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POReferences to boost::smart_ptr pointed to object and checking their validity
 

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  1. POReferences to boost::smart_ptr pointed to object and checking their validity
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    <p>Given the following:</p> <pre><code>class Curve { public: typedef boost::shared_ptr&lt;Curve&gt; Pointer; // ... private: // ... }; class CurveShift: public Curve { public: CurveShift(const Curve &amp; curve); // ... private: const Curve &amp; curve_; // ... }; </code></pre> <p>I was wondering whether there is a consensus best practice to use when you want to do something like:</p> <pre><code>Curve::Pointer pointer(new Curve()); SomeGlobalRepository::Add("key", pointer); </code></pre> <p>And in some other place you have:</p> <pre><code>CurveShift cs(*SomeGlobalRepository::Get("key")); </code></pre> <p>You don't really have any assurance that <code>SomeGlobalRepository</code> will contain the original <code>Curve::Pointer</code> when <code>CurveShift</code> will need it, and hence <code>curve_</code> might point to deallocated memory, or even memory that was already reallocated to something else. I believe that one possible solution would be for <code>CurveShift</code> to use a <code>boost:weak_ptr&lt;Curve&gt;</code> instead of a <code>const Curve &amp;</code>, but I am pretty certain that would mean that you can't use <code>Curve</code> on the stack anymore, and any instance would have to go on the heap (with the constructors becoming private and the objects being created through a factory). Is there a better strategy to achieve the desired behavior? My gut feeling is that while in theory this could be a serious problem, practical use cases would not lend themselves to creating these tricky situations.</p>
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    1. USildjarn
    1. USPaschover
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    1. COWhy not have `CurveShift` hold a `shared_ptr<Curve>` itself? That is sort of what the "shared" is all about...
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      1. POReferences to boost::smart_ptr pointed to object and checking their validity
      1. USNemo
    2. CODoes the network of curves contain cycles, or not? If not then everything should be `shared_ptr`. And I don't see how there sensibly can be cycles, since `CurveShift` holds a reference, so a `CurveShift` can only reference a `Curve` that was created before it. A `CurveShift` could reference itself, to create a cycle, but that doesn't seem very sensible...
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      1. POReferences to boost::smart_ptr pointed to object and checking their validity
      1. USSteve Jessop
    3. COIf the curve to be shifted is allocated on the stack, how do I get a shared_ptr to it?
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      1. POReferences to boost::smart_ptr pointed to object and checking their validity
      1. USPaschover
 

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