enum to string in modern C++11 / C++14 / C++17 and future C++20

Question

Contrary to all other similar questions, this question is about using the new C++ features.

• 2008 c Is there a simple way to convert C++ enum to string?
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Answer 1

I have been frustrated by this problem for a long time too, along with the problem of getting a type converted to string in a proper way. However, for the last problem, I was surprised by the solution explained in Is it possible to print a variable's type in standard C++?, using the idea from Can I obtain C++ type names in a constexpr way?. Using this technique, an analogous function can be constructed for getting an enum value as string:

#include 
using namespace std;

class static_string
{
    const char* const p_;
    const std::size_t sz_;

public:
    typedef const char* const_iterator;

    template 
    constexpr static_string(const char(&a)[N]) noexcept
        : p_(a)
        , sz_(N - 1)
    {}

    constexpr static_string(const char* p, std::size_t N) noexcept
        : p_(p)
        , sz_(N)
    {}

    constexpr const char* data() const noexcept { return p_; }
    constexpr std::size_t size() const noexcept { return sz_; }

    constexpr const_iterator begin() const noexcept { return p_; }
    constexpr const_iterator end()   const noexcept { return p_ + sz_; }

    constexpr char operator[](std::size_t n) const
    {
        return n < sz_ ? p_[n] : throw std::out_of_range("static_string");
    }
};

inline std::ostream& operator<<(std::ostream& os, static_string const& s)
{
    return os.write(s.data(), s.size());
}

/// \brief Get the name of a type
template 
static_string typeName()
{
#ifdef __clang__
    static_string p = __PRETTY_FUNCTION__;
    return static_string(p.data() + 30, p.size() - 30 - 1);
#elif defined(_MSC_VER)
    static_string p = __FUNCSIG__;
    return static_string(p.data() + 37, p.size() - 37 - 7);
#endif

}

namespace details
{
    template 
    struct EnumWrapper
    {
        template < Enum enu >
        static static_string name()
        {
#ifdef __clang__
            static_string p = __PRETTY_FUNCTION__;
            static_string enumType = typeName();
            return static_string(p.data() + 73 + enumType.size(), p.size() - 73 - enumType.size() - 1);
#elif defined(_MSC_VER)
            static_string p = __FUNCSIG__;
            static_string enumType = typeName();
            return static_string(p.data() + 57 + enumType.size(), p.size() - 57 - enumType.size() - 7);
#endif
        }
    };
}

/// \brief Get the name of an enum value
template 
static_string enumName()
{
    return details::EnumWrapper::template name();
}

enum class Color
{
    Blue = 0,
    Yellow = 1
};


int main() 
{
    std::cout << "_" << typeName() << "_"  << std::endl;
    std::cout << "_" << enumName() << "_"  << std::endl;
    return 0;
}

The code above has only been tested on Clang (see https://ideone.com/je5Quv) and VS2015, but should be adaptable to other compilers by fiddling a bit with the integer constants. Of course, it still uses macros under the hood, but at least one doesn't need access to the enum implementation.