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copied!<p>The code fails to compile for some obvious reasons. Most of the <code>typenameS</code> are unnecessary. I suppose <code>nullptr</code> is some homebrew <code>#define</code> (It is not the C++11 <code>nullptr</code> for sure).</p> <p>Here is a prettified, compiling version that makes it easier to see what is actually going on:</p> <pre><code>#include <iostream> template<class C, class M> inline C* get_parent_this(M C::*member_ptr, M* const member_this) { C* base = NULL; // !!! this is the tricky bit !!! char* member = reinterpret_cast<char*>(&(base->*member_ptr)); return reinterpret_cast<C*>(reinterpret_cast<char*>(member_this) - member ); } class Owner { int x, pr_y; virtual int get_y() {return pr_y;} void set_y(int v) {pr_y = v;} public: struct { operator int() { return get_parent_this(&Owner::y, this)->get_y(); } void operator =(int v) { get_parent_this(&Owner::y, this)->set_y(v); } } y; }; </code></pre> <p>The tricky bit: This involves the dereference of a null-pointer. This is somewhat equal to the way the macro <code>offsetof</code> in <code>stddef.h</code> used to be (and still is) defined in some compilers. This works reliably on some compilers but is undefined behavior. Here are a few links to discussions about the topic:</p> <ul> <li><a href="https://stackoverflow.com/questions/7511211/address-of-null-pointer/7511337#7511337">Address of Null pointer?</a></li> <li><a href="http://en.wikipedia.org/wiki/Offsetof" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Offsetof</a></li> </ul> <p>I don't think it is worth repeating the discussion here. I really don't see what the code is buying you, besides obfuscated public data. For the few cases where you really need a <code>setter</code> I would just write it instead of using this. If your coding style prohibits public data for idiosyncratic reasons, write a set of macros to define them.</p>

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