How can you modify an object without calling member functions?

Question

At 3.10/10, the standard says:

An lvalue for an object is necessary in order to modify the object except that an rvalue of class type can also be used to

Answer 1

This seems to be accepted:

struct T {
   int x;
};

int main() {
   T().x = 3;
}

I am slightly surprised that this works, because IIRC the LHS of op= must be an lvalue, yet the following implies that even T().x is an rvalue:

struct T {
   int x;
};

void f(int& x) {
   x = 3;
}

int main() {
   f(T().x);
}

Edit: As of 4.6, GCC does warn about T().x = 3: error: using temporary as lvalue.

I can't think of any other way to modify a class object other than through data member access or member function calls. So, I'm going to say... you can't.