64 bit time_t on riscv32

[Florian Weimer]

* Rich Felker:

> On Tue, Jan 16, 2024 at 04:46:17PM +0100, Florian Weimer wrote:
>> * Adhemerval Zanella Netto:
>> 
>> > My understanding was __USE_TIME_BITS64 would be required only for ABIs
>> > that actually would multiple time_t sizes and the glibc 64 bit time_t 
>> > supported was added on this assumption.  However, the design document 
>> > does state __USE_TIME_BITS64 would be defined even for architectures 
>> > where is does not require it.  I it was not really caught in development
>> > because the design creator was not really much involved at the time.
>> >
>> > I think it should be feasible to fix it, although backporting it would
>> > generate a quite large patch.
>> 
>> It will break applications that use __USE_TIME_BITS64 with glibc's
>> current semantics centered on time64 redirects (incorrectly, of
>> course—it's an internal macro).  I think the use in the kernel is
>> probably easier to address, and it has to be changed for compatibility
>> with other libcs anyway.
>
> If there are applications assuming __USE_TIME_BITS64 implies redirects
> and doing some hack around that, they really need to be fixed not to
> do that. It will break on musl with (not yet merged) rv32 port as well
> as any future 32-bit ports, which won't have any redirects because
> there is no legacy 32-bit time_t ABI to support.

That's actually not a problem because __USE_TIME_BITS64 is not defined
on rv32 et al. (hence the complaint about what the UAPI headers are
doing).

Thanks,
Florian