Accessing functions through virtual tables in C++

I have two classes B and D

class B{
public:
  virtual int prva()=0;
  virtual int druga(int)=0;
};

class D: public B{
public:
  virtual int prva(){return 42;}
  virtual int druga(int x){return prva()+x;}
};

My task is to create a function that takes pointer to object B nad prints returning values of methods 'prva' and 'druga' without using their name (accessing through virtual table)

I wrote the following code that successfully prints the returning value of method 'prva', but then fails to do the same for the second method 'druga'

typedef int (*PTRFUN1)(void);
typedef int (*PTRFUN2)(int);

void function (B* var){
    int* vptr =  *(int**)var;
    PTRFUN1 fun1 = (PTRFUN1)vptr[0];
    PTRFUN2 fun2 = (PTRFUN2)vptr[1];
    pprintf("Prva:%d\n", fun1());
    printf("Druga:%d\n", fun2(2));
}

int main(void){
    B *pb = new D();
    function(pb);
}

This code executes printing: "Prva:42"

It fails to call prva() inside of 'druga' and I can't figure out why.

Additionally, if I simply remove call of prva() and let the body just be return x, the method 'druga' will always return "42" or whatever number i let 'prva' return no matter what argument I try to send through fun2()

Any ides what am I doing wrong here, and how should I access methods?

It is not possible to access the virtual table in standard C++. In fact, the language doesn't even have a concept of what a virtual table is. Virtual table is a specific (and popular) way to implement dynamic dispatch.

Any ides what am I doing wrong here

When you indirect through vptr, the behaviour of the program is undefined.

Some implementations may have way to access the table in C++, but there is no standard way. If your compiler does not, then only way is to study how the compiler implements it, the write the program to access it in assembly.