Compile-time constant id

Question

Given the following:

template
class A
{
public:
    static const unsigned int ID = ?;
};

I want ID to generate a unique c

Answer 1

What I usually use is this:

template
void type_id(){}

using type_id_t = void(*)();

Since every instantiation of the function has it's own address, you can use that address to identify types:

// Work at compile time
constexpr type_id_t int_id = type_id;

// Work at runtime too
std::map types;

types[type_id] = 4;
types[type_id] = "values"s

// Find values
auto it = types.find(type_id);

if (it != types.end()) {
    // Found it!
}