func withVaList<R>(_: [CVarArgType], f: @noescape CVaListPointer -> R) Invoke f with a C va_list argument derived from args. Declaration func withVaList<R>(args: [CVarArgType], f: @noescape CVaListPointer -> R) -> R func withVaList<R>(_: VaListBuilder, f: @noescape CVaListPointer -> R) Invoke f with a C va_list argument derived from builder. Declaration func withVaList<R>(builder: VaListBuilder, f: @noescape CVaListPointer -> R) -> R