Re: [PATCH 1/1] Y2038: add function __difftime64

[Albert ARIBAUD <albert.aribaud@3adev.fr>]

Hi Bruno,

Le Thu, 05 Jul 2018 23:17:26 +0200, Bruno Haible <bruno@clisp.org> a
écrit :

> Albert ARIBAUD wrote:
> > I was under the impression that you wanted the
> > 64-bit-time stuff to go in gnulib before it went in glibc, so I don't
> > get what the "once glibc has such a macro" means. Can you elaborate on
> > what you had in mind?  
> 
> I can't speak for Paul, but for me the sequence of steps that produces the
> desired result with the least effort would be:
> 
>   1) glibc implements the 'time_t' type that depends on the value _TIME_BITS
>      defined at preprocessor level, like you described. Including support for
>      'gettimeofday', 'stat', 'fstat' and the like.
>      While doing so, pay attention that the implementation of mktime, strftime,
>      strptime, etc. can be compiled with a 32-bit time_t or a 64-bit time_t.
> 
>   2) gnulib modifies its year2038 module to define _TIME_BITS to 64 at configure
>      time, on platforms where glibc supports it.
> 
>   3) During the next source-code sync from glibc to gnulib, involving mktime.c
>      etc., the gnulib people (likely Paul) make sure that this source code can
>      still be used on non-glibc platforms with either 32-bit time_t or 64-bit
>      time_t. Usually this involves a couple of #ifs and conditional #includes.
>      These changes can then flow back into glibc. They won't have a functional
>      effect in glibc, therefore won't break the atomicity of step 1.
> 
> AFAICS, steps 3 could also be executed before step 2.
> 
> Bruno

Thanks for the detailed answer(s, including your previous one).

Do code syncs from glibc to gnulib happen on new glibc releases? If
they do, then my chick-and-egg problem remains (unless glibc accepts
pulling in only my glibc patch which add __time_64_t without changing
the public API, but that would amount to dead code.

Cordialement,
Albert ARIBAUD
3ADEV