I need to accomplish the following:

template<typename T>
f() {
    :
    return { -1 if T is of integral type, else nullptr }
}

In my particular use case, T could be one of four types:

int
Py_ssize_t  // ssize_t
Py_hash_t   // ssize_t

PyObject*   // PyObject is some C struct

This is the best solution I have so far:

template<typename T>
T test(typename enable_if<is_integral<T>::value, void*>::type = nullptr)
{ return -1; }

template<typename T>
T test(typename enable_if<is_pointer<T>::value, void*>::type = nullptr)
{ return nullptr; }

ideone

But is this using a sledgehammer to crack a nut?

My only objection is that it solves a wider problem scope, but I'm not sure whether it is complete without additional fiddling with std::decay.

I make a habit of resisting the temptation to complexify code so that it can also solve imaginary extensions of the problem scope at hand.

But in this case I can't see a simpler solution.