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What is Exception Handling in C++?

What is Exception Handling in C++?

Acting as an extension of the C programming language, C++ is a general-purpose programming language developed by Bjarne Stroustrup in 1985. Encompassing the concept of OOPs, C++ aids the programmer in implementing the ideas of classes and objects. Moreover, various programming languages and associated frameworks can be developed with C++. Besides promoting code reusability, C++ implements multiple programming paradigms. Through this blog, let us attempt to understand why the concept of exception handling is essential for a programmer.

Table of Contents:

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Introduction to Exception Handling

Introduction to Exceptional Handling

Exception handling in C++ is an essential concept in computer programming that enables developers to efficiently handle and respond to unexpected events or errors that may arise during the execution of a program.

The below-mentioned points provide detailed information about exceptional handling:

  • Exceptional handling in C++ provides a structured approach to handle exceptional conditions, ensuring the stability and reliability of the software.
  • Examples of exception handling can include divide-by-zero, file not found, or invalid input. Exception handling provides a mechanism to catch and handle these exceptions, thereby preventing the program from crashing or producing undesirable results.
  • Exception handling involves three key components: try, catch, and finally. 
  • In programming languages like Java and C++, exception handling is an integral part of the language syntax, with built-in keywords and constructs to facilitate the process.
  • Through the implementation of proper exception-handling techniques, developers can ensure that their programs gracefully handle errors, maintain stability, and provide informative feedback to users. 
  • Exceptional handling in C++ promotes robustness and improves the overall user experience. 
  • Furthermore, it helps in debugging and troubleshooting as exceptions are logged or reported, allowing developers to identify and resolve issues more efficiently.

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How Does Exception Handling Work?

How Does Exception Handling Work

Previously, we learned that exception handling is a concept in computer programming used to handle unexpected events. Below, we have mentioned its working mechanism.

The process of exception handling involves the following steps:

  • Throwing an Exception: When an exceptional situation occurs, an exception is raised or thrown. It can be done explicitly by the programmer or automatically by the system when certain predefined conditions are met, such as a division by zero or invalid input.
  • Catching the Exception: The code responsible for handling exceptions is enclosed within a try-catch block. The try C++ block has the code that may generate an exception, while the catch block specifies the actions to be taken when a specific type of exception occurs.
  • Handling the Exception: The catch block with a matching exception type is executed when an exception is thrown. The catch block contains the code to handle the exception, such as by showing an error message, logging the exception, or taking corrective actions.
  • Exception Propagation: If an exception is not caught within a specific catch block, it propagates up the call stack by the time an appropriate catch block catches it or reaches the program’s top level. If the exception is not caught, it results in program termination.

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How to Define New Exceptions in CPP?

To define a new exception in C++, you can follow these steps:

  • Decide on the type of exception you want to create. You can either derive your exception class from the standard exception class provided by the C++ Standard Library or create a custom exception class from scratch.
  • If you choose to derive from the standard exception class, include the <exception> header file in your code.
  • Define your exception class by creating a new class that inherits from std::exception or another suitable base class.

    Example using std::exception as the base class:
#include <exception>
class MyException : public std::exception
{
public:
    // Constructor with an optional error message
    MyException(const char* errorMessage) : m_errorMessage(errorMessage) {}
    // Override the what() function to return the error message
    const char* what() const noexcept override
    {
        return m_errorMessage;
    }
private:
    const char* m_errorMessage;
};
  • Provide any additional member functions or variables specific to your exception class if needed. In the example above, a constructor is defined to accept an error message and a private member variable is used to store the error message.
  • You can now throw instances of your exception class within your code using the throw keyword.
    Example

To catch and handle the thrown exception, you can use a try-catch block.

Example:

try
{
    myFunction();
}
catch (const MyException& e)
{
    // Handle the exception
    std::cout << "Exception caught: " << e.what() << std::endl;
}

By defining and throwing your custom exception, you can provide more specific error information and handle exceptional situations in a way that suits your application’s needs. Remember to include appropriate headers and namespace declarations as required.

Learn more about exceptional handling through our Exceptional Handling Tutorial in Java

Types of Exception Handling

Types of Exception Handling

By employing the different types of exception-handling techniques, developers can detect, handle, and recover from errors and exceptional situations in a controlled manner. Developers can utilize several exception-handling techniques to handle these situations, maintaining the stability and reliability of their software. Here are the various types of exception handling in C++:

  • Try-Catch: The try-catch block is the most common and widely used exception method. It involves placing the code that might throw an exception within a try C++ block and then catching and handling the exception within a catch block. This approach allows the program to continue execution even if an exception occurs, thus preventing the program from crashing.
  • Throws: The throw keyword is used to declare that a method may throw an exception. It is typically used when a method does not want to handle the exception itself but instead wants to pass it up the call stack to its caller. It allows for centralized exception handling at a higher level.
  • Custom Exceptions: Besides built-in exceptions, developers can create custom exceptions to handle specific exceptional situations unique to their applications. Custom exceptions can be derived from the built-in exception classes or existing custom exceptions, providing a way to encapsulate and handle specific errors more meaningfully and with more structure.
  • Finally: The finally block is used in conjunction with the try-catch block. It allows developers to specify code that will always be executed, irrespective of whether an exception occurs. It is particularly useful for releasing resources or cleaning up any allocated memory.

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Standard Exceptions in CPP

In C++, the Standard Library provides a set of predefined exception classes known as standard exceptions. These exceptions are defined in the <stdexcept> header and are intended to handle common error conditions that may occur during program execution. The standard exceptions are derived from the base class std::exception.

Here are some commonly used standard exceptions in C++:

  1. std::logic_error: This exception class is the base class for exceptions that indicate logical errors in a program. It includes subclasses like:
    • std::invalid_argument: Thrown when an invalid argument is passed to a function or constructor.
    • std::domain_error: Thrown when a mathematical function is called with an argument outside its valid domain.
    • std::length_error: Thrown when a length-related error occurs, such as when an object exceeds its maximum size.
  2. std::runtime_error: This exception class is the base class for exceptions that indicate runtime errors. It includes subclasses like:
    • std::overflow_error: Thrown when an arithmetic operation results in an overflow.
    • std::underflow_error: Thrown when an arithmetic operation results in an underflow.
    • std::range_error: Thrown when a value is outside the valid range of values.
  3. std::bad_alloc: This exception is thrown when a dynamic memory allocation fails, typically due to insufficient memory.
  4. std::out_of_range: This exception is thrown when an attempt is made to access an element outside the valid range of a container, such as an array or a string.
  5. std::exception: This is the base class for all standard exceptions. It provides a virtual member function called what() that returns a C-style string describing the exception.

These standard exceptions provide a convenient way to handle and propagate errors in a consistent manner. They can be caught using try-catch blocks, allowing you to handle specific error conditions and provide appropriate error messages or perform necessary cleanup operations.

It’s worth noting that in addition to these standard exceptions, you can also define your own custom exception classes by deriving from std::exception or any of its subclasses to handle application-specific error scenarios.

Advantages of Exception Handling

Advantages of Exception Handling

Exceptional handling in C++ offers several advantages that contribute to the overall robustness and reliability of software systems. Some of these advantages are mentioned below:

  • Error Management: Exception handling provides a structured approach to deal with errors, ensuring that they are handled gracefully rather than abruptly, which could cause the program to crash. It leads to an improved user experience and prevents data loss or corruption.
  • Debugging and Troubleshooting: Exception handling facilitates the identification and debugging of errors. When an exception is thrown, the program’s execution can be paused, and relevant information about the error, such as stack traces, can be logged or displayed. It provides assistance to developers in quickly identifying the root cause of the problem and resolving it efficiently.
  • Robustness and Resilience: It enables programs to gracefully recover from errors and continue executing, even in exceptional conditions. Developers can implement fallback mechanisms, alternate workflows, or appropriate error messages by catching and handling exceptions to ensure that the program remains operational.
  • Exception Propagation: Exceptions can be propagated across different layers of a software system, allowing for effective error reporting and handling at various levels. It promotes transparency and helps identify the exact location and cause of errors, leading to an efficient resolution.
    Program Flow Control: With exception handling, developers have greater control over the flow of their programs. They can anticipate and handle specific exceptions, thereby allowing for customized error-handling strategies based on the application’s requirements.
  • Code Maintainability: It promotes code modularity and maintainability by separating error-handling logic from regular program flow. Developers can encapsulate error-handling code within exception blocks, which helps them identify the errors

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Conclusion

In this blog, we briefly discussed exception handling in C++ and relevant information related to the topic. We learned about the types of exception handling and also came across their advantages. To ace the field of computer programming, you as a learner should understand the concept of exception handling which can help you to outshine in the interview process of the development field.

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About the Author

Senior Consultant Analytics & Data Science

Presenting Sahil Mattoo, a Senior Consultant Analytics & Data Science at Eli Lilly and Company is an accomplished professional with 14 years of experience across data science, analytics, and technical leadership domains, demonstrates a remarkable ability to drive business insights. Sahil holds a Post Graduate Program in Business Analytics and Business Intelligence from Great Lakes Institute of Management.