>>> Or at least there is such goal?
 >> Yes, it's a goal, [...].  Exceptions that I can remember or suspect
 >> are:

> One that bit me, but isn't on your list:

> * As of some release (2,0, I think it was), executables using nested
>   functions built on older versions would crash on the new release.

* xsrc?

I guess you are not worrying about ABI changing in xsrc libraries.
Am I right?  At least I had some problems with X applications
compiled for older NetBSD releases.
But I'm not sure, this was months ago, now I don't remember details.
Any way, this list of exclusions may be very interesting for end users.
Should it be part of NetBSD Guide or mentioned somwhere else?
Or at least a few words about
NetBSD's goals about binary compatibility in libc and other basic libraries.

-- 
Best regards, Aleksey Cheusov.