libhello DLL in autobook

[Kevin Ryde]

I was looking at the libhello DLL example, with a view to doing
something similar, and wondered whether hello.h needed to be told
whether it's being used within the libhello build before it pays
attention to DLL_EXPORT.

If hello.h was used by another package building a libfoo DLL with
libtool, the DLL_EXPORT there would want to apply to symbols exported
from libfoo, and hello.h would want to mark libhello symbols as
imports.  Or am I missing something basic and this is not the case,
or never happens?