Re: Why multiple inheritance fails

From:
"Vijay Visana" <vijay_visana@myorganization.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Mon, 25 Jun 2007 10:33:00 -0700
Message-ID:
<#kohm70tHHA.1188@TK2MSFTNGP04.phx.gbl>
I have noticed that Adjustor thunk is being created but still it does not
work. Wonder what is the use of that adjustor thunk then

Vijay

"Vijay Visana" <vijay_visana@myorganization.com> wrote in message
news:u%23z9M20tHHA.3588@TK2MSFTNGP06.phx.gbl...

I have following multiple inheritance logic

       A
    / > B C
    \ /
      D
here A B and C are pure abstract base classe and D is derived publicly(no
virtual inheritance ) from B and C and implements all pure virtual methods
of parent classes

I am able to call A::Method from

D* pD = new D;
B* b = pD;
C*c = pD;
c->method_of_A();
b->method_of_A();

but NOW !! in following scenerio

          A
        / > / \ \
    / \ \
  B B2 C
    \ / /
     \ / /
       \ /
          \ /
            D

here A, B, B2 AND C are pure virtual classes and D is derived publicly(no
virtual inheritance ) from B, B2 and C

now here I am not able to call A::Method from

D* pD = new D;
B* b = pD;

b->method_of_A();//not compiling ambiguous call

following is example

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// why multiple inheritance of interfaces (pure ABC) work when
inheritance hiearchy is liniear but fail when it involve loop
///
class Animal

{
   public:
       virtual void walk()=0;
};

class Cat : public Animal
{
public:
   virtual void Meo()=0;
};

class PussyCat : public Animal
{
public:
       virtual void PMeo()=0;
};

class persianCat: public PussyCat,public Cat
{
public:
   virtual void PerMeo()=0;
};

class Dog : public Animal
{
public:
   virtual void bark()=0;
};

class CatDog : public Dog,public persianCat
{
public:
   void walk()
   {
       printf("Animal Walk");
   }

void Meo()
{
   printf("meo");
}

void PMeo()
{
   printf("Pmeo");
}

void PerMeo()
{
   printf("Permeo");
}

void bark()
{
   printf("bhao bhao");
}

static CatDog* CreateInstance();
private :
   CatDog(){};
};

CatDog* CatDog::CreateInstance()
{
   return new CatDog;
}

int _tmain(int argc, _TCHAR* argv[])

{
persianCat* pPerCat = CatDog::CreateInstance();
CatDog* pCatDog = CatDog::CreateInstance();

pCatDog->walk();//Don't get error
pPerCat->walk(); //Get Error here why I don't know

delete pPerCat;
delete pCatDog;

return 0;

}

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