template<typename _Foo> void temp_function(_Foo arg) { static_assert( ??? , "Fail"); }
template<> void temp_function(double arg) { /* code */ }
template<> void temp_function(int arg) { /* code */ }

template <typename _Tp>
struct FooStruct {
  __attribute__((aligned(16))) _Tp bar[256];
};

template <typename _Tp> class FooClass {
private:
  std::allocator<_Tp> alloc;
  FooStruct* ptr;

public:
  FooClass() { ptr = static_cast<FooStruct*>(alloc.allocate(256)); }
  ~FooClass() { alloc.deallocate(static_cast<_Tp*>(ptr), 256); }
};