Top C++ Exception Handling Interview Questions and Answers for 2 years experience

1. What is exception handling in C++?

   • Answer: Exception handling is a mechanism in C++ that allows you to gracefully handle runtime errors (exceptions) that occur during program execution. It prevents program crashes and allows for more robust and reliable code. It uses `try`, `catch`, and `throw` keywords.

2. Explain the `try`, `catch`, and `throw` keywords.

   • Answer: `try`: A block of code that might throw an exception. `throw`: Used to explicitly throw an exception object. `catch`: A block of code that handles a specific exception type thrown by the `try` block.

3. What are the benefits of using exception handling?

   • Answer: Improved error handling, separation of error-handling code from normal program flow, enhanced code readability and maintainability, increased program robustness and reliability.

4. What are some common exception classes in C++?

   • Answer: `std::exception`, `std::runtime_error`, `std::logic_error`, `std::out_of_range`, `std::invalid_argument` are some examples. Many custom exception classes are also created.

5. How do you create a custom exception class?

   • Answer: Inherit from a standard exception class (like `std::exception` or `std::runtime_error`) and add your own members and methods. Override the `what()` method to provide a descriptive error message.

6. Explain exception specifications (deprecated).

   • Answer: Exception specifications, using `throw()`, were a way to declare the types of exceptions a function could throw. However, they are considered deprecated in modern C++ because they often lead to issues with exception safety and are not recommended for use.

7. What is the difference between `catch(...)` and specific exception handlers?

   • Answer: `catch(...)` is a catch-all handler that catches any exception. Specific exception handlers (`catch(const std::runtime_error& e)`) catch only exceptions of the specified type or a derived type. Specific handlers are preferred for better error handling and debugging.

8. Explain exception handling and RAII (Resource Acquisition Is Initialization).

   • Answer: RAII ensures resources are automatically managed, often using smart pointers. When exceptions occur, RAII guarantees resource cleanup (e.g., closing files, releasing memory) even if exceptions are thrown, enhancing exception safety.

9. What is stack unwinding?

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

10. What are the different exception handling strategies?

    • Answer: Some strategies include: Try-catch blocks, exception specifications (deprecated), using RAII to manage resources, logging exceptions for debugging, handling exceptions at different levels of the application.

11. How can you prevent resource leaks in exception handling?

    • Answer: Use RAII with smart pointers (e.g., `std::unique_ptr`, `std::shared_ptr`) to automatically manage resources. This ensures that resources are released even if exceptions occur.

12. What is the difference between `std::exception` and `std::runtime_error`?

    • Answer: `std::runtime_error` is a more specific exception type derived from `std::exception`. It's typically used for errors that occur during program execution due to unexpected events or conditions, whereas `std::exception` is a more general base class for exceptions.

13. Explain the importance of exception safety.

    • Answer: Exception safety guarantees that in case of exceptions, the program's state remains consistent and no resources are leaked. There are different levels of exception safety: basic, strong, and nothrow.

14. How do you handle exceptions in multithreaded applications?

    • Answer: Careful consideration of thread synchronization is necessary. Exceptions in one thread should not interfere with the operation of other threads. Techniques like mutexes and condition variables help manage shared resources.

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