DOC: Smart Pointers Example Is Incorrect

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   #include <stdio.h>
   #define TRACE printf
   class RefCount {
       int crefs;
   public:
       RefCount(void) { crefs = 0; }
       ~RefCount() { TRACE("goodbye(%d)\n", crefs); }
       void upcount(void) { ++crefs; TRACE("up to %d\n", crefs);}
       void downcount(void)
        {
        if (--crefs == 0)
         {
         delete this;
         }
        else
         TRACE("downto %d\n", crefs);
        }
   };
   class Sample : public RefCount {
   public:
       void doSomething(void) { TRACE("Did something\n");}
   };
   template <class T> class Ptr {
       T* p;
   public:
       Ptr(T* p_) : p(p_) { p->upcount(); }
       ~Ptr(void) { p->downcount(); }
       operator T*(void) { return p; }
       T& operator*(void) { return *p; }
       T* operator->(void) { return p; }
       Ptr& operator=(Ptr<T> &p_)    // This is newly added
           {return operator=((T *) p_);}
       Ptr& operator=(T* p_) {
           p->downcount(); p = p_; p->upcount(); return *this;
                                     // This is corrected
       }
   };

   int main() {
       Ptr<Sample> p  = new Sample; // sample #1
       Ptr<Sample> p2 = new Sample; // sample #2
       p = p2; // #1 will have 0 crefs, so it is destroyed;
               // #2 will have 2 crefs.
       p->doSomething();
       return 0;
       // As p2 and p go out of scope, their destructors call
       // downcount. The cref variable of #2 goes to 0, so #2 is
       // destroyed
   }