problem with virtual functions

[mahmoodn]

I have defined to class with virtual functions:

class A {
public:
	virtual void write( char ) = 0;
	virtual void reset() = 0;
};

class B {
public:
	virtual void read( char & ) = 0;
	virtual int num_available() = 0;
};

Then I defined another class that derived from them:

class fifo : public A, public B {
   // some functions
}

Now in the main I wrote:

fifo *afifo;
afifo = new fifo;

But I get this error:
main.cpp: In function `int main(int, char**)':
main.cpp:11: error: cannot allocate an object of type `fifo'
main.cpp:11: error: because the following virtual functions are abstract:
fifo.h:6: error: virtual void write_if::reset ()
fifo.h:12: error: virtual int read_if::num_av ailable()

What should I do?

[newb16]

You need to declare (and implement) said functions in your fifo class.

[mahmoodn]

thanks,
the functions must be defined in the fifo

class fifo : public A, public B {
public:
   ...
   void reset() {
      ....
   }
   // and others, read, write, num_avaialbe
}

[weaknessforcats]

Keep in mind that with multiple inheritance, you will have to call your own indirect base class constructors. Nornmally, your constructor onyl calls your immediate base class but with multiple inheritance this feature is disabled. Unless you call all base class constructors (direct and indirect) in the initialization list of your derived class, those constructors will not be called and you will have a garbage object.