Reallocation can occur when a member function modifies its container. Modifying member functions include reserve() and resize(), push_back(), pop_back(), erase(), clear(), insert(), and others. In addition, assignment operations and modifying algorithms can also cause reallocation. When a container reallocates its elements, their addresses change. Consequently, the values of existing iterators are invalidated Kalev 99. Using invalid iterators yields undefined results.
Non-
...
Compliant Code Example
...
In this example, the iterator pos is invalidated after the call to insert and subsequent loop iterations have undefined behavior.
...