What are the different levels of exception safety in C++?

What are the different levels of exception safety in C++?

In C++, exception safety levels describe how functions handle exceptions. The main levels are: 1. No-throw guarantee: The function guarantees that it will not throw exceptions. 2. Strong guarantee: If an exception is thrown, the program state remains unchanged. 3. Basic guarantee: If an exception is thrown, some changes may occur, but the program will not crash.

Can you give examples of each level?

Sure! For the no-throw guarantee, consider a function that uses std::vector::push_back only when the vector is not full. For the strong guarantee, a copy operation that uses a temporary object can be an example, as it ensures the original object remains unchanged if an exception occurs. The basic guarantee can be seen in a function that modifies a member variable but may leave it in an inconsistent state if an exception is thrown.

How do I implement the strong exception safety guarantee?

To implement the strong exception safety guarantee, you can use the copy-and-swap idiom. This involves creating a copy of the object you want to modify and then swapping it with the original object. If an exception occurs during the copy, the original object remains unchanged.

What are the best practices for exception handling in C++?

Best practices include using RAII (Resource Acquisition Is Initialization) to manage resources, avoiding throwing exceptions from destructors, and ensuring that your functions clearly document their exception safety guarantees.