C++ Standard Library
C++ Standard Library |
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Containers |
C standard library |
In the C++ programming language, the C++ Standard Library is a collection of classes and functions, which are written in the core language and part of the C++ ISO Standard itself.[1]
Overview
[edit]The C++ Standard Library provides several generic containers, functions to use and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for common tasks such as finding the square root of a number. The C++ Standard Library also incorporates most headers of the ISO C standard library ending with ".h", but their use was deprecated (reverted the deprecation since C++23[2]).[3] C++23 instead considers these headers as useful for interoperability with C, and recommends against their usage outside of programs that are intended to be both valid C and C++ programs. No other headers in the C++ Standard Library end in ".h". Features of the C++ Standard Library are declared within the std
namespace.
The C++ Standard Library is based upon conventions introduced by the Standard Template Library (STL), and has been influenced by research in generic programming and developers of the STL such as Alexander Stepanov and Meng Lee.[4][5] Although the C++ Standard Library and the STL share many features, neither is a strict superset of the other.[citation needed]
A noteworthy feature of the C++ Standard Library is that it not only specifies the syntax and semantics of generic algorithms, but also places requirements on their performance.[6] These performance requirements often correspond to a well-known algorithm, which is expected but not required to be used. In most cases this requires linear time O(n) or linearithmic time O(n log n), but in some cases higher bounds are allowed, such as quasilinear time O(n log2 n) for stable sort (to allow in-place merge sort). Previously, sorting was only required to take O(n log n) on average, allowing the use of quicksort, which is fast in practice but has poor worst-case performance, but introsort was introduced to allow both fast average performance and optimal worst-case complexity, and as of C++11, sorting is guaranteed to be at worst linearithmic. In other cases requirements remain laxer, such as selection, which is only required to be linear on average (as in quickselect),[7] not requiring worst-case linear as in introselect.
The C++ Standard Library underwent ISO standardization as part of the C++ ISO Standardization effort in the 1990s. Since 2011, it has been expanded and updated every three years[8] with each revision of the C++ standard.
Since C++23, the C++ Standard Library can be imported using modules, which were introduced in C++20.
Implementations
[edit]Name | Organization | Homepage | Acronym | Licence | Latest release |
---|---|---|---|---|---|
GNU C++ Standard Library | GNU Project and Free Software Foundation | [1] | libstdc++ | GPLv3 with GCC Runtime Library Exception | New major release once per year |
LLVM C++ Standard Library | LLVM Developer Group | [2] | libc++ | Apache License 2.0 with LLVM Exceptions | Every 2 weeks |
NVIDIA C++ Standard Library | Nvidia | [3] | libcudacxx | Apache License 2.0 with LLVM Exceptions | September 4, 2024 |
Microsoft C++ Standard Library | Microsoft | [4] | MSVC STL | Apache License 2.0 with LLVM Exceptions | Daily |
HPX C++ Standard Library for Parallelism and Concurrency | STELLAR Group | [5] | HPX | Boost Software License 1.0 | May 29, 2024 |
Electronic Arts Standard Template Library | Electronic Arts | [6] | EASTL | BSD 3-Clause License | August 31, 2024 |
Dinkum C++ Library | Dinkumware | [7] | Unknown | Commercial | Unknown |
Cray C++ Standard Library | Cray User Group | [8] | Unknown | Commercial | Unknown |
Discontinued
[edit]Apache C++ Standard Library
[edit]The Apache C++ Standard Library is another open-source implementation. It was originally developed commercially by Rogue Wave Software and later donated to the Apache Software Foundation.[9] However, after more than five years without a release, the board of the Apache Software Foundation decided to end this project and move it to Apache Attic.[10]
See also
[edit]The following libraries implement much of the C++ Standard Library:
Name | Homepage | Description |
---|---|---|
Abseil | [9] | An open source collection of libraries used internally by Google |
Folly | [10] | A variety of C++14 libraries that are used extensively by Facebook |
Bareflank Support Library | [11] | A C++ library where everything can be executed at compile time |
Standard modules
[edit]Ever since the modules were introduced in C++20, there has been no support for standard library modules until C++23. These named modules were added to include all items declared in both global and std
namespaces provided by the importable standard headers. Macros are not allowed to be exportable, so users have to manually include or import headers that emit macros for use.
The C++ standard has reserved std
and std.*
as module names.[11]
The current standard library modules defined by the standard as of C++23 are:
std
- Exports all declarations in namespace
std
and global storage allocation and deallocation functions that are provided by the importable C++ library headers including C library facilities (although declared in standard namespace). std.compat
- Exports the same declarations as the named module
std
, and additionally exports functions in global namespace in C library facilities. It thus contains "compat" in the name, meaning compatibility with C.
As of currently, the above modules export the entire C++ standard library, meaning that the standard library must be imported in its entirety. Furthermore, modules do not allow for granular imports of specific namespaces or classes within a module, nor does it allow for using wildcard imports, unlike Java or Rust which do allow for the aforementioned.
Like Java's packages, C++ modules do not have a hierarchical system, but typically use a hierarchical naming convention. In other words, C++ does not have "submodules", meaning the .
symbol which may be included in a module name bears no syntactic meaning and is used only to suggest the association of a module. This means that std.compat
is not a submodule of std
.
It has been proposed that additional modules providing other subsets of the standard library be added.[12][13] These include:
std.fundamental
- Exports the utility facilities within the C++ standard library.
std.core
- Exports everything in
std.fundamental
, as well as container facilities and the Standard Template Library (STL), and other data types such as strings, regular expressions, and smart pointers. std.io
- Exports C++ facilities for input/output.
std.os
- Exports C++ facilities for interfacing with the operating system.
std.concurrency
- Exports C++ facilities for concurrent programming.
std.math
- Exports C++ facilities for mathematics.
Standard headers
[edit]The following files contain the declarations of the C++ Standard Library.
General
[edit]<any>
- New in C++17. Provides a type-erased class
std::any
. <atomic>
- New in C++11. Provides class template
std::atomic
, its several template specializations, and more atomic operations. <chrono>
- Provides time elements, such as
std::chrono::duration
,std::chrono::time_point
, and clocks. Since C++20, a hefty amount of temporal features were added: calendars, time zones, more clocks, and string chrono formatting. <concepts>
- New in C++20. Provides fundamental library concepts.
<expected>
- New in C++23. Provides class template
std::expected
, a result type. <functional>
- Provides several function objects, designed for use with the standard algorithms.
<generator>
- New in C++23. Provides a coroutine generator that additionally supports nested yield operations on ranges.
<memory>
- Provides facilities for memory management in C++, including the class template
std::unique_ptr
. <memory_resource>
- New in C++17. Provides facilities for creating polymorphic memory allocators whose behaviors can change at runtime.[14]
<optional>
- New in C++17. Provides class template
std::optional
, an optional type. <scoped_allocator>
- New in C++11. Provides
std::scoped_allocator_adaptor
. <stacktrace>
- New in C++23. Provides stack trace operations.
<stdexcept>
- Contains standard exception classes such as
std::logic_error
andstd::runtime_error
, both derived fromstd::exception
. <system_error>
- New in C++11. Defines
std::error_code
<tuple>
- New in C++11 and TR1. Provides a class template
std::tuple
, a tuple. <type_traits>
- New in C++11. Provides metaprogramming facilities working with types.
<utility>
- Provides various utilities: class template
std::pair
(two-member tuples), compile-time integer sequences, helpers in constructing vocabulary types, functions such asstd::move
andstd::forward
, and many more. The namespacestd::rel_ops
for automatically generating comparison operators is deprecated in C++20 in favor of new defaulted comparison operators. <variant>
- New in C++17. Provides a class template
std::variant
, a tagged union type.
Language support
[edit]<compare>
- New in C++20. Provides three-way comparison operator support.
<coroutine>
- New in C++20. Provides coroutine support.
<exception>
- Provides several types and functions related to exception handling, including
std::exception
, the base class of all exceptions thrown by the Standard Library. <initializer_list>
- New in C++11. Provides initializer list support.
<limits>
- Provides the class template
std::numeric_limits
, used for describing properties of fundamental numeric types. <new>
- Provides operators
new
anddelete
and other functions and types composing the fundamentals of C++ memory management. <source_location>
- New in C++20. Provides capturing source location information as alternative to predefined macros such as
__LINE__
. <stdfloat>
- New in C++23. Provides conditional support for extended floating-point types.
<typeinfo>
- Provides facilities for working with C++ run-time type information.
<version>
- New in C++20. Provides information about the implementation of the C++ standard library.[15]
Containers
[edit]<array>
- New in C++11 and TR1. Provides the container class template
std::array
, a container for a fixed sized array. <bitset>
- Provides the specialized container class
std::bitset
, a bit array. <deque>
- Provides the container class template
std::deque
, a double-ended queue. <flat_map>
- New in C++23. Provides the container adaptor class templates
std::flat_map
andstd::flat_multimap
. <flat_set>
- New in C++23. Provides the container adaptor class templates
std::flat_set
andstd::flat_multiset
. <forward_list>
- New in C++11 and TR1. Provides the container class template
std::forward_list
, a singly linked list. <list>
- Provides the container class template
std::list
, a doubly linked list. <map>
- Provides the container class templates
std::map
andstd::multimap
, sorted associative array and multimap. <mdspan>
- New in C++23. Provides the class template
std::mdspan
, analogous tostd::span
but the view is multidimensional. <queue>
- Provides the container adapter class
std::queue
, a single-ended queue, andstd::priority_queue
, a priority queue. <set>
- Provides the container class templates
std::set
andstd::multiset
, sorted associative containers or sets. <span>
- New in C++20. Provides the class template
std::span
, a non-owning view that refers to any contiguous range. <stack>
- Provides the container adapter class
std::stack
, a stack. <unordered_map>
- New in C++11 and TR1. Provides the container class template
std::unordered_map
andstd::unordered_multimap
, hash tables. <unordered_set>
- New in C++11 and TR1. Provides the container class template
std::unordered_set
andstd::unordered_multiset
. <vector>
- Provides the container class template
std::vector
, a dynamic array.
Iterators and ranges
[edit]<algorithm>
- Provides definitions of many algorithms for use with containers and other ranges.
<execution>
- New in C++17. Provides execution policies for parallelized algorithms.
<iterator>
- Provides classes and templates for working with iterators.
<numeric>
- Generalized numeric algorithms.
<ranges>
- New in C++20. Provides ranges facilities and lazily evaluated adaptors.
Localization
[edit]<codecvt>
- Provides code conversion facets for various character encodings. This header is deprecated since C++17.
<locale>
- Defines classes and declares functions that encapsulate and manipulate the information peculiar to a locale.
<text_encoding>
- New in C++26. Provides text encoding identifications.
Strings
[edit]<charconv>
- New in C++17. Provides a locale-independent, non-allocating, and non-throwing string conversion utilities from/to integers and floating point.
<format>
- New in C++20. Provides a modern way of formatting strings including
std::format
. <string>
- Provides the C++ standard string classes and templates.
<string_view>
- New in C++17. Provides class template
std::basic_string_view
, an immutable non-owning view to any string. <regex>
- New in C++11. Provides utilities for pattern matching strings using regular expressions.
Streams, files, and input/output
[edit]<filesystem>
- New in C++17. Provides facilities for file system operations and their components.
<fstream>
- Provides facilities for file-based input and output. See fstream.
<iomanip>
- Provides facilities to manipulate output formatting, such as the base used when formatting integers and the precision of floating-point values.
<ios>
- Provides several types and functions basic to the operation of iostreams.
<iosfwd>
- Provides forward declarations of several I/O-related class templates.
<iostream>
- Provides C++ input and output fundamentals. See iostream.
<istream>
- Provides
std::istream
and other supporting classes for input. <ostream>
- Provides
std::ostream
and other supporting classes for output. <print>
- New in C++23. Provides formatted output utilities such as
std::print
supported for both C and C++ streams. <spanstream>
- New in C++23. Provides
std::spanstream
and other fixed character buffer I/O streams. <sstream>
- Provides
std::stringstream
and other supporting classes for string manipulation. <streambuf>
- Provides reading and writing functionality to/from certain types of character sequences, such as external files or strings.
<syncstream>
- New in C++20. Provides
std::osyncstream
and other supporting classes for synchronized output streams.
Thread support library
[edit]<barrier>
- New in C++20. Provides
std::barrier
, a reusable thread barrier. <condition_variable>
- New in C++11. In 32.6-1, condition variables provide synchronization primitives used to block a thread until notified by some other thread that some condition is met or until a system time is reached.
<future>
- New in C++11. In 32.9.1-1, this section describes components that a C++ program can use to retrieve in one thread the result (value or exception) from a function that has run in the same thread or another thread.
<hazard_pointer>
- New in C++26. Provides
std::hazard_pointer
. <latch>
- New in C++20. Provides
std::latch
, a single-use thread barrier. <mutex>
- New in C++11. In 32.5-1, this section provides mechanisms for mutual exclusion: mutexes, locks, and call once.
<rcu>
- New in C++26. Provides read-copy-update mechanisms.
<shared_mutex>
- New in C++14. Provides facitility for shared mutual exclusion.
<semaphore>
- New in C++20. Provides semaphore that models non-negative resource count.
<stop_token>
- New in C++20. In 32.3.1-1, this section describes components that can be used to asynchronously request that an operation stops execution in a timely manner, typically because the result is no longer required. Such a request is called a stop request.
<thread>
- New in C++11. Provide class and namespace for working with threads.
Numerics library
[edit]Components that C++ programs may use to perform seminumerical operations.
<bit>
- New in C++20. Provides bit manipulation facility.
<complex>
- Defines a class template
std::complex
, and numerous functions for representing and manipulating complex numbers. <numbers>
- New in C++20. Provides mathematical constants defined in namespace
std::numbers
. <random>
- New in C++11. Facility for generating (pseudo-)random numbers and distributions.
<ratio>
- New in C++11. Provides compile-time rational arithmetic based on class templates.
<valarray>
- Defines five class templates (
std::valarray
,std::slice_array
,std::gslice_array
,std::mask_array
, andstd::indirect_array
), two classes (std::slice
andstd::gslice
), and a series of related function templates for representing and manipulating arrays of values.
C standard library
[edit]Each header from the C Standard Library is included in the C++ Standard Library under a different name, generated by removing the .h, and adding a 'c' at the start; for example, 'time.h' becomes 'ctime'. The only difference between these headers and the traditional C Standard Library headers is that where possible the functions should be placed into the std::
namespace. In ISO C, functions in the standard library are allowed to be implemented by macros, which is not allowed by ISO C++.
See also
[edit]References
[edit]- ^ ISO/IEC 14882:2003(E) Programming Languages – C++ §17-27
- ^ Thomas Köppe (11 June 2021). "Clarifying the status of the "C headers"".
- ^ ISO/IEC 14882:2003(E) Programming Languages – C++ §D.5
- ^ Bjarne Stroustrup (1994). The Design and Evolution of C++ §8.5. Addison Wesley. ISBN 0-201-54330-3.
- ^ Alexander Stepanov, Meng Lee (1 August 1994). "The Standard Template Library". HP Labs. Retrieved 22 October 2017.
- ^ "Generic Algorithms", David Musser
- ^ "std::nth_element". cppreference.com. Retrieved 20 March 2018.
- ^ "C++ IS Schedule", Herb Sutter
- ^ Apache C++ Standard Library
- ^ Brett Porter (18 July 2013). "Apache C++ Standard Library and the Attic". stdcxx-dev mailing list. Retrieved 27 February 2014.
- ^ C++ Standards Committee. (2022). P2465R3 - C++ Modules: Design and Evolution. Retrieved from https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2465r3.pdf
- ^ C++ Standards Committee. (2018). P0581R1 - Modules for C++. Retrieved from https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0581r1.pdf
- ^ C++ Standards Committee. (2021). P2412R0 - Further refinements to the C++ Modules Design. Retrieved from https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2412r0.pdf
- ^ Filipek, Bartlomiej. "Polymorphic Allocators, std::vector Growth and Hacking". Retrieved 30 April 2021.
- ^ "Working Draft, Standard for Programming Language C++" (PDF). open-std.org. ISO/IEC. 1 April 2020. p. 492. Archived (PDF) from the original on 27 April 2020. Retrieved 30 April 2021.
Further reading
[edit]- Stroustrup, Bjarne (2013). The C++ Programming Language. Addison-Wesley. ISBN 978-0321563842.
- Josuttis, Nicolai (2012). The C++ Standard Library – A Tutorial and Reference. Addison-Wesley. ISBN 978-0-321-62321-8.
- Van Weert, Peter; Gregoire, Marc (14 June 2016). C++ Standard Library Quick Reference. Apress. ISBN 978-1484218754. Archived from the original on 16 May 2021. Retrieved 24 March 2017.
External links
[edit]- C++ Standard Library reference
- Microsoft C++ Standard Library Reference
- Rogue Wave SourcePro C++ documentation
- Apache C++ Standard Library Wiki, retired 15 May 2014 (based on Rogue Wave C++ Standard Library 4.1.0)
- STLport C++ Standard Library documentation
- The GNU C++ Library online documentation
- LLVM/Clang C++ Standard Library documentation