This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of Resolved status.
Section: 23.4.3 [basic.string] Status: Resolved Submitter: Michael Bradshaw Opened: 2014-05-27 Last modified: 2017-03-12
Priority: 3
View other active issues in [basic.string].
View all other issues in [basic.string].
View all issues with Resolved status.
Discussion:
Regarding 23.4.3 [basic.string], std::basic_string<charT>::data() returns a const charT* 23.4.3.8.1 [string.accessors]. While this method is convenient, it doesn't quite match std::array<T>::data() [array.data] or std::vector<T>::data() 24.3.11.4 [vector.data], both of which provide two versions (that return T* or const T*). An additional data() method can be added to std::basic_string that returns a charT* so it can be used in similar situations that std::array and std::vector can be used. Without a non-const data() method, std::basic_string has to be treated specially in code that is otherwise oblivious to the container type being used.
Adding a charT* return type to data() would be equivalent to doing &str[0] or &str.front(). Small discussion on the issue can be found here and in the std-discussion thread (which didn't get too much attention). This requires a small change to std::basic_string's definition in 23.4.3 [basic.string] to add the method to std::basic_string, and another small change in 23.4.3.8.1 [string.accessors] to define the new method.[2015-02 Cologne]
Back to LEWG.
[2016-05-22]
Marshall says: this issue has been resolved by P0272R1.
Proposed resolution:
This wording is relative to N3936.
Change class template basic_string synopsis, 23.4.3 [basic.string], as indicated:
namespace std { template<class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> > class basic_string { public: […] // 21.4.7, string operations: const charT* c_str() const noexcept; const charT* data() const noexcept; charT* data() noexcept; allocator_type get_allocator() const noexcept; […] }; }
Add the following sequence of paragraphs following 23.4.3.8.1 [string.accessors] p3, as indicated:
charT* data() noexcept;-?- Returns: A pointer p such that p + i == &operator[](i) for each i in [0,size()].
-?- Complexity: Constant time. -?- Requires: The program shall not alter the value stored at p + size().