d42d311a   
   From: francis.glassborow@btinternet.com   
      
   On 25/08/2011 14:57, Goran wrote:   
   > On Aug 25, 1:44 am, linq936  wrote:   
   >> Hi,   
   >> The question just came to me and could not find an answer.   
   >>   
   >> Normally we do not declare constructor and destructor in pure class   
   >> and compiler generates them, but since the class is pure, compiler   
   >> should declare the destructor as virtual, isn't it?   
   >   
   > No. Counter example: I often use pure virtual classes to often   
   > "interfaces", Java-style. In this case, destructor that is called is   
   > coming from another part of inheritance tree and virtual destructor in   
   > pure virtual base isn't needed.   
   >   
   >   
   >> class D {   
   >>     public:   
   >>        virtual void do_sth() {}   
   >>   
   >>      ... some other things ...   
   >>   
   >> };   
   >>   
   >> int main()   
   >> {   
   >>    Base* p = new D();   
   >>    p->do_sth();   
   >>    delete p;   
   >>    return 0;   
   >>   
   >> }   
   >   
   > Here, you have a possible bug: you have a pointer to base, and when   
   > you call delete, compiler will call destructor. But it will not do it   
   > virtually because Base has none (even if you add one to Derived).   
      
   Of course Base has a dtor, just because the programmer has not written   
   it does not mean there isn't one. I think the OP is wondering about   
   whether the computer generated dtor should not be virtual. I know we   
   have discussed this many times over the last two decades and some people   
   have good reasons why this is not the case.   
      
   In C++11 you can write (in the base class))   
      virtual ~Base = default;   
      
   and the compiler will generate the dtor for Base just as it would if you   
   had said nothing, except that the dtor is now virtual.   
      
      
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