Re: [PATCH] LoongArch: Define __ARCH_WANT_NEW_STAT in unistd.h

[maobibo]

On 2024/5/15 下午10:25, Arnd Bergmann wrote:
> On Wed, May 15, 2024, at 09:30, maobibo wrote:
> > On 2024/5/11 下午8:17, Arnd Bergmann wrote:
> > > On Sat, May 11, 2024, at 12:01, Huacai Chen wrote:
> > >
> > > Importantly, we can't just add fstatat64() on riscv32 because
> > > there is no time64 version for it other than statx(), and I don't
> > > want the architectures to diverge more than necessary.
> > yes, I agree. Normally there is newfstatat() on 64-bit architectures but
> > fstatat64() on 32-bit ones.
> >
> > I do not understand why fstatat64() can be added for riscv32 still.
> > 32bit timestamp seems works well for the present, it is valid until
> > (0x1UL << 32) / 365 / 24 / 3600 + 1970 == 2106 year. Year 2106 should
> > be enough for 32bit system.
>
> There is a very small number of interfaces for which we ended up
> not using a 64-bit time_t replacement, but those are only for
> relative times, not epoch based offsets. The main problems
> here are:
>
> - time_t is defined to be a signed value in posix, and we need
>    to handle file timestamps before 1970 in stat(), so changing
>    this one to be unsigned is not an option.
>
> - A lot of products have already shipped that will have to
>    be supported past 2038 on existing 32-bit hardware. We
>    cannot regress on architectures that have already been
>    fixed to support this.
>
> - file timestamps can also be set into the future, so applications
>    relying on this are broken before 2038.
I see. And thanks for detailed explanation.

Regards
Bibo Mao
>        Arnd