cmake/Tests/CompileFeatures/cxx_variadic_templates.cpp

#if defined(__GNUC__) && ((__GNUC__ * 100 + __GNUC_MINOR__) < 407)
#  define OLD_GNU
#endif

#ifdef OLD_GNU
template <int... Is>
struct Interface;
#endif

template <int I, int... Is>
struct Interface
#ifdef OLD_GNU
  <I, Is...>
#endif
{
  static int accumulate() { return I + Interface<Is...>::accumulate(); }
};

template <int I>
struct Interface<I>
{
  static int accumulate() { return I; }
};

// Note: split this into a separate test if a
// cxx_variadic_template_template_parameters feature is added.

template <typename T>
struct eval
{
  enum
  {
    Matched = 0
  };
};

template <template <typename...> class T, typename... U>
struct eval<T<U...>>
{
  enum
  {
    Matched = 1
  };
};

template <typename...>
struct A
{
};
template <typename T>
struct B
{
};
template <typename T, typename U>
struct C
{
};
template <typename T, typename U, typename...>
struct D
{
};

// Note: This test assumes that a compiler supporting this feature
// supports static_assert. Add a workaround if that does not hold.
static_assert(eval<A<>>::Matched, "A Matches");
static_assert(eval<A<int>>::Matched, "A Matches");
static_assert(eval<A<int, char>>::Matched, "A Matches");
static_assert(eval<B<int>>::Matched, "B Matches");
static_assert(eval<C<int, char>>::Matched, "C Matches");
static_assert(eval<D<int, char>>::Matched, "D Matches");
static_assert(eval<D<int, char, bool>>::Matched, "D Matches");
static_assert(eval<D<int, char, bool, double>>::Matched, "D Matches");