Question

According to C++03 Standard (23.1/3) only copy-constructible class objects can be stored in STL containers. Copy-constructible is described in 20.1.3 and requires that “&” yields address of the object.

Now suppose I have this class:

class Class {
public:
   Class* operator&()
   {
       //do some logging
       return this;
   }
   const Class* operator&() const
   {
       //do some logging
       return this;
   }
   //whatever else - assume it doesn't violate requierements
};

Can this class objects be legally stored in STL containers?

Answer 1

Yes. In C++03, the CopyConstructible requirements for &, given values t of type T and u of type const T, are:

• &t has type T*, and gives the address of t, and
• &u has type const T*, and gives the address of u.

Your overloaded operators have this behaviour; so, assuming the class meets the other CopyConstructible and Assignable requirements, values of this type can be stored in any C++03 container.

C++11 relaxes these requirements, requiring that types be movable or copyable only in containers or operations that specifically have such requirements, and removing the rather odd specification of what & must do; so your class is still fine, again assuming it meets all the other requirements for the particular container and set of operations you use.