C++ Exception Handling Interview Questions and Answers for 10 years experience

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C++ Exception Handling Interview Questions (10+ Years Experience)

  1. What is exception handling in C++?

    • Answer: Exception handling is a mechanism in C++ that allows programs to gracefully handle runtime errors or exceptional situations without terminating abruptly. It uses `try`, `catch`, and `throw` statements to separate error-handling code from the main program flow, improving code readability and robustness.

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

    • Answer: `try` block encloses code that might throw an exception. `throw` throws an exception object when an error occurs. `catch` blocks handle specific exception types thrown by the `try` block. Multiple `catch` blocks can handle different exception types.

  3. What are the different types of exceptions in C++?

    • Answer: C++ exceptions can be of any type, but common ones include standard library exceptions (e.g., `std::runtime_error`, `std::logic_error`, `std::exception`), custom exceptions (user-defined classes derived from `std::exception`), and exceptions thrown as built-in types (e.g., `int`).

  4. What is the difference between `std::exception` and its derived classes?

    • Answer: `std::exception` is a base class for standard exception types. Derived classes like `std::runtime_error` (for runtime errors) and `std::logic_error` (for logic errors) provide more specific exception types, allowing for more granular error handling.

  5. How do you create and throw a custom exception?

    • Answer: Create a class derived from `std::exception` (or another exception class). Override the `what()` method to provide a descriptive error message. Use `throw` to throw an instance of your custom exception class.

  6. Explain exception specifications (and why they are generally discouraged).

    • Answer: Exception specifications declared the exceptions a function could throw. However, they are largely deprecated because they made code brittle and complicated exception handling. Modern C++ prefers relying on exception handling mechanisms within the `try-catch` blocks.

  7. What is the importance of exception safety?

    • Answer: Exception safety ensures that resources are properly managed even when exceptions are thrown. This prevents resource leaks, data corruption, and program crashes. Key concepts include strong exception safety (guaranteeing data integrity), basic exception safety (guaranteeing resource safety), and nothrow exception safety (guaranteeing no exceptions are thrown).

  8. Describe RAII (Resource Acquisition Is Initialization) and its role in exception handling.

    • Answer: RAII is a C++ programming idiom where resource acquisition is tied to object initialization. Destructors automatically release resources when objects go out of scope, ensuring that resources are released even if exceptions are thrown, contributing significantly to exception safety.

  9. How can you handle exceptions in constructors and destructors?

    • Answer: Exceptions thrown in constructors should be handled carefully, potentially using a dedicated function to manage resource allocation and exception handling. Exceptions thrown in destructors are generally problematic, often leading to undefined behavior. Careful design is necessary to minimize the likelihood of exceptions in destructors.

  10. What is the difference between catching exceptions by value and by reference?

    • Answer: Catching by value creates a copy of the exception object. Catching by reference avoids the overhead of copying, particularly beneficial for large exception objects. Use reference for efficiency unless modification of the exception object within the `catch` block is required.

  11. Explain the use of `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's not listed in the exception specification (though exception specifications are generally discouraged). Both typically lead to program termination.

  12. Discuss the use of exception handling in multi-threaded applications.

    • Answer: Exception handling in multithreaded applications requires careful consideration of thread safety and synchronization. Exceptions thrown in one thread shouldn't corrupt data in other threads. Techniques such as mutexes, condition variables, and other synchronization mechanisms might be necessary to protect shared resources.

  13. How can you log exceptions for debugging purposes?

    • Answer: Log exception information (type, message, stack trace) within `catch` blocks using logging libraries (e.g., log4cxx, spdlog). Include details that aid debugging, such as timestamps and thread IDs.

  14. Explain the concept of exception handling best practices.

    • Answer: Catch specific exceptions rather than a generic `catch(...)`. Use RAII to manage resources. Keep `try` blocks as small as possible. Avoid exceptions for normal program flow control. Handle exceptions at the appropriate level. Log exceptions effectively. Test exception handling thoroughly.

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