C++17
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C++17 is a major version that follows the minor version C++14 and introduces new language and library features. The standard was published in December 2017.
The following features were merged into C++17:
- From the File System TS: the filesystem library.
- From the Library fundamentals v1 TS: features, including std::any, std::optional, std::string_view, std::apply, polymorphic allocators, searchers.
- From Library fundamentals v2 TS: std::void_t, std::conjunction, std::disjunction, std::negation, std::not_fn, std::gcd, std::lcm.
- From Parallelism v1 TS: features, including execution policies, std::reduce, std::inclusive_scan, std::exclusive_scan, but removing
exception_list
. - From Mathematical special functions IS: mathematical special functions.
- From C11: std::aligned_alloc, std::timespec_get.
This section is incomplete |
Contents |
[edit] Obsolete
[edit] Removed:
- std::auto_ptr,
- deprecated function objects,
- std::random_shuffle,
- std::unexpected,
- the obsolete
iostream
s aliases, - trigraphs,
- the register keyword,
-
bool
increment, - dynamic exception specification
[edit] Deprecated:
- std::iterator,
- std::raw_storage_iterator,
- std::get_temporary_buffer,
- std::is_literal_type,
- std::result_of,
- all of <codecvt>
[edit] New language features
-
u8
character literal - made noexcept part of type system
- new order of evaluation rules
- lambda capture of *this
- constexpr
- compile-time if constexpr
- constexpr lambda
- Variables
- inline variables
- structured bindings
- initializers for if and switch
- guaranteed copy elision
- temporary materialization
- Templates
- fold-expressions ( ... )
- class template argument deduction tuple t(4, 3, 2.5)
- non-type template parameters declared with
auto
- Namespaces
- simplified nested namespaces
-
using
-declaration declaring multiple names - attribute namespaces don't have to repeat
- new attributes:
-
[[fallthrough]]
-
[[maybe_unused]]
-
[[nodiscard]]
-
- __has_include
[edit] New headers
[edit] New library features
[edit] Utility types
[edit] Memory management
- uninitialized memory algorithms
- weak_from_this
- std::pmr::memory_resource and std::polymorphic_allocator
- std::aligned_alloc
- transparent std::owner_less
- array support for std::shared_ptr
- allocation functions with explicit alignment
[edit] Compile-time programming
- std::byte
- std::conjunction/std::disjunction/std::negation
- type trait variable templates (
xxx_+v
) - std::is_swappable
- std::is_invocable
- std::is_aggregate
- std::has_unique_object_representations
[edit] Algorithms
- std::clamp
- parallel algorithms and execution policies
- std::inclusive_scan
- std::exclusive_scan
- std::gcd
- std::lcm
- std::reduce
[edit] Iterators and containers
- map/set extract and map/set merge
- map/unordered_map try_emplace and insert_or_assign
- contiguous iterators (LegacyContiguousIterator)
- non-member std::size/std::empty/std::data
[edit] Numerics
[edit] Others
- cache line interface
- std::launder
- std::uncaught_exceptions
- std::to_chars/std::from_chars
- std::atomic<T>::is_always_lock_free
- std::scoped_lock
- std::timespec_get
- rounding functions for std::chrono::duration and std::chrono::time_point
[edit] Defect reports
[edit] Compiler support
[edit] C++17 core language features
C++17 feature |
Paper(s) |
GCC |
Clang |
MSVC |
Apple Clang |
EDG eccp |
Intel C++ |
Nvidia HPC C++ (ex PGI)* |
Nvidia nvcc |
Cray |
Embarcadero C++ Builder |
IBM Open XL C++ for AIX |
|
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
DR11: New auto rules for direct-list-initialization
|
N3922 | 5 | 3.8 | 19.0 (2015)* | Yes | 4.10.1 | 17.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
static_assert with no message | N3928 | 6 | 2.5 | 19.10* | Yes | 4.12 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
typename in a template template parameter
|
N4051 | 5 | 3.5 | 19.0 (2015)* | Yes | 4.10.1 | 17.0 | 17.7 | Yes* | 11.0 | 10.3 | 17.1.0 | |
Removing trigraphs | N4086 | 5 | 3.5 | 16.0* | Yes | 5.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | ||
Nested namespace definition | N4230 | 6 | 3.6 | 19.0 (Update 3)* | Yes | 4.12 | 17.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Attributes for namespaces and enumerators | N4266 | 4.9 (partial)* 6 |
3.6 | 19.0 (2015)* | Yes | 4.11 | 17.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
u8 character literals
|
N4267 | 6 | 3.6 | 19.0 (2015)* | Yes | 4.11 | 17.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Allow constant evaluation for all non-type template arguments | N4268 | 6 | 3.6 | 19.12* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Fold Expressions | N4295 | 6 | 3.6 | 19.12* | Yes | 4.14 | 19.0 | 18.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Unary fold expressions and empty parameter packs | P0036R0 | 6 | 3.9 | 19.12* | Yes | 4.14 | 19.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Remove Deprecated Use of the register Keyword | P0001R1 | 7 | 3.8 | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Remove Deprecated operator++(bool)
|
P0002R1 | 7 | 3.8 | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Make exception specifications part of the type system | P0012R1 | 7 | 4 | 19.12* | Yes | 4.14 | 19.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Aggregate classes with base classes | P0017R1 | 7 | 3.9 | 19.14* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
__has_include in preprocessor conditionals | P0061R1 | 5 | Yes | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
DR11: New specification for inheriting constructors (DR1941 et al) | P0136R1 | 7 | 3.9 | 19.14 (partial)* | Yes | 6.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | ||
Lambda capture of *this
|
P0018R3 | 7 | 3.9 | 19.11* | Yes | 4.14 | 19.0 | 18.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Direct-list-initialization of enumerations | P0138R2 | 7 | 3.9 | 19.11* | Yes | 4.14 | 18.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
constexpr lambda expressions | P0170R1 | 7 | 5 | 19.11* | Yes | 4.14 | 19.0 | 18.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Differing begin and end types in range-based for | P0184R0 | 6 | 3.9 | 19.10* | Yes | 4.12 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
[[fallthrough]] attribute
|
P0188R1 | 7 | 3.9 | 19.10* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
[[nodiscard]] attribute
|
P0189R1 | 7 | 3.9 | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
[[maybe_unused]] attribute
|
P0212R1 | 7 | 3.9 | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Hexadecimal floating-point literals | P0245R1 | 3.0 | Yes | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Using attribute namespaces without repetition | P0028R4 | 7 | 3.9 | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Dynamic memory allocation for over-aligned data | P0035R4 | 7 | 4 | 19.12* | 10.0.0* | 4.14 | 19.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Class template argument deduction | P0091R3 | 7 | 5 | 19.14* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Non-type template parameters with auto type
|
P0127R2 | 7 | 4 | 19.14* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Guaranteed copy elision | P0135R1 | 7 | 4 | 19.13* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Replacement of class objects containing reference members | P0137R1 | 7 | 6 | 19.14* | Yes | 5.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | ||
Stricter expression evaluation order | P0145R3 | 7 | 4 | 19.14* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Structured Bindings | P0217R3 | 7 | 4 | 19.11* | Yes | 4.14 | 19.0 | 18.1 | 11.0* | 11.0 | 10.3 | 17.1.0 | |
Ignore unknown attributes | P0283R2 | Yes | 3.9 | 19.11* | Yes | 4.13 | 18.0 | 17.7 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
constexpr if statements | P0292R2 | 7 | 3.9 | 19.11* | Yes | 4.14 | 19.0 | 18.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
init-statements for if and switch | P0305R1 | 7 | 3.9 | 19.11* | Yes | 4.14 | 18.0 | 18.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Inline variables | P0386R2 | 7 | 3.9 | 19.12* | Yes | 4.14 | 19.0 | 18.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Removing dynamic exception specifications | P0003R5 | 7 | 4 | 19.10* | Yes | 4.14 | 19.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
Pack expansions in using-declarations | P0195R2 | 7 | 4 | 19.14* | Yes | 5.0 | 19.0 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
DR98: Matching of template template-arguments excludes compatible templates | P0522R0 | 7 | 4 | 19.12* | Yes | 5.0 | 19.0.1 | 19.1 | 11.0 | 11.0 | 10.3 | 17.1.0 | |
C++17 feature |
Paper(s) |
GCC |
Clang |
MSVC |
Apple Clang |
EDG eccp |
Intel C++ |
Nvidia HPC C++ (ex PGI)* |
Nvidia nvcc |
Cray |
Embarcadero C++ Builder |
IBM Open XL C++ for AIX |
[edit] C++17 library features
C++17 feature |
Paper(s) |
GCC libstdc++ |
Clang libc++ |
MSVC STL |
Apple Clang* |
IBM Open XL C/C++ for AIX* |
Intel Parallel STL |
Embarcadero C++ Builder* |
|
---|---|---|---|---|---|---|---|---|---|
std::void_t | N3911 | 6 | 3.6 | 19.0 (2015)* | Yes | 17.1.0 | N/A | 10.3 | |
std::uncaught_exceptions() | N4259 | 6 | 3.7 | 19.0 (2015)* | Yes | 17.1.0 | N/A | 10.3 | |
std::size(), std::empty() and std::data() | N4280 | 6 | 3.6 | 19.0 (2015)* | Yes | 17.1.0 | N/A | 10.3 | |
Improving std::pair and std::tuple | N4387 | 6 | 4 | 19.0 (Update 2)* | Yes | 17.1.0 | N/A | 10.3 | |
std::bool_constant | N4389 | 6 | 3.7 | 19.0 (2015)* | Yes | 17.1.0 | N/A | 10.3 | |
std::shared_mutex (untimed) | N4508 | 6 | 3.7 | 19.0 (Update 2)* | Yes | 17.1.0 | N/A | 10.3 | |
Type traits variable templates | P0006R0 | 7 | 3.8 | 19.0 (Update 2)* | Yes | 17.1.0 | N/A | 10.3 | |
Logical operator type traits | P0013R1 | 6 | 3.8 | 19.0 (Update 2)* | Yes | 17.1.0 | N/A | 10.3 | |
Parallel algorithms and execution policies | P0024R2 | 9* | 17 (partial)* |
19.14* | 18.0* | ||||
std::clamp() | P0025R1 | 7 | 3.9 | 19.0 (Update 3)* | 10.0.0* | 17.1.0 | N/A | 10.3 | |
Hardware interference size | P0154R1 | 12 | 15 (partial)* 19 |
19.11* | N/A | 10.3 | |||
(nothrow-)swappable traits | P0185R1 | 7 | 3.9 | 19.0 (Update 3)* | 10.0.0* | 17.1.0 | N/A | 10.3 | |
File system library (std::filesystem) | P0218R1 | 8 | 7 | 19.14* | 11.0.0* | 17.1.1 | N/A | 10.3 | |
std::string_view | N3921 P0220R1 |
7 | 4 | 19.10* | 10.0.0* | 17.1.0 | N/A | 10.3 | |
std::any | P0220R1 | 7 | 4 | 19.10* | 10.0.0* | 17.1.0 | N/A | 10.3 | |
std::optional | P0220R1 | 7 | 4 | 19.10* | 10.0.0* | 17.1.0 | N/A | 10.3 | |
Polymorphic memory resources | P0220R1 | 9 | 16 | 19.13* | 15.0.0* | N/A | 10.3 | ||
Mathematical special functions | P0226R1 | 7 | 19.14* | N/A | 10.3 | ||||
Major portion of C11 standard library | P0063R3 | 9 | 7 | 19.0 (2015)* (partial)* |
10.0.0* | 17.1.1 | N/A | ||
Splicing Maps and Sets | P0083R3 | 7 | 8 | 19.12* | 10.0.0* | 17.1.1 | N/A | ||
return type of emplace* functions of some containers changed from void to reference
|
P0084R2 | 7.1 | 4.0 | 19.11* | Yes | 17.1.0 | N/A | ||
std::variant | P0088R3 | 7 | 4 | 19.10* | 10.0.0* | 17.1.0 | N/A | 10.3 | |
std::make_from_tuple() | P0209R2 | 7 | 3.9 | 19.10* | Yes | 17.1.0 | N/A | 10.3 | |
std::has_unique_object_representations | P0258R2 | 7 | 6 | 19.11* | Yes | 17.1.1 | N/A | 10.3 | |
std::gcd() and std::lcm() | P0295R0 | 7 | 4 | 19.11* | Yes | 17.1.0 | N/A | 10.3 | |
std::not_fn | P0005R4 P0358R1 |
7 | 3.9 | 19.12* | Yes | 17.1.0 | N/A | 10.3 | |
Elementary string conversions: std::to_chars/std::from_chars | P0067R5 | 8* 11 |
7* 14* 20* |
19.14** 19.24* |
10.0.0** | 17.1.1* | N/A | 10.3* | |
std::shared_ptr and std::weak_ptr with array support | P0414R2 | 7 | 11 | 19.12* | 12.0.0* | 17.1.1 | N/A | 10.3 | |
std::scoped_lock | P0156R2 | 7 | 5 | 19.11* | Yes | 17.1.1 | N/A | 10.3 | |
std::byte | P0298R3 | 7 | 5 | 19.11* | Yes | 17.1.1 | N/A | 10.3 | |
std::is_aggregate | LWG2911 | 7 | 5 | 19.15* | Yes | 17.1.1 | N/A | 10.3 | |
DR17: std::hash<std::filesystem::path> | LWG3657 | 11.4 | 17 | 19.32* | N/A | ||||
C++17 feature |
Paper(s) |
GCC libstdc++ |
Clang libc++ |
MSVC STL |
Apple Clang* |
IBM Open XL C/C++ for AIX* |
Intel Parallel STL |
Embarcadero C++ Builder* |
[edit] Notes
- As of 2020-11-20, the latest release of Oracle Developer Studio is 12.6. Its documentation does not mention C++17.
- Cray compiler may have support for some features earlier than 11.0. That version is when it became a derivative of Clang, gaining all of the attendant language feature support of the base compiler. See Cray/HPE document S-2179.
* - hover over a cell marked with the star * to see additional pop-up notes.
DRnn - the number nn after "DR" denotes target C++ revision the Defect Report is applied to, e.g., DR20 → C++20.
[edit] External links
C++17 - Wikipedia | |
Working C++17 examples |