Re: [boost] [TypeIndex] Peer review period for library acceptance begins, ending Thurs 21st Nov

On Thu, Nov 14, 2013 at 4:08 PM, Antony Polukhin wrote:

2013/11/14 Andrey Semashev

...

I think that these problems can be tackled by just having boost::type_index and boost::type_id. boost::type_index can implement the name functions we discussed and offer interfacing with std::type_info and implement workarounds for its bugs. boost::type_id (or preferably its variations) can solve problems with cv-qualification, references and visibility by wrapping the type before constructing boost::type_index.

The only reason for boost::type_info I see is to emulate RTTI when it's disabled. But as I see in the code, it is just an alias for template_info in this case. So perhaps we should just make it that - an alias to std::type_info or boost::template_info, depending on the configuration. This way it will just allow to use the type_info type portably, without preprocessor checks everywhere.

We are arguing about

class type_info: public std::type_info { ...};

vs

class type_info{ const std::type_info* ptr_; public: const std::type_info& get(); ... }; typedef ... std_type_info_if_exist_t;

Can you explain me once more, what are the advantages of the second solution?

No, I was thinking about something like this: // type_index/type_info.hpp namespace boost { #if HAS_RTTI typedef std::type_info type_info; #else typedef boost::template_info type_info; #endif } // type_index/type_index.hpp #include namespace boost { class type_index { boost::type_info const* m_type_info; public: explicit type_index(boost::type_info const&); boost::type_info const& get() const; // as previously discussed: const char* name() const; const char* raw_name() const; std::string pretty_name() const; }; #if HAS_RTTI template< typename T > type_index type_id() { return type_index(typeid(T)); } #else template< typename T > type_index type_id() { return type_index(template_info::construct<T>()); } #endif } // any.hpp #include class any { type_index m_type; public: boost::type_info const& type() const { return m_type.get(); } }; The benefit of this approach is that you don't have to write hacks on top of std::type_info and still get portable code (with and without native RTTI).