Any real example of reinterpret_cast changing a pointer value?

Question

According to C++ Standard, a reinterpret_cast of a pointer T* to some other type pointer Q* can change or not change the pointer value dep

Answer 1

class A1 { int a1; };
class A2 { int a2; };

class B: public A1, public A2 { };

#define DBG(val)  cout << #val << ": " << val << endl

// test code
B b;
DBG(&b);                                           // prints 0x42

void *p_blank = &b;
DBG(p_blank);                                      // prints 0x42
A2 *p_a2 = &b; 
DBG(p_a2);                                         // prints 0x46
void *p_reinterpreted = reinterpret_cast(&b);
DBG(p_reinterpreted);                              // prints 0x42
A2 *p_reinterpreted2 = reinterpret_cast(&b);
DBG(p_reinterpreted2);                             // prints 0x42

A2 *p_a2 = &b means give me the pointer to an A2 object within the B object. reinterpret_cast(&b) means give me the pointer to b and treat it as an A2 pointer. The result of this reinterpret_cast has the type 'pointer to A2', therefore it produces no warning when assigned to a void* variable (or to a A2* variable).