Best Practices for Exception Handling in C++

When using exception handling in C++, it's important to follow certain best practices to ensure clean, maintainable, and robust code. Here are some key best practices:

1. Use exceptions for exceptional conditions: Exceptions should be used to handle truly exceptional situations that are not part of the normal flow of the program. They should not be used for regular control flow or as a substitute for proper error handling.
2. Catch exceptions by reference: Always catch exceptions by reference (const&) to avoid unnecessary copying of exception objects. Catching by value can lead to slicing and loss of exception-specific data.
3. Be specific in exception handling: Catch specific exception types rather than using a generic catch(...) block. This allows for more targeted error handling and helps in identifying and fixing issues.
4. Handle exceptions at the appropriate level: Catch and handle exceptions at the level where you can meaningfully handle them. Don't catch exceptions at a low level if you can't handle them properly. Let them propagate to a higher level where they can be dealt with appropriately.
5. Avoid throwing exceptions from destructors: Destructors should not throw exceptions as it can lead to unexpected behavior and resource leaks. If a destructor needs to perform an operation that may throw, consider using a separate function for that purpose.
6. Use noexcept specifier judiciously: Use the noexcept specifier to indicate functions that are guaranteed not to throw exceptions. This can help in optimizing code and providing clear expectations to users of your code.
7. Provide informative error messages: When throwing exceptions, provide clear and informative error messages that describe the exceptional condition. This helps in debugging and understanding the cause of the exception.
8. Clean up resources in catch blocks: If an exception is caught, ensure that any acquired resources (memory, file handles, etc.) are properly cleaned up to avoid resource leaks.
9. Document exception behavior: Clearly document the exceptions that a function may throw and under what conditions they are thrown. This helps users of your code understand and handle exceptions appropriately.
10. Consider exception safety: Design your code with exception safety in mind. Ensure that your code maintains a consistent state and avoids resource leaks even in the presence of exceptions.

Here's an example that demonstrates some of these best practices:

1#include <iostream>
2#include <stdexcept>
3
4void processData(int data) {
5  if (data < 0) {
6    throw std::invalid_argument(
7      "Data cannot be negative");
8  }
9  // Process the data
10}
11
12int main() {
13  try {
14    processData(-1);
15  } catch (const std::invalid_argument& e) {
16    std::cout << "Invalid argument: "
17      << e.what() << "\n";
18    // Handle the exception and clean up
19    // resources if necessary
20  }
21}

1Invalid argument: Data cannot be negative

By following these best practices, you can write more robust, maintainable, and exception-safe code in C++.