Does the value of std::list<T>::end() change after modifying list?

Question

I'm trying to make use of the fact that iterators to lists remain valid after insertions and removals (except iterators to what you just removed). Is this also true of std::list<T>::end();

Suppose I try the following:

typedef std::list<int> list_int;

list_int myList;
list_int::iterator iter = myList.end();

myList.push_back(1);
myList.push_back(2);
myList.push_back(3);

if(iter == myList.end()) {
    /* do things here */
} else {
    /* do different things here */
    /* I don't expect this branch to ever execute */
}

This is important because elsewhere I might store a collection of iterators into this list, and I would test for validity by comparing against myList.end(). It's important that invalid iterators remain so even after insertions and removals.

Answer 1

The value of std::lists end iterator never changes during the lifetime of the list. It is always valid, always the same and always corresponds to the imaginary "past the end" element of the list. This means that the value of some_list.end() memorized at any point in the list's lifetime will always be the same as the value of some_list.end() at any other point of its lifetime.

The language specification doesn't state it explicitly. However, there's simply no valid operation on the list that would invalidate the end iterator or associate its value with some other location.

In your example the second branch of that if will never execute.

If I'm not missing anything, the same is true for std::map and std::set as well.