Create serializable unique compile-time identifiers for arbitrary UDTs

Question

I need a general way to create unique compile-time identifiers for any custom C ++ types.
eg:

unique_id<my_type>::value == 0 // true
unique_id<other_type>::value == 1 // true  

I managed to implement something like this using preprocessor metaprogramming, the problem is that serialization is incompatible. For example, if you first unique_idcreate an instance template using other_type, then any serialization in previous versions of my program will be invalidated.

I searched for solutions to this problem and found several ways to implement this with incompatible serialization if the unique values ​​are compile time constants. If RTTI or similar methods are used, such as boost::sp_typeinfo, then the unique values ​​are obviously not compile-time constants and additional overhead is present. A special solution to this problem would be to create a unique_id instance in a separate header in the correct order, but this will cause an additional service code and template, which is no different from use enum unique_id{my_type, other_type};.

A good solution to this problem would be to use custom literals, unfortunately, as far as I know, no compiler supports them at the moment. The syntax will be 'my_type'_id; 'other_type'_id;using udl.

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Answer 1

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Answer 2

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// static detection
template <typename T>
size_t unique_id()
{
  static size_t const id = some_hash(typeid(T)); // or boost::sp_typeinfo
  return id;
}

// dynamic detection
template <typename T>
size_t unique_id(T const& t)
{
  return some_hash(typeid(t)); // no memoization possible
}

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Answer 3

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