On 03/28/2018 11:54 AM, Charles A. Roelli wrote:
>
> -            time_t t = -67768038400665600;
> +            time_t t = -67768038400666600;

Thanks, I did that in Gnulib and propagated the result into Emacs master 
(see attached patch).

> And then I got the following in the output of ./configure:
>
>    checking whether localtime loops forever near extrema... ./configure: line 30561: 35760 Alarm clock             TZ=QQQ0 ./conftest$EXEEXT

Thanks for mentioning that; I attempted to suppress the "Alarm clock" 
stuff in the attached patch too.

> I will try to find the exact boundary of the hang again.  And the hang
> is timezone-dependent, so that complicates things too.

I think we should be OK here, as the test case uses UTC so that it is 
reproducible. The use of UTC could explain why the abovementioned 
numeric change was needed.