Creating a C Function

I am trying to create a function using C, but I am having trouble getting
Postgres to execute it. If I call the function from a C program, it works
fine, but pgsql gives me this:

ERROR: Load of file /usr/local/pgsql/obj/gen_username.so failed: Unable
to resolve symbol

Perhaps I am failing in the compilation/linking process. Does anyone
happen to have a generic make file for Linux (2.0.32, pgsql v. 6.3.2)?
The file is there, and the complete tree (including the .so) is world
readable/executable.

In case it matters, here is the interface for the function:

text * gen_username (text *lname, text *fname);

Any ideas? Thanks...

Jason Lee screech(at)screech(dot)org
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