How to make boost::make_shared a friend of my class

Question

I have written a class with protected constructor, so that new instances can only be produced with a static create() function which returns shared_ptr\'s to my class. To provide

Answer 1

Below are some macros I wrote up to do this for you. In your case, you would use:

BOOST_MAKE_SHARED_2ARG_CONSTRUCTOR(Connection, const ConnectionManagerPtr&, const std::string&);

Macro definitions:

// Required includes
#include 
#include 
#include  

// Helper macro
#define CONST_REFERENCE(T) boost::add_reference::type>::type

/** BOOST_MAKE_SHARED_nARG_CONSTRUCTOR(CLASS_NAME, ARG1_TYPE, ARG2_TYPE, ...) 
  *
  * Use this macro inside the body of a class to declare that boost::make_shared
  * should be considered a friend function when used in conjunction with the
  * constructor that takes the given argument types.  This allows the constructor 
  * to be declared private (making it impossible to accidentally create an instance 
  * of the object without immediatly storing it in a boost::shared_ptr).  
  * Example usage:
  *
  * class Foo {
  *   private:
  *     Foo(int size, const char* name);
  *     MAKE_SHARED_2ARG_CONSTRUCTOR(Foo, int, const char*);
  * };
  * 
  * boost::shared_ptr myFoo = boost::make_shared(3, "Bob");
  *
  * Note that you need to explicitly specify the number of arguments 
  * that the constructor takes as part of the macro name.  Also, note that 
  * macros don't mix well with templated types that contain commas -- so 
  * if you have such a type, then you should typedef it to a shorter name 
  * before using it with this macro.
  */
#define BOOST_MAKE_SHARED_0ARG_CONSTRUCTOR(CLASS_NAME) \
    friend boost::shared_ptr boost::make_shared()
#define BOOST_MAKE_SHARED_1ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1))
#define BOOST_MAKE_SHARED_2ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2))
#define BOOST_MAKE_SHARED_3ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3))
#define BOOST_MAKE_SHARED_4ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3, ARG_TYPE4) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3), CONST_REFERENCE(ARG_TYPE4))
#define BOOST_MAKE_SHARED_5ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3, ARG_TYPE4, ARG_TYPE5) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3), CONST_REFERENCE(ARG_TYPE4), CONST_REFERENCE(ARG_TYPE5))
#define BOOST_MAKE_SHARED_6ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3, ARG_TYPE4, ARG_TYPE5, ARG_TYPE6) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3), CONST_REFERENCE(ARG_TYPE4), CONST_REFERENCE(ARG_TYPE5), CONST_REFERENCE(ARG_TYPE6))
#define BOOST_MAKE_SHARED_7ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3, ARG_TYPE4, ARG_TYPE5, ARG_TYPE6, ARG_TYPE7) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3), CONST_REFERENCE(ARG_TYPE4), CONST_REFERENCE(ARG_TYPE5), CONST_REFERENCE(ARG_TYPE6)), CONST_REFERENCE(ARG_TYPE7))
#define BOOST_MAKE_SHARED_8ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3, ARG_TYPE4, ARG_TYPE5, ARG_TYPE6, ARG_TYPE7, ARG_TYPE8) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3), CONST_REFERENCE(ARG_TYPE4), CONST_REFERENCE(ARG_TYPE5), CONST_REFERENCE(ARG_TYPE6)), CONST_REFERENCE(ARG_TYPE7)), CONST_REFERENCE(ARG_TYPE8))
#define BOOST_MAKE_SHARED_9ARG_CONSTRUCTOR(CLASS_NAME, ARG_TYPE1, ARG_TYPE2, ARG_TYPE3, ARG_TYPE4, ARG_TYPE5, ARG_TYPE6, ARG_TYPE7, ARG_TYPE8, ARG_TYPE9) \
    friend boost::shared_ptr boost::make_shared(CONST_REFERENCE(ARG_TYPE1), CONST_REFERENCE(ARG_TYPE2), CONST_REFERENCE(ARG_TYPE3), CONST_REFERENCE(ARG_TYPE4), CONST_REFERENCE(ARG_TYPE5), CONST_REFERENCE(ARG_TYPE6)), CONST_REFERENCE(ARG_TYPE7)), CONST_REFERENCE(ARG_TYPE8)), CONST_REFERENCE(ARG_TYPE9))