Size calculation for C + + classes

CLASS&NBSP;A{};CLASS&NBSP;B{CHAR&NBSP;CH;VIRTUAL&NBSP;VOID&NBSP;FUNC0 ()   {  }};class  C{char ch1;char ch2;virtual void func ()   {  }virtual void  Func1 ()   {  }};class D : public A, public C{int d; Virtual void func ()   {  }virtual void func1 ()   {   }};CLASS&NBSP;E&NBSP;:&NBSP;PUBLIC&NBSP;B,&NBSP;PUBLIC&NBSP;C{PUBLIC:INT&NBSP;E;VIRTUAL&NBSP;VOID&NBSP;FUNC0 () &NBSP;&NBSP;{&NBSP;&NBSP;}VIRTUAL&NBSP;VOID&NBSP;FUNC1 ()   {  }//Subclass (E) does not implement Func (), So in the subclass of E, the vfptr of B points to the Func () and E's func1 () virtual void func123 () of C ()   {  }}int main () {         //result=1, empty class, size 1         cout <<  "A="  << sizeof (A)  << endl;                 //result=8,4 (vfptr,4) +4 (char ch, memory alignment, 4)  = 8        cout <<  "b="  << sizeof (B)  <<  endl;   //result=8 , 4 (vfptr,4) +4 (CHAR&NBSP;CH1,CHAR&NBSP;CH2, memory alignment, 4)  =  8  cout <<  "c="  << sizeof (C)  << endl;     //result=12, 4 (vfptr,4 of Class D) +4 (existence of base class CHAR&NBSP;CH1,CHAR&NBSP;CH2, memory Alignment, 4) +4 (int d)  = 12d obj_d; //the address of the two virtual functions in Class D is saved first in the virtual function table that vptr points to cout <<  "d="  <<  sizeof (Obj_d)  << endl;    //result=20, (multiple inheritance) inherits the number of classes with virtual functions, there are many virtual function pointers, That is, these virtual function pointers make up their own vfptr (the compiler no longer gives its own virtual function plug vfptr)//4 (b's Vfptr) +4 (char ch) +4 (Vfptr of C) +4 (c  char ch1, CHAR&NBSP;CH2) +4 (e  in int d)  = 20//This can be seen from the debug e obj_e;obj_e.e = 123;cout  <<  "E="  <&Lt; sizeof (obj_e)  << endl;             return 0;}

Size calculation for C + + classes