References, pointers, and iterators referring to the elements of a basic_string sequence may be invalidated
by the following uses of that basic_string object:

• As an argument to non-member functions swap(), operator>>(), and getline().
• As an argument to basic_string::swap().
• Calling data() and c_str() member functions.

• Calling non-const member functions, except {{operator\[\]()}}, {{at()}}, {{begin()}}, {{rbegin()}}, {{end()}}, and {{rend()}}.

• Subsequent to any of the above uses except the forms of {{insert()}} and {{erase()}} which return iterators, the first call to non-const member functions {{operator\[\]()}}, {{at()}}, {{begin()}}, {{rbegin()}}, {{end()}}, or {{rend()}}.

References

21.3 Class template basic_string