21 Strings library [strings]

21.3 String classes [string.classes]

21.3.3 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.
In every specialization basic_­string<charT, traits, Allocator>, the type allocator_­traits<Allocator>​::​value_­type shall name the same type as charT.
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.requirements.general].
In every specialization basic_­string<charT, traits, Allocator>, the type traits shall meet the character traits requirements ([char.traits]).
[Note 1:
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.228
  • 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().