[PATCH] Correct timespec implementation [BZ #26232]

[Florian Weimer]

* H. J. Lu:

> There are
>
> time_t
> support_timespec_ns (struct timespec time)
> {
>   time_t time_ns;
>   if (INT_MULTIPLY_WRAPV(time.tv_sec, TIMESPEC_HZ, &time_ns))
>     return time.tv_sec < 0 ? TYPE_MINIMUM(time_t) : TYPE_MAXIMUM(time_t);
>   if (INT_ADD_WRAPV(time_ns, time.tv_nsec, &time_ns))
>     return time.tv_nsec < 0 ? TYPE_MINIMUM(time_t) : TYPE_MAXIMUM(time_t);
>   return time_ns;
> }
>
> Even if support_timespec_ns is changed to return long long, we still
> may need to keep
>
>  time_t time_ns;
>
> for
>
>    if (INT_MULTIPLY_WRAPV(time.tv_sec, TIMESPEC_HZ, &time_ns))
>
> and
>
>   if (INT_ADD_WRAPV(time_ns, time.tv_nsec, &time_ns))
>
> It looks odd to return long long here.

Why?

You can use the GCC built-ins for checked arithmetic, they support mixed
types.

Thanks,
Florian