How va_list and company work?

Currently i try to create a small trampoline for Objective-C IMP function. This function receive a variadic list of arguments. And i try to resend all parameters from trampoline to imp. So, va_start(ap,argument) return list of pointers. How parameters are allocated on stack and how c开发者_开发百科an i get it from there?

http://www.c-faq.com/varargs/handoff.html might help you out.