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Failure in sizeof() function while using Member-Function-Pointers

When using member-function-pointers I noticed that they have a size of 8Bytes each. However when I ask the compiler it says it is only 4Bytes. Having a couple of objects in you program which have member-function-pointers and are created dynamically with new will allways crash your program.

Please refer to the following source-code and documentation:

#include  <StdIO.h>
#include  <Reg164ci.h>

/*
        A simple external object
        */
class cCalculator {

        public:
                int calculate();

};

int cCalculator::calculate(){
        return 27;
}

/*
        The description of the member-function-pointer
*/
typedef int (cCalculator::*fptr)();



/*
        An object with an array of such member-function-pointers
        which is able to call these functions by an index.
*/
class cAnObject  {
public:
   cAnObject();
         ~cAnObject();

         fptr fptr_array[2];    // 2 x 8 bytes = 16 bytes (see watchwindow)

        int   member1;                  // 2 bytes
        int       member2;              // 2 bytes

                                        // --------------------------------------
                                        // total: 20bytes = 0x14bytes

};
/*
        The constructor
*/

cAnObject::cAnObject()  {
  member1 = 1;
  member1 = 2;
}

/*
        The destructor
*/
cAnObject::~cAnObject()  {
  member1 = 0;
  member1 = 0;
}

int main (void)  {

        // now we have the external object
        cCalculator calc1;
        cCalculator calc2;

        // and a couple of objects containing some function pointes
        cAnObject test1;
        cAnObject test2;
        cAnObject test3;

        fptr memberfunction = &(cCalculator::calculate);
        test1.fptr_array[0] =  memberfunction;


        // here we get the size of our objects (see watch window)
        volatile unsigned long object_addr1 = (unsigned long) &test1;
        volatile unsigned long object_addr2 = (unsigned long) &test2;
        volatile unsigned long object_sizeA = object_addr2 - object_addr1;
        volatile unsigned long object_sizeB = sizeof( test1 );
        //...

        // please notice that the static objects have a distance
        // which is different from its size ? why?
        // count the bytes and you see the sizeof() is wrong !!


        // now we simply create the dynamic object (with the wrong size), why ? compiler ?
        // which here leads to an -access violation-, due to
        // the wrong calculated size of the function pointers
        cAnObject * p_test4;
        p_test4 = new cAnObject;
        // and set the function
        p_test4->fptr_array[0] = memberfunction;

        // calc the size
        volatile unsigned long objectSize4 = sizeof(    (*p_test4)      );


        // ----
        // now the function call itself
        cCalculator * p_calc;

        // here we select our target object
        p_calc = &calc1;

        // do the static object call by an index == 0
        fptr p_fct1 = test1.fptr_array[0];
        int x = ( (p_calc)->*( p_fct1 ))( );

        // now use the other object
        p_calc = &calc2;

        // do the dynamic object call   by an index == 0
        fptr p_fct4 = p_test4->fptr_array[0];
        int y = ( (p_calc)->*( p_fct4 ))( );


        // if there is any time please notice that there is a second bug:
        //   try to remove the line "fptr p_fct4 = ..."
        //       and put it into one line like "   int y = ( (p_calc)->*( p_test4->fptr_array[0] ))( );      "
        // and your whole program will crash !

        // just print the result
        printf("%d = %d \r", x, y );

  while (1);
}