I found the core::ffi::VaList and core::ffi::VaListImpl but I really don't understand how to use it.
fn calling_c_va_li-st<T,U>(args1: T, args2: U){
// Create VaList called va_list_args. How to do this?
c_fct(&mut va_list_args as *mut core::ffi::VaList);
}
This is how you use variadics in rust, but it's only allowed for extern functions. The compiler deals with the VaList internally, so you (presumably) don't have to worry about it.
A function taking a valist and a variadic function are actually different things from a calling convention perspective, so just declaring the function as variadic doesn't work iirc.