Rob Newton írta:
  

Is there some way of building with Pg v8.0 ECPG lib and running on a
system with Pg v8.4 ECPG lib?  or vice versa? and is libecpg_compat
intended for that purpose?
    

You can build the src/interfaces/libpq and src/interfaces/ecpg/ecpglib
directories in the old version and install them side by side with the new
version. The 8.4 server works happily with the old ECPG client.