Item 9. Writing Exception-Safe Code桺art 2

Difficulty: 8

Now that we have the default constructor and the destructor under our belts, we might be tempted to think that all the other functions will be about the same. Well, writing exception-safe and exception-neutral copy and assignment code presents its own challenges, as we shall now see.

Consider again Cargill's Stack template:

template <class T> class Stack 


{


public:


  Stack();


  ~Stack();


  Stack(const Stack&);


  Stack& operator=(const Stack&);


  /*...*/


private:


  T*     v_;      // ptr to a memory area big


  size_t vsize_;  //  enough for 'vsize_' T's


  size_t vused_;  // # of T's actually in use


};

Now write the Stack copy constructor and copy assignment operator so that both are demonstrably exception-safe (work properly in the presence of exceptions) and exception-neutral (propagate all exceptions to the caller, without causing integrity problems in a Stack object).