Tracking CLDR version in collation definitions

[Thomas Munro]

On 9 September 2018 at 02:22, yuripv <yuripv at yuripv.net> wrote:
> Hi Thomas,
>
> I think this makes perfect sense, yes, and not aware of any other way of
> having the data version information.

Thanks for the feedback.  This is reassuring.  Yeah I've looked around a bit.

> There are some nits in the man page changes, but that can of course be taken
> care of during review.

Cool -- I will do some more work on this and post a differential.

> A bigger question is backwards compatibility as you seem to be changing the
> on-disk format -- I can't think of anything bad happening off the top of my
> head, just wondering if you had some ideas on it.

The on-disk format I propose is deliberately forwards AND backwards
compatible.  That region of the file is currently full of zeroes.  If
you call the new function for an older LC_COLLATE file, you just get
an empty string.  If you access a file that does have the new version
using an older libc, it ignores that region of the file.