Interview Questions: use C to simulate the polymorphism of C ++

There are two C ++ classes:

Class base {

Public:

Base (int A, int B): M_a (A), m_ B (B ){}

Virtual void func1 ();

Virtual int func2 ();

PRIVATE:

Int M_a, m_ B;

}

Class derived: public base {

Public:

Derived (int A, int B, double D): Base (a, B), m_d (d ){}

Virtual int func2 ();

PRIVATE:

Double m_d;

}

Simulate the implementation mechanism of the C ++ compiler, use the C language to define the base and derived, and implement the Code for creating two classes.

========================================================== ======================================

Typedef void ** vtblptr; // combine the meaning

Struct base_t

{

Vtblptr _ vtbl;

Int M_a;

Int m_ B;

};

Struct derived_t

{

Vtblptr _ vtbl;

Int M_a;

Int m_ B;

Double m_d;

};

New Base

Base_t * pbase = malloc (sizeof (base_t ));

Pbase-> _ vtbl [0] = & _ base_t_func1;

Pbase-> _ vtbl [1] = & _ base_t_func2;

_ Base_t_base (pbase, a, B); // It is said that the constructor does not need this?

New derived

Derived_t * pderived = malloc (sizeof (derived_t ));

Pderived-> _ vtbl [0] = & _ base_t_func1;

Pderived-> _ vtbl [1] = & _ derived_t_func2;

Derived_t Constructor

Void _ derived_t_derived (derived_t * pderived, int A, int D)

{

_ Base_t_base (base_t *) pderived, A, B );

Pderived-> m_d = D;

};