I knew about these previously, as quoted by Eddie in his post. Also read my comment at the end of his post as I actually tested the INTERFACE C pragma back in August 2001, this is documented in the Expoliting and protecting Oracle paper. My comment is here:
"A couple of comments. Normally FIPS stands for Federal Information Processing Standards, I don’t know but maybe its related?
Also on the Pragma interface C, if you read further in my first big Oracle paper (Expoliting and protecting Oracle) you will see that i tried to use the syntax myself but if fails with an ORA-6509 - ICD vector Processing error. I assumed at the time that Oracle implements a function call table. Like a table of structs that includes details for each function implemented as a pragma interface C call. This table or linked list would include function pointers for each C function, hence you cannot simply call your own C directly from PL/SQL unless you can update this table to add the address of the function you add. This is a great interface for calling C directly without the extproc overheads if only we coluld find a way to make it work..:-)"
Good post Eddie!