Top C++ Exception Handling Interview Questions and Answers for internship

1. What is exception handling in C++?

   • Answer: Exception handling is a mechanism in C++ that allows you to gracefully handle runtime errors and other unexpected events without causing your program to crash. It separates error-handling code from the main program logic, improving code readability and maintainability.

2. What are the keywords used in C++ exception handling?

   • Answer: The main keywords are try, catch, and throw. try blocks contain code that might throw exceptions. catch blocks handle specific exception types. throw is used to explicitly throw an exception.

3. Explain the basic syntax of a try-catch block.

   • Answer: try { // Code that might throw exceptions } catch (exception_type e) { // Handle exceptions of type exception_type } catch (...) { // Handle any other exceptions }

4. What is the difference between `catch(exception& e)` and `catch(const exception& e)`?

   • Answer: `catch(const exception& e)` is generally preferred because it handles both const and non-const exceptions. `catch(exception& e)` only handles non-const exceptions.

5. What is the role of the ellipsis (...) in a catch block?

   • Answer: The ellipsis (...) acts as a catch-all, handling any exception type not caught by previous catch blocks. It's generally used as a last resort.

6. What are standard exception classes in C++?

   • Answer: The standard library provides several exception classes in ``, including std::exception (base class), std::runtime_error, std::logic_error, std::invalid_argument, std::out_of_range, etc.

7. When should you throw exceptions?

   • Answer: Throw exceptions for exceptional conditions – situations that are genuinely unexpected or represent errors. Don't use exceptions for normal control flow.

8. What is the difference between checked and unchecked exceptions? Does C++ have checked exceptions?

   • Answer: Checked exceptions (like in Java) require explicit handling, while unchecked exceptions don't. C++ does not have checked exceptions; all exceptions are unchecked.

9. Explain exception specifications (deprecated).

   • Answer: Exception specifications, using `throw()`, were used to declare which exceptions a function could throw. However, they are now considered deprecated and should be avoided because they can lead to unexpected behavior and are generally not beneficial.

10. What is RAII (Resource Acquisition Is Initialization)? How does it relate to exception handling?

    • Answer: RAII is a technique where resources (files, memory, locks, etc.) are managed by objects with destructors. When an exception occurs, destructors are automatically called, ensuring resources are released even if exceptions are thrown, preventing resource leaks.

11. How to handle exceptions thrown from dynamically allocated objects?

    • Answer: Use smart pointers (std::unique_ptr, std::shared_ptr) to manage dynamically allocated objects. Smart pointers automatically delete the objects when they go out of scope, even if exceptions are thrown.

12. Explain stack unwinding.

    • Answer: Stack unwinding is the process of cleaning up the stack when an exception is thrown. Destructors of objects on the stack are called in reverse order of their construction.

13. What is the difference between `std::terminate()` and `std::unexpected()`?

    • Answer: `std::terminate()` is called when an exception is thrown but no matching catch block is found. `std::unexpected()` is called when an exception is thrown that is not listed in an exception specification (though exception specifications are deprecated).

14. How do you create your own exception classes?

    • Answer: Derive your custom exception classes from std::exception or one of its subclasses. Provide a constructor to initialize an error message. Override what() to return a descriptive error message.

15. Describe exception safety guarantees.

    • Answer: Exception safety guarantees describe how a function behaves in the face of exceptions. The levels are: nothrow (no exceptions), basic (resources released), strong (guaranteed state), nothrow guarantee.

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