C has a va_list type that can be used together with a set of macros to iterate over variadic arguments to a call (passed by `...`).

Though it is technically possible for users the link upcalls and downcalls that have va_list parameters, using the given value, or creating a va_list value to pass as an argument requires quite intricate knowledge of the ABI and sometimes the particular native compiler implementation.

As such, it would be useful to add first class support for va_list, using a special VaList carrier type that is understood by the C linker implementations, as well as an API for creating such a VaList to pass to a native function, and an API to read a va_list passed from C to a Java method by upcall.