On Fri, 21 Dec 2007 08:44:17 -0800, interec wrote:

On Dec 21, 2:34 am, Sachin <sachinc.bira...@gmail.com> wrote:

On Dec 21, 2:05 pm,

I have trying to set up a three level inheritance heirarchy (see
files test.h/cpp below). When I compile this code using g++, I get
the following errors:

bash-3.00$ g++ test.cpp
test.cpp: In constructor `Lev2::Lev2(int, int, int)': test.cpp:33:
error: no matching function for call to `Lev0::Lev0(const void**)'
test.h:27: note: candidates are: Lev0::Lev0(const Lev0&) test.cpp:6:
note: =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Lev0::Lev0(int)

Can someone please explain whats going on and how I can fix this
problem. Please see code below. If I remove the classes ILev2 and
Lev2 everything compiles fine. Thanks

//-------------------------- FILE: test.h
--------------------------//

#include <iostream>
#include <iomanip>

class ILev0
{
=A0public:
=A0 virtual ~ILev0() {}
=A0 virtual void PrintLev0() =3D 0;

};

class ILev1: public virtual ILev0
{
=A0public:
=A0 virtual ~ILev1() {}
=A0 virtual void PrintLev1() =3D 0;

};

class ILev2: public virtual ILev1
{
=A0public:
=A0 virtual ~ILev2() {}
=A0 virtual void PrintLev2() =3D 0;

};

class Lev0: public virtual ILev0
{
=A0public:
=A0 Lev0(int nNum);
=A0 virtual void PrintLev0();

=A0protected:
=A0 int m_nNum0;

};

class Lev1: public virtual Lev0, public virtual ILev1 {
=A0public:
=A0 Lev1(int nNum0, int nNum1);
=A0 virtual void PrintLev1();
=A0protected:
=A0 int m_nNum1;

};

class Lev2: public virtual Lev1, public virtual ILev2 {
=A0public:
=A0 Lev2(int nNum0, int nNum1, int nNum2); virtual void PrintLev2();
=A0protected:
=A0 int m_nNum2;

};

//-------------------------- FILE: test.cpp
------------------------// #include "test.h"

//-------

Lev0::Lev0(int nNum)
=A0 :m_nNum0(nNum)
{

}

void Lev0::PrintLev0()
{
=A0 std::cout << "Lev0 Num: " << m_nNum0 << std::endl;

}

//-------

Lev1::Lev1(int nNum0, int nNum1)
=A0 :Lev0(nNum0),
=A0 =A0m_nNum1(nNum1)
{

}

void Lev1::PrintLev1()
{
=A0 std::cout << "Lev1 Num: " << m_nNum0 << ", " << m_nNum1 <<
std::endl;

}

//-------

Lev2::Lev2(int nNum0, int nNum1, int nNum2)
=A0 :Lev1(nNum0, nNum1),
=A0 =A0m_nNum2(nNum2)
{

}

void Lev2::PrintLev2()
{
=A0 std::cout << "Lev2 Num: " << m_nNum0 << ", " << m_nNum1 << ", " <=

m_nNum2 << std::endl;

}

//---

main()
{
=A0 Lev0 *b =3D new Lev0(10);
=A0 b->PrintLev0();

}

//------------------------------------------------------------------//

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Call to Constructor of Lev0 class is missing in the Lev2 constructor.
Resolution is to either implement default constructor in Lev0 class or
make a call to Lev0 constructor in the constructor of Lev2 as follows:
Lev2::Lev2(int nNum0, int nNum1, int nNum2)
=A0 :Lev1(nNum0, nNum1),Lev0(nNum0),
=A0 =A0m_nNum2(nNum2)
{

}

Lev2 constructor explicitly calls Lev1 constructor and Lev1 constructor
explicitly calls Lev0 constructor so why do I need to add a call to Lev0=
constructor in Lev2 ?

Because it's a virtual base class.

--
Tadeusz B. Kopec (tko...@NOSPAMPLEASElife.pl)
Enzymes are things invented by biologists that explain things which
otherwise require harder thinking.
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 -- Jerome Lettvin- Hide quoted text -

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