Question about non-POD class type

[Feng Xue OS via Gcc-patches]

For an instance of a non-POD class, can I always assume that any
operation on it should be type-safe, any wrong or even trick code
to violate this is UB in C++ spec? For example, here are some ways:

 union {
    Type1  *p1;
    Type2  *p2;
};

or 

union {
    Type1 t1;
    Type2 t2;
};

or

void *p = Type1 *p1;
Type2 *p2 = p;
p2->xxx;

Feng