> > Be able to run a netbsd-4 or netbsd-3 userland on a netbsd-5 kernel.
quoted text
>
> I've come to believe that the ABI contract we should provide is  
> between the apps and libc/libpthread, i.e. at the .so level.  The  
> kernel to libc/libpthread interface should be allowed to be more fluid.
>
> Yes, I know that this will upset people who like static libraries, but  
> frankly, I don't really care.

That's not the only serious problem such a change would introduce.

As far as I understand it, such a change would *in practice* force a
synchronized upgrade of both kernel and user-land (mostly due to
"dragged-along dependencies"), as exemplified by a transition from 4.0
to -current, to preserve full functionality.  This makes it cumbersome
to say the least to back down of such an upgrade, if one were so
inclined, something we've supported in the past by having the ABI
contract between user-land and the kernel.  I think "operator-friendly
testing of new kernels" is a feature which is important to preserve.

Regards,

- Håvard