I'm not an expert on function pointers, but if his main program is just calling lib_archive(), then that function will have to exist, statically or dynamically, in the running process's symbol table. I suppose that function could then itself use function pointers, but the basic problem is knowing which actual algorithm the function should use, and if there are only four potential functions, then using function pointers seems more like an exercise in obfuscation.

Unless I'm missing a way in which they could be used. As I said, I'm not an expert.