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From: Beman Dawes (beman_at_[hidden])
Date: 2000-07-14 06:52:08

Kevlin Henney wrote:

> ...
>> >Also: 'unowned'.
>>Hum... Is it still a smart pointer? Could you explain a bit?
>Yup. Going back to square one (or should that be zero as it's C++?)
>smart pointers are proxy objects that add management and access control
>to a level of indirection, idiomatically appearing to support parts of
>the built-in pointer protocol. A common application (and misconception)
>is SPs for memory management. This is only one role that they can play:
>checking, locking, loading, navigation, etc are others. Hence, most
>iterators in the standard library are examples of smart pointers even
>though they have no strong ownership semantics.

More thoughts on the above:

There is a distinction between a feature model as a software engineering
tool, and using a feature model to create a formal classification or

C&E propose feature models as software engineering tools to aid in the
design of deliverable software. Thus the boost feature model for smart
pointers would probably not include iterators since (I'm assuming, possibly
incorrectly) the boost smart pointer generator will not generate something
you would call an iterator. That would be true regardless of whether boost
uses just template magic for generation, or also uses an HTML or other
wizard. If it turns out that 100% of the boost smart pointers
configurations are memory management smart pointers, maybe we should rename
the concept memory-management-smart-pointer or similar, or at least make
that clear in the docs.

What you are in effect saying, I think, is that the same feature model
approach could also be used to create formal classifications. There the
aim is better understanding, explanation, and communication rather than
actual working code.

But for the boost SP feature model, we should only include the feature if
some real configurations will include it, even if only in version 2. That
might well apply to user-supplied-locking or
pointer-isnt-already-owned-checking, for example. But iterators or other
navigation smart pointers may be outside the scope, and if so wouldn't be


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