[any] Unique type_info

[nowake@…]

Because typeid() does not return unique instance, we cannot use type_info instance pointer to compare types. And we cannot use type_info pointer with unorderd_*.

# unorderd_map is useful to implement boost::any's multi method (visitor) to dispatch in constant-time.

So I use static local variable in a function (like Singleton technique) to access type's type_info like this.

namespace boost {
    class any {
(snip)
        template<typename ValueType>
        static const std::type_info& any::typeinfo()
        {
            static const std::type_info& r(typeid(ValueType));
            return r;
        }

        const std::type_info & type() const
        {
            //return content ? content->type() : typeid(void);
            return content ? content->type() : typeinfo<void>();
        }
(snip)
        template<typename ValueType>
        class holder : public placeholder {
(snip)
            virtual const std::type_info & type() const {
                //return typeid(ValueType);
                return typeinfo<ValueType>();
            }
(snip)

[nowake@…]

boost::any that return unique type_info instance

[nasonov]

Anonymous who closed the bug was me.