print the virtual function table of an object.

print_vtable.cpp

#include <cstring>
#include <iomanip>
#include <iostream>
using namespace std;

class Base1 {
  public:
    virtual void f() { cout << "Base1::f" << endl; }
    virtual void g() { cout << "Base1::g" << endl; }
    virtual void h() { cout << "Base1::h" << endl; }
};

class Base2 {
  public:
    virtual void f() { cout << "Base2::f" << endl; }
    virtual void g() { cout << "Base2::g" << endl; }
    virtual void h() { cout << "Base2::h" << endl; }
};

class Base3 {
  public:
    virtual void f() { cout << "Base3::f" << endl; }
    virtual void g() { cout << "Base3::g" << endl; }
    virtual void h() { cout << "Base3::h" << endl; }
};

class Derive : public Base1, public Base2, public Base3 {
  public:
    virtual void ff() { cout << "Derive::ff" << endl; }
    virtual void gg() { cout << "Derive::gg" << endl; }
    virtual void hh() { cout << "Derive::hh" << endl; }
};

typedef void (*Fun)(void);

void dumpmemory(void *memstart, size_t bytes) {
    unsigned char t;
    char *mem = (char *)memstart;
    size_t j = 0;
    for (size_t i = 0; i < bytes; i++) {
        memcpy(&t, mem + i, 1);
        cout.fill('0');
        cout.width(2);
        cout << hex << (int)t << ' ';
        if (++j % 8 == 0)
            cout << endl;
    }
}

int main() {

    Fun pFun = NULL;

    Derive d, e;

    Fun **pVtab = (Fun **)addressof(d);
    for (int i = 0;; i++) {
        Fun *vtable = pVtab[i];
        // dumpmemory(vtable, 256);
        cout << "virtual table " << i << ":" << endl;
        for (int j = 0;; j++) {
            Fun vfunc = vtable[j];
            if (~((int64_t)vfunc | 0xff) == 0)
                break;
            cout << (void *)vfunc << " -> ";
            vfunc();
        }
    }
    return 0;
}