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POPlacement new based on template sizeof()
 

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    <p>Is this legal in c++11? Compiles with the latest intel compiler and appears to work, but I just get that feeling that it is a fluke.</p> <pre><code> class cbase { virtual void call(); }; template&lt;typename T&gt; class functor : public cbase { public: functor(T* obj, void (T::*pfunc)()) : _obj(obj), _pfunc(pfunc) {} virtual void call() { (_obj)(*_pfunc)(); } private: T&amp; _obj; void (T::*_pfunc)(); //edited: this is no good: //const static int size = sizeof(_obj) + sizeof(_pfunc); }; class signal { public: template&lt;typename T&gt; void connect(T&amp; obj, void (T::*pfunc)()) { _ptr = new (space) functor&lt;T&gt;(obj, pfunc); } private: cbase* _ptr; class _generic_object {}; typename aligned_storage&lt;sizeof(functor&lt;_generic_object&gt;), alignment_of&lt;functor&lt;_generic_object&gt;&gt;::value&gt;::type space; //edited: this is no good: //void* space[(c1&lt;_generic_object&gt;::size / sizeof(void*))]; }; </code></pre> <p>Specifically I'm wondering if <code>void* space[(c1&lt;_generic_object&gt;::size / sizeof(void*))];</code> is really going to give the correct size for c1's member objects (_obj and _pfunc). (It isn't).</p> <p>EDIT: So after some more research it would seem that the following would be (more?) correct:</p> <pre><code>typename aligned_storage&lt;sizeof(c1&lt;_generic_object&gt;), alignment_of&lt;c1&lt;_generic_object&gt;&gt;::value&gt;::type space; </code></pre> <p>However upon inspecting the generated assembly, using placement new with this space seems to inhibit the compiler from optimizing away the call to 'new' (which seemed to happen while using just regular '_ptr = new c1;'</p> <p>EDIT2: Changed the code to make intentions a little clearer.</p>
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    1. COHow is that even supposed to compile without providing an initializer for a reference member in `c1`? Is there any specific importance in that reference member or not?
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    2. COAlso, what is the idea behind calculating memory size through `sizeof(_obj)`, which evaluates to the size of full object (i.e. `sizeof T`), yet later construct a `c1<some_type_t>` object in that place, which will physically contain only a *reference* to `some_type_t` (implemented as a pointer)?
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    3. COI don't know if it compiles or not, it's a very simplified example I made to post here to cut to the relevant parts. I'm writing a signal/callback class and wish to eliminate dynamic memory allocation if possible.
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