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Re: Fourth draft of the Y2038 design document

On Wed, 28 Sep 2016, Albert ARIBAUD wrote:

> - make Y2038-safe kernel provide a new syscall which tells at run time
>   what features the kernel supports, e.g. does it support 64-bit time,
>   32-bit time, both? [the need could be more generic than just time
>   support, so I tought such a syscall already existed, but I have not
>   found any in the current syscalls list -- I might have missed it
>   though]

There will be lots of syscalls added with the 64-bit time support.  If 
they are all added in the same kernel version, glibc can have a single 
internal variable for whether 64-bit time support is available in the 
kernel (set the first time it tries using such a syscall, used to tell 
whether to try such syscalls in future).

> A Y2038-safe GLIBC would thus detect when it runs on a non-Y2038-safe
> kernel (syscall absent or returning a value which amounts to 'no
> 64-bit time support built in kernel') and could bail out with an
> explicit message.

But it shouldn't bail out; it should just use the existing syscalls and 
translate as needed when the user called the 64-bit time interfaces.

Joseph S. Myers

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