C++ Throw

Throw is a fundamental keyword in C++ that is used in exception handling, which is a system that allows a program to respond to unexpected events or faults during runtime in a controlled and organised manner. Exceptions signal when anything unexpected or incorrect happens while the program is running.

When an error or unusual event occurs, the throw keyword is used to cause an exception within a block of code explicitly. When an exception is raised, the program looks for a suitable exception handler to manage it and fix the problem. The programme passes control to an appropriate handler to handle the uncommon case if one is located.

keywords are Used in C++ for Handling Exceptions

Three primary keywords are used in C++ for handling exceptions:

1. Try: This term identifies a section of code that permits exception throwing. It is followed by a section of code called the "try block" that keeps monitoring for errors.
2. Throw: To throw an exception directly, use this keyword. The expression or object representing the exception being thrown is placed after it.
3. Catch: This keyword designates a section of code known as the "catch block" that deals with a particular kind of exception. Control is sent to the appropriate catch block for treatment if an exception is thrown in the related try block and matches the given type.

The ability to effortlessly manage mistakes and rare circumstances using exception handling is essential for building strong and dependable programmes. This increases the program's stability and maintainability. Throw allows programmers to modify and propagate exceptions, enabling efficient error handling in C++ programs.

While using C++'s exception-handling features, it's important to keep the following in mind:

• Try-Catch Blocks: Try and catch blocks are commonly used in the organisation of exception handling. Try and catch blocks are used to separate code that handles exceptions from that that could throw them.
• Throwing Exceptions: When a unique circumstance or error occurs, you may use the throw keyword to throw an exception explicitly. A word or object representing the exception is placed after the throw command.
• Exception Types: Objects of classes descended from the std::exception class, or its subclasses represent exceptions in C++. If necessary, you can make your exception classes.
• Catch Handlers: Exceptions are caught and handled using catch blocks. Within brackets, they describe the kind of exception they can handle. The appropriate catch block is run in response to an exception of the given type being thrown.
• Multiple Catch Blocks: To handle different sorts of exceptions or to offer other error-handling logic for each exception type, you may have numerous catch blocks following a single try block.
• Catch-All Blocks: A catch-all block may be combined with a catch to catch any exception type. Catch-all blocks should, however, be used with caution because they can make debugging and maintenance more difficult.
• Exception Propagation: An exception will move up the call stack to the closest enclosing try block in an outside function if it is not captured in a catch block within the current function. This enables you to deal with exceptions in the proper way.
• Cleanup using Resource Acquisition Is Initialisation (RAII): Resource Acquisition Is Initialisation (RAII) is a C++ programming approach that entails managing resources using constructor and destructor calls. Even in the presence of exceptions, RAII can aid in ensuring resource cleaning.
• Avoiding Resource Leaks: It's crucial to ensure that resources are appropriately released in catch blocks or destructors when working with resources like memory, files, or other external things to avoid resource leaks.
• Custom Exception Classes: To provide relevant error messages and to distinguish between various error situations, think about building custom exception classes for your application-specific failures.
• Exception Safety: When writing code, keep exception safety in mind. This includes ensuring that objects are maintained consistently, even if an exception is raised when creating or modifying them.
• Logging and Reporting: To help with debugging and to provide users with clear error messages, it's frequently beneficial to log or report exceptions.
• Error Handling Approach: Carefully consider your error handling approach, determining whether to fix mistakes. Gracefully end the program. Notify the user of issues.

Example code for C++ throw:

#include<iostream>

#include<stdexcept>

//function that simulates dividing two numbers and handling exceptions

double customDivide(double dividend, double divisor) {

// Check if the divisor is zero

if (divisor == 0.0) {

// Throw a runtime error if division by zero is detected

throw std::runtime_error("Division by zero is not allowed.");

    }

// Return the result of the division

return dividend/divisor;

}

int main() {

double numerator, denominator;

// Get user input for the numerator

std: :cout << "Enter numerator: ";

std: :cin >> numerator;

// Get user input for the denominator

std: :cout << "Enter denominator: ";

std: :cin >> denominator;

try {

// Attempt the division and catch any exceptions

double result = customDivide(numerator, denominator); 

std: :cout << "Result of the division: " << result << std::endl;

    } catch (const std::exception& e) {

// Handle and display any exceptions that occur during the division

std: :cerr << "Error: " << e.what() << std::endl;

    }

return 0;

}

Output:

Explanation:

The provided C++ code is an example of exception handling, an essential component of programming that enables kind error handling. This code's main objective is to divide while ensuring that division by zero is handled correctly.

A customDivide function in the code is in charge of carrying out the division. Dividend and divisor are two double values that it requires as inputs. Using the conditional statement if (divisor == 0.0), the code first determines if the divisor equals zero. Since division by zero is indefinable in mathematics, this check is crucial to avoiding a mathematical mistake.

If the divisor is zero, the program throws an exception using throw std::runtime_error("Division by zero is not allowed."). This code generates a custom error message and a runtime exception clearly stating the problem.

Two double variables, denominator and numerator, are declared in the main function to hold input values from the user. Using std::cout and std::cin, the program invites the user to input these values.

The division operation is included within the try block. The numerator and denominator values are sent to the customDivide function inside this block, and the output is placed in the result variable. The programme may carry out the division while preparing for any potential exceptions that might be thrown because of the try-catch technique.

When to Throw a C++ Exception

Exceptions should be thrown in C++ when a unique situation or error comes up that disturbs the regular flow of programme execution and cannot be handled gracefully at the time the fault occurs. The use of exceptions enables better organised and controlled handling of error conditions and extraordinary circumstances. The following situations frequently call for throwing a C++ exception:

• Division by Zero: To avoid unexpected behaviour, throwing an exception while attempting to divide an integer by zero is a good idea.
• File I/O Errors: Exceptions can be thrown when file operations like opening, reading, or writing fail for reasons like missing files or insufficient permissions.
• Invalid Input: Throwing an exception might signify that the input is unacceptable if a function gets invalid input arguments that it cannot process.
• Failures in Resource Allocation: A std::bad_alloc exception is frequently issued when dynamic memory allocation (new or malloc) fails due to memory depletion.
• Out-of-Range Access: It is permissible to throw an out-of-range exception (such as std::out_of_range) when attempting to access an element that is outside the boundaries of an array or container.
• Custom Error Conditions: To indicate application-specific problems, developers can create their custom exception classes. For instance, you may create the BankException class in a banking application to handle money-related issues.
• Unexpected or Unrecoverable Situations: Exceptions can be raised to gracefully end a programme when it runs into situations that are unexpected to happen during regular programme execution and are not recoverable, including damaged data or internal logic faults.
• Resource cleanup: Exceptions can be used, for example, in the destructor of a resource management class, to make sure that resources like file handles, network connections, or allocated memory are released correctly.
• These are some scenarios where the exception or C++ throw will be used. By using this throw, we can raise an exception when it arises.

Advantages of C++ Throw

The throw exception handling technique in C++ has the following benefits:

1. Error Handling: throw lets you communicate effectively and manage errors and unusual situations. This is crucial in circumstances when mistakes could occur but cannot be detected just by return values or status codes.
2. Structured Error Handling: C++ exceptions give a structured method of error handling. Error-handling logic may be contained using try, catch, and throw, which makes it more logically structured and more straightforward to maintain.
3. Separation of Concerns: By throwing exceptions, you can separate the logic that handles errors from the rest of the program. This division improves the readability and maintainability of the code.
4. Custom Error Types: C++ enables you to define your exception types by deriving classes from existing exception classes or std::exception. As a result, it is possible to express certain error circumstances meaningfully.
5. Stack Unwinding: C++ ensures the stack is unwound correctly when triggering an exception. This indicates that after the programme leaves the current scope, calls to local object destructors are made in the opposite order of construction. As a result, resource clearing is guaranteed, and resource leaks like memory leaks are avoided.
6. Error reporting: Through the constructor parameters, exceptions could carry context or extra information about the error. Error reporting and debugging may benefit from this information.
7. Hierarchical Exception Handling: C++ allows for the handling of hierarchical or nested exceptions. More precise error handling is possible because of the call stack's ability to collect exceptions at various levels.
8. Robustness: By enabling programmes to recover gracefully from unexpected events, exception handling increases programme robustness. It helps to guarantee that vital resources are released appropriately and prevents crashes.
9. Support for Typical Libraries: Standard exception classes for common problem cases are provided by the C++ standard library, including std::runtime_error, std::logic_error, and std::out_of_range. This makes writing reliable and portable code simpler.
10. Polymorphism exception management: Because exceptions are objects, polymorphism exception management is possible in C++. By using a base class reference, such as std::exception, you may catch exceptions and manage them according to their actual derived types.
11. Clarity: By isolating regular control flow from error-handling logic, exception handling may make code more legible. This may result in more understandable, cleaner code.

Disadvantages of C++ Throw

While C++ exception handling has many advantages, there are several disadvantages and concerns that developers should be aware of:

1. Performance cost: When exceptions are thrown frequently, exception handling might cause performance cost. Compared to other error-handling techniques like error codes, unwinding the call stack to locate the proper catch block might be an extended process.
2. Complex Control Flow: When managing exceptions, particularly in deeply nested try-catch blocks, complex control flow might result, making it more difficult to understand the logic of the program.
3. Resource Leaks: When exceptions are handled incorrectly, resource leaks may occur. Memory leaks or other resource-related problems may result from an exception that is raised but not handled or from the improper release of resources in exception-handling code.
4. Limited in Real-Time Systems: The unpredictable behaviour that exceptions introduce might be undesirable in real-time or embedded systems where predictable and constrained execution periods are essential. Some real-time systems prevent entirely exceptions.
5. Portability: Exception-handling algorithms might not be completely transferable between systems or compilers. Although the C++ standard offers a uniform foundation, there may still be differences in handling exceptions.
6. Portability: Exception-handling algorithms might not be completely transferable between systems or compilers. Although the C++ standard offers a uniform foundation, there may still be differences in handling exceptions.
7. Code Size: The executable size can be increased by exception-related code, such as exception tables and unwinding algorithms. This may be an issue in circumstances with limited memory or storage.

Conclusion

In simple terms, a C++ throw is a signal you may use to indicate in your program, "Something unexpected or wrong happened!" It serves as a means of informing your program's code and other components of a problem. Throwing an exception is equivalent to declaring, "I can't handle this situation here; someone else needs to handle it."

Throwing exceptions, while helpful in addressing mistakes and unexpected events, should be done with caution. Raising exceptions incorrectly or too frequently might make your programme slower and more difficult to understand. Therefore, use throw properly to strengthen your code when it runs into issues that require particular attention.