Re: [TCLCORE] TIP 715 - Supported platforms and build environments for Tcl/Tk 9.1

[Keith N. <k.j...@us...>]

Hi All,

Requirements for Tcl/Tk 9.1: the 2038 problem.

The TIP proposes:

{
Where applicable, Tcl 9.1 requires
...
* C runtime / syscall with a 64 bit time_t structure to avoid the year
2038 Problem.
...
}

and also:

{
Obsolete platforms

The following platforms are explicitly marked as obsolete.
...
* Linux: 32-bit kernel versions prior to 5.6, released March 29, 2020.
...
}


The 2038 problem is painful, because despite plenty of warning, the
available fixes for 32-bit systems are embarrassingly recent.

The TIP proposes to obsolete 32-bit Linux kernel versions prior to 5.6
(released March 2020).  The reason is not given, but I guess it is
because these kernels lack system calls for 64-bit time.  I am not sure
that such obsolescence is necessary: if a host cannot handle the 2038
problem, there is no reason why a user should expect Tcl to have this
capability when running on that host.  Perhaps a warning could be
logged and also written to stderr whenever Tcl starts on a host that
has no system calls for 64-bit time, and also if commands such as
[clock], [file mtime] are used with inappropriate arguments or results.

The TIP also proposes a requirement for glibc >= 2.34, which is the
earliest version **ON 32-BIT SYSTEMS** that provides 64-bit time_t.
There is no problem with glibc on 64-bit systems, which has used 64-bit 
time as far back as glibc 2.0. On 32-bit systems running glibc 2.34,
compilation of glibc with 64-bit time_t is available but is **DISABLED
BY DEFAULT** for compatibility reasons - so a requirement for glibc
2.34 does not necessarily solve the problem: it will still be necessary
to test for the length of time_t.  Again, warnings could be emitted
rather than preventing the use of Tcl completely.

I suggest removing the mandatory requirement for 64-bit time_t,
replacing it with a recommendation, and if 64-bit time_t is not
available doing the best we can to either implement a workaround or
issue warnings.

Best wishes,

Keith.


On Tue, 2025-04-01 at 21:53 +0200, Harald Oehlmann wrote:
> Folks,
> TIP 715 was updated by the given information.
> 
> Thanks for any comment !
> 
> Harald
> 
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