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 well a function can handle exceptions. The main levels are: 1. No-throw guarantee: The function guarantees not to 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 be left in an invalid state.

Can you explain the strong guarantee with an example?

Sure! The strong guarantee means that if an exception occurs, the state of the program remains unchanged. For example, consider a function that swaps two objects. If an exception occurs during the swap, the objects should remain in their original state. This can be achieved by using a temporary copy of the objects before performing the swap.

What about the basic guarantee?

The basic guarantee ensures that if an exception is thrown, the program will not be left in an invalid state, but some changes may have occurred. For instance, if you have a function that modifies a container, and an exception occurs during the modification, the container may be partially modified, but it will still be in a valid state.

How can I implement the no-throw guarantee?

To implement the no-throw guarantee, you can use techniques like using noexcept specifier in C++11 and later, which indicates that a function is not expected to throw exceptions. Additionally, you can ensure that all operations within the function are exception-safe, such as using only operations that are guaranteed not to throw.