Dynamic function execution?

[Nick Johnson <arachnid@xxxxxxxxxx>]

Can anyone provide me with some direction on how to write a function  
I can load into postgres that will execute a function specified by  
OID (or regproc/regprocedure) at runtime, with type safety? I've been  
able to write such a function in C, but I was unable to figure out  
how to determine the parameters that the specified function expects,  
so I can prevent calling a function that doesn't match the expected  
signature (which segfaults postgres).

-Nick Johnson