Re: more on undefined reference to 'pg_detoast_datum' and libpq

"D. Stimits" <stimits@comcast.net> writes:
> Apparently in PosgreSQL 7.2.3 (the Redhat 7.3 version, which has some 
> patching involved), pg_detoast_datum is defined in fmgr backend code, 
> but this function is not defined anywhere in any library, especially not 
> libpq.

Of course not; it's a backend function.  Your problem is that you are
trying to build a server-side function as though it were a client
application.  You're linking to an inappropriate set of libraries.
See the contrib modules for numerous examples of correct link setup
for server-side functions.
        regards, tom lane