Discussion

The basic, strong, and no-fail (then known as nothrow) guarantees were originally described in [Abrahams96] and publicized in [GotW], [Stroustrup00] §E.2, and [Sutter00] with respect to exception safety. They apply to all error handling regardless of the specific method used, and so we will use them to describe error handling safety in general. The no-fail guarantee is a strict superset of the strong guarantee, and the strong guarantee is a strict superset of the basic guarantee.

In general, every function should provide the strongest guarantee that it can provide without needlessly penalizing calling code that doesn’t need the guarantee. Where possible, it should additionally provide enough functionality to allow calling code that needs a still stronger guarantee to achieve that (see the vector::insert case in the Examples).