first time:
/ * * Conclusion: * The data of the class object can be cut (SLICE), but does not affect the virtual table (Virtual Table). * Saves the pointer of the virtual table in the data area of the class object, and the responsibilities of the class object are only. * / # Include
Using namespace std;
Class a {public: void print () {cout << "this is a." <
}
}
Class B: Public a {public: void print () {cout << "this is b."
}
}
Class va {public: Virtual void print () {cout << "this is a."
}
}
Class VB: PUBLIC VA {public: void print () {cout << "this is b."
}
}
INT main (void) {a _a; b_b; a * _pa = & _A; // Pointer to the _a object.
/ / Pointer to a pointer to the _b object, but the data size accessed is SIZEOF (a) a * _PB = & _b;
VA _VA; VB _VB; VA * _VPA = & _VA;
// Pointer to a pointer to the _vb object, but the data size accessed is SIZEOF (VA) VA * _VPB = & _vb;
_PA-> Print (); _PB-> print ();
_VPA-> Print (); _vpb-> print ();
Return 0;}
The second article:
#include
Using namespace std;
Class a {public: Virtual void fun () {cout << "A :: fun" <
Virtual void fun2 () {cout << "A :: fun2" <
}
Class B: Public a {public: void fun () {cout << "b :: fun" <
Void fun2 () {cout << "b :: fun2" <
}
INT main (void) {void (); // Defines function pointer A * p = new B within a class A;
// Returns should be the index value of Slot in a VTBL, actual and A, B have no relationship fun = & a :: fun; (p -> * fun) (); // Compiler internal calculation: P -> (VPTR index) (); / * * Note: At this point P pointing to a class A object, but VTBL is the function pointer of class B.
* Or the above old saying, class object (data) only maintains VPTR, as for function addresses, run
* Calculated according to Index. * / Fun = & a :: fun2; (p -> * fun) (); delete p;
Return 0;}
Third article:
DELETE P; Compiler Maintains recycling SIZEOF (B) size in internal state, not SIZEOF (A).
If there is something wrong, please high-handed ax.
