pgsql-bugs(at)postgresql(dot)org writes:
> Using libpq to access a repote database from a c trigger function breaks.
Try linking libpq.a into your .so file. I think your references to
PQexec and so forth are being resolved to the
similarly-named-but-completely-different functions that exist in the
backend (see src/backend/libpq). There is no copy of client libpq in
the standard backend.
regards, tom lane