#include <cstdio>
#include <cstdarg>
using namespace std;

class Base
{
public:
    Base(int a) : _a(a)
    {
    }

    int Foo(int offset)
    {
        return offset + _a * _a;
    }
private:
    int _a;
};

void *DisMember(size_t size, ...)
{
    // the pointer can be more complicated than a plain data pointer
    // think of virtual member functions, multiple inheritance, etc
    if (size < sizeof(void *)) return NULL;
    va_list args;
    va_start(args, size);
    void *res = va_arg(args, void *);
    va_end(args);
    return res;
}

int main()
{
    Base b(5);
    Base c(8);

    // regular pointer to member function
    int (Base::*ptrFoo)(int);
    ptrFoo = &Base::Foo;

    printf("Calling Base::Foo(3) through the regular pointer gives %d.\n", (b.*ptrFoo)(3));

    // void *pVoid1 = reinterpret_cast<void *>(ptrFoo);    // won't work
    // void *pVoid2 = reinterpret_cast<void *>(&(b.*ptrFoo));    // won't work
    printf("sizeof(&Base::Foo) = %ld.\n", sizeof(&Base::Foo));
    void *pVoid3 = DisMember(sizeof(&Base::Foo), &Base::Foo);
    printf("%p.\n", pVoid3);

    printf("Calling Foo from the void* through b: %d.\n", reinterpret_cast<int (*)(Base *, int)>(pVoid3)(&b, 3));
    // printf("Calling Foo from the void* through c: %d.\n", reinterpret_cast<int (Base::*)(int)>(pVoid3)(3)); // won't work; gotta stick with the illegal form from above
    printf("Calling Foo from the void* through c: %d.\n", reinterpret_cast<int (*)(Base *, int)>(pVoid3)(&c, 3));
    return 0;
}