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POC++ pointer container with reference counting
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copied!<p>I need a collection in which i can store heap-allocated objects having virtual functions.</p> <p>I known about <code>boost::shared_ptr</code>, <code>std::unique_ptr</code> (C++11) and <code>boost::ptr_(vector|list|map)</code>, but they doesn't solve duplicate pointer problem.</p> <p>Just to describe a problem - i have a function which accepts heap-allocated pointer and stores it for future use:</p> <pre><code>void SomeClass::add(T* ptr) { _list.push_back(ptr); } </code></pre> <p>But if i call <code>add</code> twice with same parameter <code>ptr</code> - <code>_list</code> will contain two pointers to same object and when <code>_list</code> is destructed multiple deletion of same object will occur.</p> <p>If <code>_list</code> will count pointer which he stores and uses them at deletion time then this problem will be solved and objects will not be deleted multiple times.</p> <p><strong>So the question is:</strong></p> <p>Does somebody knows some library with collections (vector,list,map in essence) of pointer with auto-delete on destruction and support of reference counting?</p> <p>Or maybe i can solve this problem using some other technique?</p> <p><strong>Update:</strong></p> <p>I need support of duplicate pointers. So i can't use <code>std::set</code>.</p> <p>As <a href="https://stackoverflow.com/a/8774779/809107">Kerrek SB</a> and <a href="https://stackoverflow.com/a/8774799/809107">Grizzly</a> mentioned - it is a bad idea to use raw pointers in general and suggests to use <code>std::make_shared</code> and forget about instantiation via <code>new</code>. But this is responsibility of client-side code - not the class which i designs. Even if i change <code>add</code> signature (and <code>_list</code> container of course) to</p> <pre><code>void SomeClass::add(std::shared_ptr<T> ptr) { _list.push_back(ptr); } </code></pre> <p>then somebody (who doesn't know about <code>std::make_shared</code>) still can write this:</p> <pre><code>SomeClass instance; T* ptr = new T(); instance.add(ptr); instance.add(ptr); </code></pre> <p>So this is not a full solution which i wait, but useful if you write code alone.</p> <p><strong>Update 2:</strong></p> <p>As an alternative solution i found a clonning (using generated copy constructor). I mean that i can change my <code>add</code> function like this:</p> <pre><code>template <typename R> void SomeClass::add(const R& ref) { _list.push_back(new R(ref)); } </code></pre> <p>this will allow virtual method (R - class which extends some base class (interface)) calls and disallow duplicate pointers. But this solution has an overhead for clone.</p>

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