7.15 Summary

Congratulations! You have just read one of the longest, wildest chapters of this book—an effort that we hope has paid off. Now you know a lot of things about smart pointers and are equipped with a pretty comprehensive and configurable SmartPtr class template.

Smart pointers imitate built-in pointers in syntax and semantics. In addition, they perform a host of tasks that built-in pointers cannot. These tasks might include ownership management and checking against invalid values.

Smart pointer concepts go beyond actual pointer behavior; they can be generalized into smart resources, such as monikers (handles that don't have pointer syntax, yet resemble pointer behavior in the way they enable resource access).

Because they nicely automate things that are very hard to manage by hand, smart pointers are an essential ingredient of successful, robust applications. As small as they are, they can make the difference between a successful project and a failure—or, more often, between a correct program and one that leaks resources like a sieve.

That's why a smart pointer implementer should invest as much attention and effort in this task as possible; the investment is likely to pay in the long term. Similarly, smart pointer users should understand the conventions that smart pointers establish and use them in accordance with those conventions.

The presented implementation of smart pointers focuses on decomposing the areas of functionality into independent policies that the main class template SmartPtr mixes and matches. This is possible because each policy implements a well-defined interface.