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POWhy doesn't shared_ptr have a virtual descructor? (and how can I get around this?)
 

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  1. POWhy doesn't shared_ptr have a virtual descructor? (and how can I get around this?)
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    <p>I wanted to make a special version of <code>shared_ptr</code> that would perform specific operations when it was created or destroyed, but my plans appear to be foiled by the realization that <code>shared_ptr</code>'s destructor is non virtual, meaning when I override it, my pointers never get cleaned up when the last instance of them are destroyed.</p> <p>The only alternative that comes to mind is to build in this behavior into every class that I want to use with my hypothetical custom <code>shared_ptr</code>, and that's not feasible (or possible in some cases). </p> <p>Edit:</p> <p>The reason I want this is because I want to use some classes as userdata objects in lua, and I want each one of my objects that I use this way to have a fenv table unique to it that will be cleaned up when all references to the object have been removed. I plan on using the address of the pointer as they key into a table that holds the fenv table.</p> <p>Lets say I have a widget that can have other widgets as children. I create two widgets in Lua, then set one as the child of the other and remove all lua references to the child widget (the fact that it's a child is handled in C++). The GC can now run at any time and remove the child. I don't necessarily want the child to have it's destructor run though, so I want to make it a shared_ptr. That way, C++ objects can still use it after Lua has cleaned it up. If I've assigned values or functions to it's fenv I still want to be able to access them. Only when the final reference to my child widget is removed do I want the fenv tabled to be removed totally.</p>
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    1. USj0k
    1. USAlex
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    1. COcan you tell us what you intend to do in the specialization of the `shared_ptr`? May be there are alternative approaches..
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      1. POWhy doesn't shared_ptr have a virtual descructor? (and how can I get around this?)
      1. USNaveen
    2. COAs usual, tell us the goal not the step. It doesn't have a virtual destructor because it's not intended to be a base class.
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      1. USGManNickG
    3. COUpdated the question with the reason I want to do this.
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      1. USAlex
 

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