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    <p>Fact 1: The expression <code>&amp;Type::member</code> has type <code>MemberType ClassType::*</code>, where <code>ClassType</code> is the class where <code>member</code> is declared, not necessarily <code>Type</code>.</p> <p>Fact 2: It is legal (though not always safe) to <code>static_cast</code> a reference or pointer from a base class to a derived class only if the base class is not a virtual base (nor an ambiguous base). It seems to me that this is exactly the things you want to check at every use of <code>GetObjectFromMember</code>.</p> <p>So how about:</p> <pre><code>// Precondition: mptr points at the specified member of a ClassType object. // Precondition: member must not be in a virtual base class of ClassType. // // The second precondition is not an issue if the template arguments are // deduced from an &amp;AnyClass::member expression, since ClassType will // deduce as the member's actual enclosing class. template&lt;typename ClassType, typename MemberType&gt; ClassType* ObjectContainingMember(MemberType ClassType::*member, MemberType *mptr) { ClassType* dummy = 0; std::size_t member_offset = reinterpret_cast&lt;char*&gt;(&amp;(dummy-&gt;*member)) - reinterpret_cast&lt;char*&gt;(dummy); char* obj_addr = reinterpret_cast&lt;char*&gt;(mptr) - member_offset; return reinterpret_cast&lt;ClassType*&gt;(obj_addr); } // Precondition: MemberPointer points at the specified member of // an ObjectType object. Returns a pointer to that ObjectType. #define GetObjectFromMember(ObjectType,MemberName,MemberPointer) \ static_cast&lt;ObjectType*&gt;(ObjectContainingMember( \ &amp;ObjectType::MemberName, MemberPointer)) </code></pre> <p>Because of fact 1, the template parameter <code>ClassType</code> will be deduced as the class where the member is declared.</p>
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    1. COThis looks like what I need, except most of my compilers don't support decltype yet. Still it seems like the right solution for those compilers that do. Let me investigate alternatives similar to this and I'll get back to you.
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    2. COThis was definitely workable. I ended up doing template type inference instead of decltype: template< typename RequiredType, typename MemberType, typename BaseType> inline typename RequiredType *memberStaticCastTo( MemberType BaseType::*memberPointer, MemberType *memberInstance )
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    3. COYeah, I was just working out how to do it in C++03, and it's actually looking simpler than what I posted.
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