RTTI Overhead in C++

Question

What are the memory/performance overheads of enabling RTTI in a C++ program?
Can anyone please throw some light between the internal implementation of RTTI mechanism and

Answer 1

Please read appropriate section in this document.

To sum up:

• typeid (5.3.7): find vtable, through that find most derived class object, then extract type_info from that object's vtable. It is still very slow comparing with function call;

• dynamic_cast (5.3.8): find type_info as described above, then determine whether conversion is possible, then adjust pointers. Run-time cost depends on the relative position in the class hierarchy of two classes involved. Down- and cross-casts are very slow these days (though here you can find the article about possible (but restricted) constant-time implementation of dynamic_cast).