How to know underlying type of class enum?

Question

I have a variable declared as:

enum class FooEnum: uint64_t {}

and I would like to cast to its base-type, but I don\'t want to hardcode the

Answer 1

Here is another approach for when underlying_type is not present. This method doesn't attempt to detect the signed-ness of the enum, just give you a type of the same size, which is more than enough for a lot of situations.

template
class TIntegerForSize
{
    typedef void type;
};

template<>
struct TIntegerForSize<1>
{
    typedef uint8_t type;
};

template<>
struct TIntegerForSize<2>
{
    typedef uint16_t type;
};

template<>
struct TIntegerForSize<4>
{
    typedef uint32_t type;
};

template<>
struct TIntegerForSize<8>
{
    typedef uint64_t type;
};

template
struct TIntegerForEnum
{
    typedef typename TIntegerForSize::type type;
};

Usage:

enum EFoo {Alpha, Beta};
EFoo f = Alpha;
TIntegerForEnum::type i = f;
TIntegerForEnum::type j = f;