method signatures in C modules

I've got a question regarding method signatures in C modules. I've noted that add_function_constant() and quick_add_function both take arguments that specify the method signature. However, the form of the specification is different for each. I'm wondering a) whether there's a significant difference in the way they work and b) what these signatures are used for in c language modules if the function code normally does the argument checking.

I'm just wondering how much effort I need to put into signatures for methods in my auto-generated objective-c wrapper classes.

Hopefully someone can enlighten me. :)

Bill