[PATCH] Y2038: provide kernel support indication

[Paul Eggert]

On 9/24/18 2:34 PM, Albert ARIBAUD wrote:
> Right now we can use the bits in __y2038_linux_support to indicate
> level of support (when positive) or reasons for not supporting (when
> negative). That's 31 distinct flags.

Rather than trying to shoehorn this into a single central integer or 
bitset that governs everything that could go wrong or right with Y2038, 
how about having a separate boolean (or whatever) variable for each 
feature? That way, only code that is worried about that feature needs to 
know about the variable, and it's easier to add or remove variables as 
the need for them is discovered or abandoned.

>    /* Linux kernel does or does not provide clock_gettime64 syscall.  */
>    #define Y2038_FEATURE_LINUX_CLOCK_GETTIME64 1
>
>    /* Linux kernel does or does not provide clock_settime64 syscall.  */
>    #define Y2038_FEATURE_LINUX_CLOCK_SETTIME64 2

Will there ever be a kernel that provides one syscall but not the other? 
We shouldn't need variables for each theoretically-possible platform, 
only for the platforms that exist, or are likely to.