[PATCH 1/1] Y2038: add function __difftime64

[Paul Eggert]

On 06/25/2018 03:32 PM, Albert ARIBAUD wrote:
> I replaced the original 32-bit difftime with a wrapper
> around the 64-bit time; and in both cases, there were two functions, on
> for each time size.

Yes, and all this is in the patch you posted in 
<https://www.sourceware.org/ml/libc-alpha/2018-06/msg00605.html>. What 
I'm not understanding is how the functions it defines (__difftime64 and 
__difftime on 32-bit hosts, and just __difftime on 64-bit hosts) 
interoperate the with user-defined macro (is it still _TIME_BITS? I 
can't recall) that specifies whether the user wants time_t is 64 or 32 
bits, and how they interoperate with the macro that Joseph Myers 
suggested was needed by the system to say whether a 32-bit time_t 
variant is supported.

In short, I'm still missing the bigger picture here.

> Since you want the changes in gnulib first, then I suspect I should
> provide branches above gnulib as well as above glibc? If so, what
> would you recommend as a good source on setting up a build and test
> setup for gnulib, similar to build-many-glibcs.py is for glibc?
>

Yes, it would be helpful to have this in Gnulib too. The basic idea is 
that Gnulib and glibc sources should be as close to each other as 
possible; preferably identical. You can build and test a Gnulib module 
by running './gnulib-tool --test modulename'; run './gnulib-tool --help' 
for more.