #include <stdlib.h>
> #include <stdio.h>
>
> int
> main ()
> {
> _Float128 f = tanf128 (M_PI_2f128);
> volatile _Float128 g = M_PI_2f128;
> g = tanf128 (g);
> char buf[128];
> strfromf128 (buf, 128, "%.34a", f);
> printf ("%s\n", buf);
> strfromf128 (buf, 128, "%.34a", g);
> printf ("%s\n", buf);
> }
> also prints
> 0x1.1c46bd57277993a2ee60193c957b000000p+114
> 0x1.1c46bd57277993a2ee60193c957b000000p+114
>
> M_PI_2q or M_PI_2f128 is
> 1.5707963267948966192313216916397513987...
> while pi/2 with larger precision is I think
> 1.5707963267948966192313216916397514420...
> so M_PI_2{q,f128} is rounded down, not up,
> so no wonder tanq/tanf128 is not inf.
Ok. It is posible I was wrong.
I have found this question:
https://stackoverflow.com/questions/54287492/why-didnt-i-get-tanpi-2-infinty-in-c
