Conversion of UPCASET and DOWNCAST types in C ++

Example:

Class

{

Int ai;

};

Class C

{

Int ci;

};

Class B: public A, public C

{

Int bi;

};

Int _ tmain (int argc, _ TCHAR * argv [])

{

B B;

A * pa = & B;

C * pc = & B;

Return 0;

}

We can see that pa points to the address of A sub-object in B, while pc points to the address of C sub-object in B.

Let's look at the reverse situation:

In Main ()

A;

A a_tmp;

C c;

A. ai = 3;

A_tmp.ai = 4;

C. ci = 5;

B * pba = static_cast <B *> (& a); // you must use static_cast or force conversion. Otherwise, compilation fails.

B * pbc = static_cast <B *> (& c); // same

Return 0;

}

We can see that after the forced conversion, the C sub-object in pba actually points to a_tmp, so down_cast conversion is not safe.