C++17

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Versions

C++98

C++03

C++11

C++14

C++17

C++20

C++23

C++26

Current Status

 

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.

Obsolete

Removed:

• std::auto_ptr,
• deprecated function objects,
• std::random_shuffle,
• std::unexpected,
• the obsolete iostreams aliases,
• trigraphs,
• the register keyword,
• bool increment,
• dynamic exception specification

Deprecated:

• std::iterator,
• std::raw_storage_iterator,
• std::get_temporary_buffer,
• std::is_literal_type,
• std::result_of,
• all of <codecvt>

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

New headers

• <any>
• <charconv>
• <execution>
• <filesystem>
• <memory_resource>
• <optional>
• <string_view>
• <variant>

New library features

Utility types

• std::tuple:
  • std::apply
  • std::make_from_tuple
  • deduction guides
• std::any
• std::optional
• std::variant
• searchers
• std::as_const
• std::not_fn

Memory management

• uninitialized memory algorithms
  • std::destroy_at
  • std::destroy
  • std::destroy_n
  • std::uninitialized_move
  • std::uninitialized_value_construct
• 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

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

Algorithms

• std::clamp
• parallel algorithms and execution policies
• std::inclusive_scan
• std::exclusive_scan
• std::gcd
• std::lcm
• std::reduce

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

Numerics

• mathematical special functions
• 3D std::hypot

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

Compiler support

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
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
static_assert with no message  (FTM)*	N3928	6	2.5	19.10*	Yes	4.12	18.0	17.7	11.0	11.0	10.3	17.1.0
Attributes for namespaces and enumerators  (FTM)*  (FTM)*	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  (FTM)*	N4268	6	3.6	19.12*	Yes	5.0	19.0.1	19.1	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  (FTM)*	P0012R1	7	4	19.12*	Yes	4.14	19.0	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)  (FTM)*	P0136R1	7	3.9	19.14 (partial)*	Yes	6.1		19.1	11.0	11.0	10.3	17.1.0
Aggregate classes with base classes  (FTM)*	P0017R1	7	3.9	19.14*	Yes	5.0	19.0.1	19.1	11.0	11.0	10.3	17.1.0
Fold Expressions  (FTM)*	N4295	6	3.6	19.12*	Yes	4.14	19.0	18.1	11.0	11.0	10.3	17.1.0
Lambda capture of *this  (FTM)*	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  (FTM)*	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  (FTM)*	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  (FTM)*	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  (FTM)*	P0035R4	7	4	19.12*	10.0.0*	4.14	19.0	19.1	11.0	11.0	10.3	17.1.0
Non-type template parameters with auto type  (FTM)*	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  (FTM)*	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  (FTM)*	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  (FTM)*	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  (FTM)*	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  (FTM)*	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  (FTM)*	P0522R0	7	4	19.12*	Yes	5.0	19.0.1	19.1	11.0	11.0	10.3	17.1.0
Class template argument deduction  (FTM)*	P0091R3	7	5	19.14*	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

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  (FTM)*	N3911	6.1	3.6	19.0 (2015)*	Yes	17.1.0	N/A	10.3
std::uncaught_exceptions()  (FTM)*	N4259	6.1	3.7	19.0 (2015)*	Yes	17.1.0	N/A	10.3
std::size(), std::empty() and std::data()  (FTM)*	N4280	6	3.6	19.0 (2015)*	Yes	17.1.0	N/A	10.3
std::allocator_traits::is_always_equal  (FTM)*	N4258	6.1	3.7				N/A
std::invoke  (FTM)*	N4169	6.1	3.7				N/A
std::map::try_emplace, std::map::insert_or_assign  (FTM)*	N4279	6.1	3.7				N/A
std::unordered_map::try_emplace, std::unordered_map::insert_or_assign  (FTM)*	N4279	6.1	3.7				N/A
Improving std::pair and std::tuple	N4387	6.1	4	19.0 (Update 2)*	Yes	17.1.0	N/A	10.3
std::bool_constant  (FTM)*	N4389	6.1	3.7	19.0 (2015)*	Yes	17.1.0	N/A	10.3
std::shared_mutex (untimed)  (FTM)*	N4508	6	3.7	19.0 (Update 2)*	Yes	17.1.0	N/A	10.3
Minimal incomplete type support for std::forward_list, std::list, and std::vector  (FTM)*	N4510	3.0	3.6				N/A
Type traits variable templates  (FTM)*	P0006R0	7.1	3.8	19.0 (Update 2)*	Yes	17.1.0	N/A	10.3
Logical operator type traits  (FTM)*	P0013R1	6.1	3.8	19.0 (Update 2)*	Yes	17.1.0	N/A	10.3
std::as_const  (FTM)*	P0007R1	7.1	3.8				N/A
Rounding functions for std::chrono::duration and std::chrono::time_point  (FTM)*	P0092R1	7.1	3.8				N/A
Transparent std::owner_less (std::owner_less<void>)  (FTM)*	P0074R0	7.1	3.8				N/A
std::not_fn  (FTM)*	P0005R4 P0358R1	7.1	3.9	19.12*	Yes	17.1.0	N/A	10.3
Parallel algorithms and execution policies  (FTM)*  (FTM)*	P0024R2	9*	17 (partial)*	19.14*			18.0*
std::clamp()  (FTM)*	P0025R1	7	3.9	19.0 (Update 3)*	10.0.0*	17.1.0	N/A	10.3
(nothrow-)swappable traits  (FTM)*	P0185R1	7.1*	3.9	19.0 (Update 3)*	10.0.0*	17.1.0	N/A	10.3
Polymorphic memory resources  (FTM)*	P0220R1	9.1	16	19.13*	15.0.0*		N/A	10.3
std::apply  (FTM)*	P0220R1	7.1	16				N/A
Searchers  (FTM)*	P0220R1	7.1	16				N/A
std::sample  (FTM)*	P0220R1	7.1	16				N/A
Mathematical special functions  (FTM)*	P0226R1	7		19.14*			N/A	10.3
constexpr std::addressof  (FTM)*	LWG2296	7.1	Yes				N/A
constexpr for std::reverse_iterator, std::move_iterator, std::array and range access  (FTM)*	P0031R0	7.1	4				N/A
constexpr std::atomic<T>::is_always_lock_free  (FTM)*	P0152R1	7.1	3.9				N/A
std::enable_shared_from_this::weak_from_this  (FTM)*	P0033R1	7.1	3.9				N/A
3-argument overload of std::hypot  (FTM)*	P0030R1	7.1	3.9				N/A
std::byte  (FTM)*	P0298R3	7	5	19.11*	Yes	17.1.1	N/A	10.3
std::string_view  (FTM)*	N3921 P0220R1 P0254R2 P0403R1	7.1	4	19.10*	10.0.0*	17.1.0	N/A	10.3
std::any  (FTM)*	P0220R1 P0032R3	7.1	4	19.10*	10.0.0*	17.1.0	N/A	10.3
std::optional  (FTM)*	P0220R1	7.1	4	19.10*	10.0.0*	17.1.0	N/A	10.3
Major portion of C11 standard library	P0063R3	9.1	7	19.0 (2015)* (partial)*	10.0.0*	17.1.1	N/A
Splicing Maps and Sets  (FTM)*	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  (FTM)*	P0088R3	7.1	4	19.10*	10.0.0*	17.1.0	N/A	10.3
std::make_from_tuple()  (FTM)*	P0209R2	7.1	3.9	19.10*	Yes	17.1.0	N/A	10.3
std::has_unique_object_representations  (FTM)*	P0258R2	7.1	6	19.11*	Yes	17.1.1	N/A	10.3
std::gcd() and std::lcm()  (FTM)*	P0295R0	7	4	19.11*	Yes	17.1.0	N/A	10.3
CWG issue 1776: Replacement of class objects containing reference members (std::launder)  (FTM)*	P0137R1	7.1	6				N/A
Extending memory management tools  (FTM)*	P0040R3	7.1	4				N/A
shared_ptr::weak_type  (FTM)*	P0163R0	7.1	3.9				N/A
Elementary string conversions: std::to_chars / std::from_chars  (FTM)*	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
Constexpr for all the member functions of std::chrono::duration and std::chrono::time_point  (FTM)*	P0505R0	7.1	4				N/A
std::shared_ptr<T[]>  (FTM)*	P0497R0	7.1	11				N/A
constexpr std::char_traits  (FTM)*	P0426R1	8.1	4				N/A
File system library (std::filesystem)  (FTM)*	P0218R1 P0219R1	8	7	19.14*	11.0.0*	17.1.1	N/A	10.3
Hardware interference size  (FTM)*	P0154R1	12.1	15 (partial)* 19	19.11*			N/A	10.3
std::scoped_lock  (FTM)*	P0156R2	7	5	19.11*	Yes	17.1.1	N/A	10.3
std::is_aggregate  (FTM)*	LWG2911	7	5	19.15*	Yes	17.1.1	N/A	10.3
std::is_invocable, std::invoke_result  (FTM)*	P0604R0	7.1	Yes				N/A
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*

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.

External links

1.	C++17 - Wikipedia
2.	Working C++17 examples