How to realize dynamic proxy in C++ language?

First of all see the short answer (nope) of CPallini above ;)

The long answer comes here.
A proxy is a design pattern that allows you to provide an interface to other objects by creating a wrapper class as the proxy. The wrapper class, which is the proxy, can add additional functionality to the object of interest without changing the object's code.

There is two kinds of proxy:

- Static Proxy (create a proxy object for every class)
- Dynamic Proxy (proxies are created dynamically through reflection)

The C++ language does not support reflection: Why does C++ not have reflection?

There are several problems with reflection in C++.

It's a lot of work to add, and the C++ committee is fairly conservative, and don't spend time on radical new features unless they're sure it'll pay off. (A suggestion for adding a module system similar to .NET assemblies has been made, and while I think there's general consensus that it'd be nice to have, it's not their top priority at the moment, and has been pushed back until well after C++0x. The motivation for this feature is to get rid of the #include system, but it would also enable at least some metadata).

You don't pay for what you don't use. That's one of the must basic design philosophies underlying C++. Why should my code carry around metadata if I may never need it? Moreover, the addition of metadata may inhibit the compiler from optimizing. Why should I pay that cost in my code if I may never need that metadata?

Which leads us to another big point: C++ makes very few guarantees about the compiled code. The compiler is allowed to do pretty much anything it likes, as long as the resulting functionality is what is expected. For example, your classes aren't required to actually be there. The compiler can optimize them away, inline everything they do, and it frequently does just that, because even simple template code tends to create quite a few template instantiations. The C++ standard library relies on this aggressive optimization. Functors are only performant if the overhead of instantiating and destructing the object can be optimized away. operator[] on a vector is only comparable to raw array indexing in performance because the entire operator can be inlined and thus removed entirely from the compiled code. C# and Java make a lot of guarantees about the output of the compiler. If I define a class in C#, then that class will exist in the resulting assembly. Even if I never use it. Even if all calls to its member functions could be inlined. The class has to be there, so that reflection can find it. Part of this is alleviated by C# compiling to bytecode, which means that the JIT compiler can remove class definitions and inline functions if it likes, even if the initial C# compiler can't. In C++, you only have one compiler, and it has to output efficient code. If you were allowed to inspect the metadata of a C++ executable, you'd expect to see every class it defined, which means that the compiler would have to preserve all the defined classes, even if they're not necessary.

And then there are templates. Templates in C++ are nothing like generics in other languages. Every template instantiation creates a new type. std::vector<int> is a completely separate class from std::vector<float>. That adds up to a lot of different types in a entire program. What should our reflection see? The template std::vector? But how can it, since that's a source-code construct, which has no meaning at runtime? It'd have to see the separate classes std::vector<int> and std::vector<float>. And std::vector<int>::iterator and std::vector<float>::iterator, same for const_iterator and so on. And once you step into template metaprogramming, you quickly end up instantiating hundreds of templates, all of which get inlined and removed again by the compiler. They have no meaning, except as part of a compile-time metaprogram. Should all these hundreds of classes be visible to reflection? They'd have to, because otherwise our reflection would be useless, if it doesn't even guarantee that the classes I defined will actually be there. And a side problem is that the template class doesn't exist until it is instantiated. Imagine a program which uses std::vector<int>. Should our reflection system be able to see std::vector::iterator? On one hand, you'd certainly expect so. It's an important class, and it's defined in terms of std::vector<int>, which does exist in the metadata. On the other hand, if the program never actually uses this iterator class template, its type will never have been instantiated, and so the compiler won't have generated the class in the first place. And it's too late to create it at runtime, since it requires access to the source code.
And finally, reflection isn't quite as vital in C++ as it is in C#. The reason is again, template metaprogramming. It can't solve everything, but for many cases where you'd otherwise resort to reflection, it's possible to write a metaprogram which does the same thing at compile-time. boost::type_traits is a simple example. You want to know about type T? Check its type_traits. In C#, you'd have to fish around after its type using reflection. Reflection would still be useful for some things (the main use I can see, which metaprogramming can't easily replace, is for autogenerated serialization code), but it would carry some significant costs for C++, and it's just not necessary as often as it is in other languages.