Putting 'noexcept' on possible UB

struct A {
  int* a_ptr;
};

struct B {
  A* b_ptr;
};


struct C {  // iterator
  B* c_ptr;

  //...

  int& f() noexcept(?) {  // provides some access if 'C' is valid
    return c_ptr->b_ptr->a_ptr;
  }
};

Imagine: C is some custom iterator, which is always valid until its container is deleted. Otherwise, calling C::f will result in UB. We trust the user that he will never try to create C, to delete its container and then to call C::f (we will warn him that it is a bad practice).

So, the question is whether I can put noexcept(true) on f or not from the code-writing-ethics point of view? I am looking for some reasoning for any of the decisions.

C++ is built on the assumption that undefined behavior will never occur

There are no degrees of undefined behavior

noexcept is about exceptions that your code throws, with throw my_exception

So, if a function never throws exceptions it is appropriate to put on noexcept(true) even if it can invoke UB under incorrect usage.

However... (check commentaries)