对象生成问题求解

class   sam  
  {  
  protected:  
      ~sam()   {}  
  public:  
      sam()   :   i(0)  
      {}  
   
      int   i;  
  };  
   
  sam   s;     //   error  
   
  sam*   ps   =   new   sam;   //   ok  
   
  why   compiler   complain   about   the   first   statement?  
   
  Thanks   in   advance  
  问题点数：20、回复次数：3Top

1 楼T34（我是坦克我怕谁）回复于 2002-04-17 22:11:10 得分 12

I   think,   in   the   1st   case,   the   compiler   generate   s   on   the   stack   for   you,   and   will   call   destructor   for   you   when   the   life   of   s   is   ended.  
  suppose   you   have   the   following   code  
  void   f()  
  {  
          sam   s;  
          some   action;  
  }  
   
  the   compiler   will   translate   it   into   something   like   this  
  void   f()  
  {  
          allocate   s   on   stack  
          sam::sam(&s);  
          some   action;  
          sam::~sam()    
  }  
  so   it   complains   for   lacking   of   desctuctor.  
   
  in   the   2nd   case,   you   new   a   sam   class   object   on   heap,   so   it   is   up   to   you   to   free   it,   and   no   error   occurs,   but   of   course   delete   ps   will   not   be   safe.Top

2 楼rovoboy（魂之猎人）回复于 2002-04-17 22:12:46 得分 8

My   English   Bad.  
  May   Some   Language   Mistake.  
   
  delete   ps;  
  Will   Fail   Because   Of   The   Same   Reason   As   sam   a  
   
  sam   s;  
  Compiler   Confirms   That   You   Can   Do   sam()   &   ~sam()  
   
  sam*   ps   =   new   sam;  
  Compiler   Only   Confirms   That   You   Can   Do   sam()  
   
  delete   ps;  
  Compiler   Only   Confirms   That   You   Can   Do   ~sam()  
  Top

3 楼wlz47（秋水沉舟）回复于 2002-04-17 22:20:44 得分 0

if   use  
   
  delete   ps;       //   compile   error   hereTop

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