23 Strings library [strings]

23.4 String classes [string.classes]

23.4.3 Class template basic_string [basic.string] General requirements [string.require]

If any operation would cause size() to exceed max_size(), that operation throws an exception object of type length_error.
If any member function or operator of basic_string throws an exception, that function or operator has no other effect on the basic_string object.
Every object of type basic_string<charT, traits, Allocator> uses an object of type Allocator to allocate and free storage for the contained charT objects as needed.
The Allocator object used is obtained as described in [container.reqmts].
In every specialization basic_string<charT, traits, Allocator>, the type traits shall meet the character traits requirements ([char.traits]).
[Note 1: 
Every specialization basic_string<charT, traits, Allocator> is an allocator-aware container ([container.alloc.reqmts]), but does not use the allocator's construct and destroy member functions ([container.requirements.pre]).
The program is ill-formed if Allocator​::​value_type is not the same type as charT.
— end note]
[Note 2: 
The program is ill-formed if traits​::​char_type is not the same type as charT.
— end note]
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:
  • Passing as an argument to any standard library function taking a reference to non-const basic_string as an argument.203
  • Calling non-const member functions, except operator[], at, data, front, back, begin, rbegin, end, and rend.
For example, as an argument to non-member functions swap() ([string.special]), operator>>() ([string.io]), and getline() ([string.io]), or as an argument to basic_string​::​swap().