 /// `withVaList` as intended.
 @warn_unused_result
 public func getVaList(args: [CVarArg]) -> CVaListPointer {
-  let builder = VaListBuilder()
+  let builder = _VaListBuilder()
   for a in args {
     builder.append(a)
   }


/// An object that can manage the lifetime of storage backing a
/// `CVaListPointer`.
final public class VaListBuilder {

  func append(arg: CVarArg) {
    // Write alignment padding if necessary.


/// An object that can manage the lifetime of storage backing a
/// `CVaListPointer`.
final internal class _VaListBuilder {

  struct Header {
    var gp_offset = CUnsignedInt(0)
