External functions in IUS

I'm trying to do something very simple and yet... In IUS 9.12.UC2 I am creating a function thusly: create function total (val1 integer, num1 float) returning float; external name '/dir/IUSfuncs.so(IUSfuncs_total)' language c end function; My c function is pretty boneheaded: double IUSfuncs_total (long val1, double num1) { return (val1 * num1); } After compiling as a shared object, I try to run the following statement in dbaccess: select total(quantity, price) from table; And I get the error in the log: 13:42:06 Loading Module </dir/IUSfuncs.so> 13:42:06 C Language Module </dir/IUSfuncs.so> loaded 13:42:06 Assert Failed: Exception Caught. Type: MT_EX_OS, Context: mem 13:42:06 INFORMIX-Universal Server Version 9.12.UC2 13:42:06 Who: Session(1196, jgc@webser11, 10107, 0) Thread(1929, sqlexec, 0, 0) File: mtex.c Line: 183 13:42:06 Action: Please notify Informix Technical Support. 13:42:08 Blocking whole system for max 0 secs 13:42:08 VP 1 timed out during system block, releasing 13:42:08 Releasing VP 3 from system block 13:42:08 Releasing VP 7 from system block 13:42:08 Releasing VP 6 from system block 13:42:08 Releasing VP 8 from system block 13:42:08 Releasing VP 5 from system block 13:42:08 Releasing VP 4 from system block 13:42:23 See Also: /tmp/af.789a9fe, shmem.789a9fe.0 13:42:39 (-9791): ERROR: Routine execution trap -- procname=<total> procid=142 reason: Bad UDR return pointer I love the incredibly informative error message, Bad UDR return pointer? I have found the documentation to be of no help. I have tried numerous different options, such as changing the C datatypes, changing to pointers, but nothing gets me away from this same error. What is the ten-second step that I am missing?