template <template <typename T, T a> class U, U<int, 42> b> struct C;

"ComeauTest.c", line 1: error: a nontype template parameter may not have class type
template <template <class T, T a> class U, U<int, 42> b> struct C;
^

template <template <typename T, T a> class U, typename V = U<int, 42> >
struct C
{
};

template <typename A, A a>
class X
{
};

int main()
{
  C<X> x;
  return 0;
}

template<typename T>
struct C
{
  typedef typename T::SpecialType SpecialType;

  C(SpecialType) {}
};

struct Check
{
  typedef U<int, 42> SpecialType;
};

typedef C<Check> CCheck;

ROP>>template <template <typename T, T a> class U, U<int, 42> b> struct C;
ROP>>

template <template <typename T, T a> class U, U<int, 42> *b> struct C;

__>template<typename T>
__>struct C
__>{
__>  typedef typename T::SpecialType SpecialType;

__>  C(SpecialType) {}
__>};

__>struct Check
__>{
__>  typedef U<int, 42> SpecialType;
__>};

__>typedef C<Check> CCheck;
__>

template <template <typename T, T a> class U *b> struct C{};
A<int, 42> a42;
A<char, 17> a17;
C<&a17> c17;
C<&a42> c42;

template <template <typename T, T a> class U *b> struct C{};
A<int, 42> a42;
A<char, 17> a17;
C<&a17> c17;
C<&a42> c42;

template <A<typename T, T a> *b> struct C{};

ROP>template <template <typename T, T a> class U *b> struct C{};
ROP>A<int, 42> a42;
ROP>A<char, 17> a17;
ROP>C<&a17> c17;
ROP>C<&a42> c42;
ROP>

template<typename T, T a>
struct A { };

template<typename T, T* p>
struct C { };

A<int, 42> a42;
A<char, 17> a17;
typedef C<A<int,42>, &a42> c42;
typedef C<A<char,17>, &a17> c17;

template<void* p>
struct C2 { };

typedef C2<&a42> c242;

__>>Не ясна ваша затея.

A a1;
A a2;

C<A> c1(a1);
C<A> c2(a2);

struct SingletonA {} // Как-нибудь реализуется

C<SingletonA > c1;

template<typename T, T a> struct A {};

template<typename T, T* ptr> struct C;

template<int a, A<int, a>* ptr> struct C<A<int, a>, ptr> {};
template<char a, A<char, a>* ptr> struct C<A<char, a>, ptr> {};

A<int, 1> a;
C<A<int, 1>, &a> c;