Re: A question about multiple inheritance in C++!

From:

"Jim Langston" <tazmaster@rocketmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 22 Aug 2007 06:20:24 CST

Message-ID:

<mfQyi.124$E52.86@newsfe12.lga>

"Guofu Chen" <gchen@mathworks.com> wrote in message
news:fadj5o$73l$1@fred.mathworks.com...

Hi,In the following function:

#include <iostream>
using namespace std;

class V
{
public:
    V()
    {cout << "V()" << endl;};
    V(int)
    {cout << "V(int)" << endl;};
};

class A: virtual V
{
public:
    A(){};
    A(int){};
};

class B: virtual V
{
public:
    B(){};
    B(int){};
};

class C: public A, public B
{
public:
    C(){};
    C(int){};
};

int main()
{
    V v(1);
    A a(2);
    B b(3);
    C c(4);
    return 0;
}

The expected result is
V(int)
V(int)
V()
V()

but I compiled the code and run it on both Windows visual studio 6.0 and
GNU
g++, all I got are the same:
V(int)
V()
V()
V()

Can someone explain to me why the answer is not
V(int)
V(int)
V(int)
V(int)

Thanks!

As others have stated, you need to pass the paramter on to the constructor
of the base. The way to do this is with an initialization list. I.e.

class A: virtual V
{
public:
     A(){};
     A(int v): V( int v ){};
};

You should be able to figure out the others for yourself.

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