Add type_key<T>() to generate a unique key for a type #1249
Description
The key returned from type_key<T>() must be unique for each type within an executable.
Possible implementation:-
#if ETL_USING_CPP11
using type_key_t = void*;
template <typename T>
struct type_anchor
{
static constexpr int value = 0;
};
template <typename T>
constexpr const void* type_key() noexcept
{
return &type_anchor<T>::value;
}
#else
// For C++98/03
typedef void* type_key_t;
template <typename T>
const void* type_key()
{
static char anchor; // unique per T
return &anchor;
}
#endif