C++ Template Brain Fuck

brainfuck.cpp

struct badType;

template <typename TType = badType>
struct type_decl {
    static constexpr const char * format_string() {
        return (std::is_integral_v<TType>
            ? "%d"
            : (std::is_floating_point_v<TType>
                ? "%f"
                : (std::is_pointer_v<TType>
                    ? "%X"
                    : "")
                )
            );
    }
};

template <>
struct type_decl<const char *> {
    static constexpr const char * format_string() {
        return "%s";
    }
};

template <typename TType>
constexpr const char * get_fmt_string(TType value) {
    return type_decl<TType>::format_string();
};

template <typename ...TArgs>
void brain_fuck(TArgs ...args) {
    using unpacker_t = int[];

    string_buf<4096> buffer;
    
    int num_args = 0;

    (void)unpacker_t
    {
        (
            args,
            buffer.append("  arg[%d] : ", num_args++),
            buffer.append("%s : ", typeid(args).name()),
            buffer.append("%X : '", sizeof(args)),
            buffer.append(get_fmt_string(args), args),
            buffer.append("'\n"),
        0)...,
    };

    debugf("**** %d args ****\n", num_args);
    debugf(buffer);
}

brain_fuck("oh", "my", "god", 2.0f, 1, true);

/*
Output:

**** 6 args ****
  arg[0] : char const * : 4 : 'oh'
  arg[1] : char const * : 4 : 'my'
  arg[2] : char const * : 4 : 'god'
  arg[3] : float : 4 : '2.000000'
  arg[4] : int : 4 : '1'
  arg[5] : bool : 1 : '1'
*/