20.3 Afternotes

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Smart pointer templates are probably the second-most obvious application of templates after container templates; however, the details are far from obvious, as this chapter illustrates. Indeed, many authors cover the topic in some detail. Good material supplementing our discussion can be found in [MeyersMoreEffective], which offers a more basic discussion, and in [AlexandrescuDesign], which describes a complete, policy-based design of a family of smart pointers.

The C++ standard library contains a smart pointer template auto_ptr . It is intended for the same use as our Holder / Trule pair of templates, but avoids the use of a second template by exploiting a controversial piece of the C++ overloading rules in the context of variable initialization. ^[5]

^[5] An explanation of the mechanisms involved is well beyond the scope of this text (and not really related to templates). The controversy arises because one of the mechanisms on which auto_ptr relies is considered by some to be a defect in the C++ standard. See [JosuttisAutoPtr] for additional discussion on this topic.

Other smart pointers were proposed for inclusion in the C++ standard library, but the C++ standardization committee decided not to support them.

The Boost project offers a library containing a variety of smart pointer classes to meet a variety of needs (see [BoostSmartPtr]).

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