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

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100 C++ Exception Handling Interview Questions

  1. What are the benefits of using exceptions for error handling in C++?

    • Answer: Exceptions provide a structured and centralized way to handle errors, improving code readability and maintainability. They separate error handling logic from the main program flow, preventing deeply nested `if-else` statements. Exceptions also allow for handling errors that occur deep within function calls without requiring explicit error codes to be propagated up the call stack.

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

    • Answer: `try` is a block of code where exceptions might be thrown. `throw` is used to explicitly throw an exception object. `catch` is a block of code that handles specific exception types thrown within the associated `try` block. The `catch` block specifies the type of exception it can handle.

  3. What is the significance of exception specifications (deprecated)?

    • Answer: Exception specifications (e.g., `void foo() throw(int, std::string);`) were used to declare which exceptions a function could throw. However, they are considered deprecated in modern C++ because they lead to brittle code and are difficult to use correctly. Modern C++ relies on good documentation and coding practices instead.

  4. How do you handle exceptions that might occur during resource allocation (e.g., file opening, memory allocation)?

    • Answer: Use RAII (Resource Acquisition Is Initialization) with smart pointers (e.g., `std::unique_ptr`, `std::shared_ptr`) and other RAII classes. These automatically manage resources, ensuring they are released even if exceptions are thrown. For example, `std::ofstream` automatically closes the file on destruction.

  5. Explain the concept of exception safety. What are the different levels?

    • Answer: Exception safety refers to ensuring that resources are properly managed and data remains consistent even when exceptions are thrown. The levels are: Nothrow guarantee (no exceptions thrown), Strong guarantee (all operations are undone if an exception occurs), Basic guarantee (resources are released, but data might be inconsistent), No guarantee (no promises are made).

  6. Describe the use of `std::exception` and its derived classes.

    • Answer: `std::exception` is the base class for standard exception classes in C++. Derived classes such as `std::runtime_error`, `std::logic_error`, `std::invalid_argument`, `std::out_of_range`, etc., provide more specific exception types for different error conditions. Throwing specific exceptions improves error handling and diagnosis.

  7. How do you design a custom exception class? What should it include?

    • Answer: A custom exception class should inherit from `std::exception` or one of its derived classes. It should include a constructor to initialize error information (e.g., an error message), and optionally, methods to retrieve this information. Consider providing a `what()` method to return a descriptive error message.

  8. What is the difference between `catch(...)` and catching specific exception types?

    • Answer: `catch(...)` catches any exception. This is useful as a final catch-all to prevent unexpected program termination, but it should be used sparingly. Catching specific exception types allows for more precise error handling and improves code clarity and maintainability.

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