Do I need to explicitly call the base virtual destructor

Question

When overriding a class in C    with a virtual destructor  I am implementing the destructor again as virtual on the inheriting class  but do I need to call the base destructor   If so I imagine it s something like this     MyChildClass   MyChildClass      virtual in header          Call to base destructor        this- gt MyBaseClass   MyBaseClass            Some destructing specific to MyChildClass     Am I right

User · Accepted Answer

No  destructors are called automatically in the reverse order of construction   Base classes last    Do not call base class destructors

User · Answer

Destructors in C   automatically gets called in the order of their constructions  Derived then Base  only when the Base class destructor is declared virtual   If not  then only the base class destructor is invoked at the time of object deletion   Example  Without virtual Destructor   include  lt iostream gt   using namespace std   class Base  public    Base        cout  lt  lt   Base Constructor  n           Base        cout  lt  lt   Base Destructor  n            class Derived  public Base  public    int  n    Derived        cout  lt  lt   Derived Constructor  n       n   new int 10          void display        cout lt  lt   Value    lt  lt   n  lt  lt  endl          Derived        cout  lt  lt   Derived Destructor  n           int main       Base  obj   new Derived       Derived object with base pointer  delete obj       Deleting object  return 0       Output  Base Constructor Derived Constructor Base Destructor   Example  With Base virtual Destructor   include  lt iostream gt   using namespace std   class Base  public    Base        cout  lt  lt   Base Constructor  n            virtual destructor   virtual  Base        cout  lt  lt   Base Destructor  n            class Derived  public Base  public    int  n    Derived        cout  lt  lt   Derived Constructor  n       n   new int 10          void display        cout lt  lt   Value    lt  lt   n  lt  lt  endl          Derived        cout  lt  lt   Derived Destructor  n       delete n      deleting the memory used by pointer         int main       Base  obj   new Derived       Derived object with base pointer  delete obj       Deleting object  return 0       Output  Base Constructor Derived Constructor Derived Destructor Base Destructor   It is recommended to declare base class destructor as virtual otherwise  it causes undefined behavior   Reference  Virtual Destructor

User · Answer

No  you never call the base class destructor  it is always called automatically like others have pointed out but here is proof of concept with results   class base   public      base      cout  lt  lt    FUNCTION    lt  lt  endl         base     cout  lt  lt    FUNCTION    lt  lt  endl        class derived   public base   public      derived     cout  lt  lt    FUNCTION    lt  lt  endl         derived     cout  lt  lt    FUNCTION    lt  lt  endl       adding call to base   base   here results in double call to base destructor      int main         cout  lt  lt   case 1  declared as local variable on stack   lt  lt  endl  lt  lt  endl                derived d1             cout  lt  lt  endl  lt  lt  endl       cout  lt  lt   case 2  created using new  assigned to derive class   lt  lt  endl  lt  lt  endl      derived   d2   new derived      delete d2       cout  lt  lt  endl  lt  lt  endl       cout  lt  lt   case 3  created with new  assigned to base class   lt  lt  endl  lt  lt  endl      base   d3   new derived      delete d3       cout  lt  lt  endl       return 0      The output is   case 1  declared as local variable on stack  base  base derived  derived derived   derived base   base   case 2  created using new  assigned to derive class  base  base derived  derived derived   derived base   base   case 3  created with new  assigned to base class  base  base derived  derived base   base  Press any key to continue         If you set the base class destructor as virtual which one should  then case 3 results would be same as case 1  amp  2

User · Answer

No  It s automatically called

User · Answer

No   Unlike other virtual methods  where you would explicitly call the Base method from the Derived to  chain  the call  the compiler generates code to call the destructors in the reverse order in which their constructors were called

User · Answer

No you don t need to call the base destructor  a base destructor is always called for you by the derived destructor    Please see my related answer here for order of destruction    To understand why you want a virtual destructor in the base class  please see the code below   class B   public      virtual  B                 cout lt  lt  B destructor  lt  lt endl             class D   public B   public      virtual  D                 cout lt  lt  D destructor  lt  lt endl             When you do   B  pD   new D    delete pD    Then if you did not have a virtual destructor in B  only  B   would be called   But since you have a virtual destructor  first  D   will be called  then  B

User · Answer

What the others said  but also note that you do not have to declare the destructor virtual in the derived class  Once you declare a destructor virtual  as you do in the base class  all derived destructors will be virtual whether you declare them so or not  In other words   struct A      virtual  A          struct B   public A      virtual  B           this is virtual     struct C   public A       C                  this is virtual too

[c++] Do I need to explicitly call the base virtual destructor?

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