C++ get declared type info

Useful for automating some compile-time initialization in combination with consteval or constexpr:

#include "string.h"

#include "stdlib.h"

#include <iostream>

template <class T>

constexpr std::string_view type_name()

{

    using namespace std;

#ifdef __clang__

    string_view p = __PRETTY_FUNCTION__;

    return string_view(p.data() + 34, p.size() - 34 - 1);

#elif defined(__GNUC__)

    string_view p = __PRETTY_FUNCTION__;

#  if __cplusplus < 201402

    return string_view(p.data() + 36, p.size() - 36 - 1);

#  else

    return string_view(p.data() + 49, p.find(';', 49) - 49);

#  endif

#elif defined(_MSC_VER)

    string_view p = __FUNCSIG__;

    return string_view(p.data() + 84, p.size() - 84 - 7);

#endif

}

static char x[] = "Test";

int main() {

    std::cout << type_name<decltype(x)>() << "\r\n";

    std::cout << type_name<std::decay<decltype(x)>::type>();

}