Re: [PATCH] login: Use unsigned 32-bit types for seconds-since-epoch

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella Netto:

> On 04/04/24 02:09, Florian Weimer wrote:
>> * Paul Eggert:
>> 
>>> On 4/3/24 11:39, Florian Weimer wrote:
>>>> For consistency,
>>>> if there is a 64-bit architecture that is coinstallable, define
>>>> __WORDSIZE_TIME64_COMPAT32 to 1 on the 32-bit architectyre as well.
>>>
>>> Could you explain the advantage of consistency here? User code almost
>>> invariably assignes ut_tv.tv_sec to time_t (this is true of every
>>> instance I found of ut_tv in Gnulib source code, for example). So
>>> changing this field's type on platforms where time_t is 32 bits will
>>> likely be ineffective in practice, and might cause more problems than
>>> it cures.
>> 
>> Few applications with a 32-bit time_t will work once there is a value in
>> this field with the MSB set.  So the relevant case is applications that
>> were built with -D_TIME_BITS=64, and there the consistent behavior with
>> the 64-bit architecture helps.
>
> This helps only architectures with __WORDSIZE_TIME64_COMPAT32, so it does
> not really solve the issue for all legacy platforms.

We can add more __WORDSIZE_TIME64_COMPAT32=1 definitions.

> I still prefer if we just deprecate this whole interface, since from
> other legacy ABI history (non-LFS interface) programs will keep using
> it until something breaks.

I don't disagree, I just want to give distributions the option to
backport a reviewed patch with a workaround that appears not to require
much application porting.  I believe many of us are preparing toolchains
for distributions that are running close to the 2038 cliff.

Thanks,
Florian