固定对象在堆或者栈上分配（还没有实验过）

相信一些朋友也碰见过这样的面试题目,本文尝试着给出解答.

1. 分配对象在堆上

　　那么,必然要禁止对象在栈上面分配.一个很简单的办法,就是构造函数私有化(提供额外的接口生成对象),那么在栈上面就不可以分配.可是我们还需要这个对象要被析构,那么可以提供一个接口,显式的释放掉这个接口,也就是说delete也得给他禁掉~~~

　　考虑另外一个问题,C++有placement new,我自己new一块内存,然后在你这上面构造.问题就变得很恶心,看来我们只有把new,delete都给他禁掉...

　　好了,我们现在知道该怎么做:

• createInstance()接口产生对象
• dispose()接口销毁对象
• new/delete操作符全部不可见

来看我们的代码:

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class  HeapObject{ public :      static  HeapObject* createInstance()      {          return  new  HeapObject;      }      void  dispose()      {          delete  this ;      } protected :      HeapObject(){}      ~HeapObject(){}        static  void * operator new  (std:: size_t  size) throw  (std::bad_alloc)      {          return  ::operator new (size);      }      static  void * operator new  (std:: size_t  size, const  std::nothrow_t& nothrow_constant) throw ();      static  void * operator new  (std:: size_t  size, void * ptr) throw ();      static  void * operator new [] (std:: size_t  size) throw  (std::bad_alloc);      static  void * operator new [] (std:: size_t  size, const  std::nothrow_t& nothrow_constant) throw ();      static  void * operator new [] (std:: size_t  size, void * ptr) throw ();        static  void  operator delete  ( void * ptr) throw  ()      {          ::operator delete (ptr);      }      static  void  operator delete  ( void * ptr, const  std::nothrow_t& nothrow_constant) throw ();      static  void  operator delete  ( void * ptr, void * voidptr2) throw ();        static  void  operator delete [] ( void * ptr) throw  ();      static  void  operator delete [] ( void * ptr, const  std::nothrow_t& nothrow_constant) throw ();      static  void  operator delete [] ( void * ptr, void * voidptr2) throw (); };

2. 分配对象在栈上

　　只能分配对象在栈上面,那么new显然是不能用的,否则就是在堆上面分配对象了,理所当然,delete也得禁掉.

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class  StackObject { public :      StackObject(){}      ~StackObject(){} protected :      static  void * operator new  (std:: size_t  size) throw  (std::bad_alloc);      static  void * operator new  (std:: size_t  size, const  std::nothrow_t& nothrow_constant) throw ();      static  void * operator new  (std:: size_t  size, void * ptr) throw ();      static  void * operator new [] (std:: size_t  size) throw  (std::bad_alloc);      static  void * operator new [] (std:: size_t  size, const  std::nothrow_t& nothrow_constant) throw ();      static  void * operator new [] (std:: size_t  size, void * ptr) throw ();        static  void  operator delete  ( void * ptr) throw  ();      static  void  operator delete  ( void * ptr, const  std::nothrow_t& nothrow_constant) throw ();      static  void  operator delete  ( void * ptr, void * voidptr2) throw ();        static  void  operator delete [] ( void * ptr) throw  ();      static  void  operator delete [] ( void * ptr, const  std::nothrow_t& nothrow_constant) throw ();      static  void  operator delete [] ( void * ptr, void * voidptr2) throw (); };