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

Just a summary of how a complete version may look like:

#include 
#include 

class Foo {
  explicit Foo(int x) {
    std::cout << "Foo::Foo(" << x << ")\n";
  }
public:
  friend boost::shared_ptr boost::make_shared(const int& x);

  static boost::shared_ptr create(int x) {
    return boost::make_shared(x);
  }

  ~Foo() {
    std::cout << "Foo::~Foo()\n";
  }
};

int main(int argc, const char *argv[]) {
  Foo::create(42);
}