Er, just a sanity check on your answers:

> Just so I'm clear on this.  What acceptable combinations are there?  For 
>> instance:
>> 
>> 1.5.<current> userland + <current> kernel
> 
> 
> Yes.
> 
> 
>> 1.5.<current> userland + 1.5.<current> kernel
> 
> 
> No.

Er?

>> <current> userland + <current> kernel
> 
> 
> Yes.
> 
> 
>> etc.  There are incompatible userland (crtbegin, crtend) changes ...
> 
> 
> What is the problem here? 1.5 programs applications work still under
> NetBSD-current. There are only some system utilties which won't work.

The way .fini and .init sections were constructed was broken in <=1.5.x 
and fixed in current.  See bin/12865.  See kern/13615 (but skip to the end).

>> ... on the  trunk that I'm desperatly trying to avoid :-)
> 
> 
> In that case you should really run the release branch. NetBSD-current
> is not meant for production use. But if you want to use it you have
> to use it completely.

Thanks,
Andrew