exceptionsafe

Exceptionsafe is a design principle in software engineering that concerns how code behaves when exceptions interrupt normal control flow. An exceptionsafe component aims to maintain program correctness, preserve invariants, and avoid resource leaks in the presence of errors.

Common levels of exception safety include: no-throw, which guarantees that a function will not throw; strong exception safety, where if an exception occurs, the system state is unchanged as if the operation had never started; and basic exception safety, where invariants are preserved and resources are not leaked, but the final state after an exception may differ. A function may provide no guarantee about its post-state beyond preserving invariants.

To achieve exceptionsafe behavior, developers rely on techniques such as RAII (resource acquisition is initialization) and smart pointers, which ensure automatic cleanup; using operations that offer stronger guarantees; structuring mutations so that changes can be rolled back or isolated; avoiding throwing in destructors; writing exception-safe constructors; and, in languages like C++, annotating functions with noexcept to express an explicit no-throw intent.

The term is most commonly discussed in the context of C++, but the underlying principle applies across languages with exceptions. Different languages provide different mechanisms for expressing guarantees and handling failures, yet the objective remains the same: minimize unintended side effects, manage resources reliably, and offer predictable failure behavior.

See also: exception safety guarantees, RAII, resource management, strong exception safety, basic exception safety.