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

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

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.  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.

> 
>> Since the _TIME_BITS==32 world is going away anyway by 2038, it might
>> be better to leave the field types unchanged in that world, to lessen
>> compatibility glitches before that world gives up its ghost.
> 
> This is an on-disk format that doesn't change with -D_TIME_BITS=64.
> 
> Thanks,
> Florian
>