In C++ programming, what is Run Time Type Information (RTTI) used for?

Introduction / Context:
Run Time Type Information, commonly called RTTI, is a feature in C++ that allows programs to discover the dynamic type of objects during execution. This is especially useful in polymorphic hierarchies where you work with base class pointers or references and may need to know the exact derived type at run time. This question asks what RTTI is used for in that context.

Given Data / Assumptions:

• We are using C++ with virtual functions and polymorphic classes.
• Objects may be referenced through pointers or references to a base class.
• We sometimes need to query the actual derived type or perform safe downcasts.

Concept / Approach:
RTTI enables two main facilities in C++. The first is typeid, which returns a std::type_info object describing the dynamic type of an expression when used with a polymorphic object, or the static type otherwise. The second is dynamic_cast, which performs a type safe cast that checks at run time whether the object being cast is of the requested type. If the cast is invalid, dynamic_cast returns null for pointers or throws an exception for references. These features rely on additional type information stored by the compiler and help ensure that operations on polymorphic objects remain safe.

Step-by-Step Solution:
Step 1: Recall that RTTI is associated with features like typeid and dynamic_cast in C++.Step 2: Recognise that these features allow you to examine or convert the dynamic type of an object safely at run time.Step 3: Option A states that RTTI provides information about an object type at run time for safe downcasts and type queries.Step 4: Options B, C and D describe uses unrelated to dynamic types.Step 5: Option E claims RTTI removes type checks, which is the opposite of its purpose, so option A is correct.

Verification / Alternative check:
Consider a hierarchy with class Base { virtual ~Base() {} }; and class Derived : public Base { };. If you have Base* p = new Derived; you can write if(Derived* d = dynamic_cast(p)) { /* use d */ }. Here dynamic_cast checks at run time whether p actually points to a Derived object. Similarly, typeid(*p) can reveal the dynamic type of the object. Both operations rely on RTTI data generated by the compiler.

Why Other Options Are Wrong:
Option B talks about local variables, which are not the focus of RTTI. Option C refers to line counts in source files, which is a documentation issue rather than a type system feature. Option D introduces logging for performance statistics, which is unrelated to RTTI. Option E misrepresents RTTI as an optimisation that removes type checks, while in reality it enables additional safety checks at run time.

Common Pitfalls:
Developers sometimes overuse RTTI and dynamic_cast where virtual functions or proper design of interfaces would be cleaner. Another pitfall is disabling RTTI through compiler options and then expecting typeid or dynamic_cast to work fully. While RTTI is useful, it should be applied judiciously and not as a substitute for good polymorphic design. For exam questions, remember that RTTI is about obtaining type information and performing safe casts at run time.

Final Answer:
It provides information about an object type at run time, enabling safe downcasts and type queries using mechanisms such as typeid and dynamic_cast.