C++ language support

Supported features

The following tables list support for ISO C++ standard features available on Apple platforms and in the Apple Clang compiler, as well as links to related documentation. While most features are supported by all Apple operating systems, some features depend on specific OS capabilities or require support in the libc++.dylib shared library provided with the OS. Code that uses those features should be guarded by the minimal deployment target check as noted.

C++26 (expected)

Feature	Paper	Notes
Remove undefined behavior from lexing	P2621R2 (DR)	Requires Xcode 16
Making non-encodable string literals ill-formed	P1854R4 (DR)	Requires Xcode 16
Add @, $, and ` to the basic character set	P2558R2	Requires Xcode 15 or later
Unevaluated strings	P2361R6	Requires Xcode 16
Features implemented in the libc++ library
Testing for success or failure of <charconv> functions	P2497R0	Requires Xcode 16
ADL-proof std::projected	P2538R1	Requires Xcode 16
Native handles and file streams	P1759R6	Requires Xcode 16
Interfacing bitset with string_view	P2697R1	Requires Xcode 16
Saturation arithmetic	P0543R3	Requires Xcode 16
Runtime format strings	P2905R2	Requires Xcode 16
Runtime format strings II	P2918R2	Requires Xcode 16
Fix formatting of code units as integers (Dude, where’s my char?)	P2909R4	Requires Xcode 16
std::span over an initializer list	P2447R6	Requires Xcode 16
span.at()	P2821R5	Requires Xcode 16
Remove Deprecated std::allocator Typedef From C++26	P2868R3	Requires Xcode 16
Remove basic_string::reserve() From C++26	P2870R3	Requires Xcode 16
Remove Deprecated Unicode Conversion Facets from C++26	P2871R3	Requires Xcode 16

C++23

Feature	Paper	Notes
The Equality Operator You Are Looking For	P2468R2	Requires Xcode 16
Labels at the end of compound statements	P2324R2	Requires Xcode 16
static operator()	P1169R4	Requires Xcode 16
char8_t Compatibility and Portability Fix	P2513R3	Requires Xcode 16
static operator[]	P2589R1	Requires Xcode 16
Permitting static constexpr variables in constexpr functions	P2647R1	Requires Xcode 16
consteval needs to propagate up	P2564R3(DR)	Requires Xcode 16
Referencing The Unicode Standard	P2736R2	Requires Xcode 16
De-deprecating volatile compound operations.	P2327R1	Requires Xcode 15 or later
Support for #warning	P2437R1	Requires Xcode 15 or later
Remove non-encodable wide character literals and multicharacter wide character literals	P2362R3	Requires Xcode 15 or later
Delimited escape sequences	P2290R3	Requires Xcode 15 or later
Named universal character escapes	P2071R2	Requires Xcode 15 or later
Support for UTF-8 as a portable source file encoding	P2295R6	Requires Xcode 15 or later
Relax requirements on wchar_t to match existing practices	P2460R2	Requires Xcode 15 or later
Multidimensional subscript operator	P2128R6	Requires Xcode 14.3 or later
Non-literal variables (and labels and gotos) in constexpr functions	P2242R3	Requires Xcode 14.3 or later
auto(x): decay-copy in the language	P0849R8	Requires Xcode 14.3 or later
Literal suffix uz, z for size_t, ssize_t	P0330R8
Make () in lambdas optional in all cases	P1102R2
if consteval	P1938R3
Allow duplicate attributes	P2156R1
Narrowing contextual conversions to bool	P1401R5
Trimming whitespaces before line splicing	P2223R2
C++ identifier syntax using unicode standard annex 31	P1949R7
Mixed string literal concatenation	P2201R1
Character sets and encodings	P2314R4
Consistent character literal encoding	P2316R2
Preprocessing directives elifdef and elifndef	P2334R1
Extend init-statement to allow alias-declaration	P2360R0
Attributes on lambda expressions	P2173R1
Make declaration order layout mandated	P1847R4
Features implemented in the libc++ library
starts_with and ends_with	P1659R3	Requires Xcode 16
views::chunk_by	P2443R1	Requires Xcode 16
std::ranges::contains	P2302R4	Requires Xcode 16 Not supported: std::ranges::contains_subrange
Support exclusive mode for fstreams	P2467R1	Requires Xcode 16
Add a conditional noexcept specification to std::apply	P2517R1	Requires Xcode 16
Should the output of std::print to a terminal be synchronized with the underlying stream?	P2539R4	Requires Xcode 16
Deprecate numeric_limits::has_denorm	P2614R2	Requires Xcode 16
Formatting ranges	P2286R8	Requires Xcode 15.3 or later
ranges::to : A function to convert any range to a container	P1206R7	Requires Xcode 15.3 or later
move_iterator<T*> should be a random access iterator	P2520R0	Requires Xcode 15.3 or later
constexpr type_info::operator==()	P1328R1	Requires Xcode 15.3 or later
Formatting thread::id	P2693R1	Requires Xcode 15.3 or later
Monadic operations for std::expected	P2505R5	Requires Xcode 15.3 or later
Making multi-param constructors of views explicit	P2711R1	Requires Xcode 15.3 or later
std::invoke_r	P2136R3	Requires Xcode 15.3 or later
Relaxing range adaptors to allow for move only types	P2494R2	Requires Xcode 15.3 or later
Improving default container formatting	P2585R1	Requires Xcode 15.3 or later
std::ranges::views::repeat	P2474R2	Requires Xcode 15.3 or later
std::mdspan	P0009R18	Requires Xcode 15.3 or later
Formatted output	P2093R14	Requires Xcode 15.3 or later
Add the missing empty to mdspan	P2613R1	Requires Xcode 15.3 or later
mdspan: rename pointer and contiguous	P2604R0	Requires Xcode 15.3 or later
string_view range constructor should be explicit	P2499R0	Requires Xcode 15 or later
A more constexpr bitset	P2417R2	Requires Xcode 15 or later
forward_like	P2445R1	Requires Xcode 15 or later
Making std::unique_ptr constexpr	P2273R3	Requires Xcode 15 or later
Add constexpr modifiers to functions to_chars and from_chars for integral types in <charconv> header	P2291R3	Requires Xcode 15 or later
std::string::substr() &&	P2438R2	Requires Xcode 15 or later
std::expected	P0323R12	Requires Xcode 15 or later
views::as_rvalue	P2446R2	Requires Xcode 15 or later
std::unexpected should have error() as member accessor	P2549R1	Requires Xcode 15 or later
Conditionally borrowed ranges	P2017R1	Requires Xcode 15 or later
Function to mark unreachable code std::unreachable()	P0627R6	Requires Xcode 14.3 or later
Type trait to detect scoped enumerations std::is_scoped_enum	P1048R1
contains() function for basic_string and basic_string_view	P1679R3
std::to_underlying for enumerations	P1682R3
std::visit() for classes derived from std::variant	P2162R2
Prevent overconstraining allocators in container deduction guides	P1518R2
Prohibit basic_string and basic_string_view construction from nullptr	P2166R1
Require span & basic_string_view to be trivially copyable	P2251R1

C++20

Feature	Paper	Notes
typename optional in more contexts	P0634R3	Requires Xcode 16
Structured binding extensions	P1091R3	Requires Xcode 16
	P1381R1
Parenthesized initialization of aggregates	P0960R3	Requires Xcode 16
	P1975R0
Concepts	P0734R0	Not supported: papers P2103R0, DR1496, DR1734, P0848R3
	P1084R2
	P1141R2
	P1616R1
	P1452R2
	P1972R0
	P1980R0
	P2493R0
	P2092R0
Immediate functions (consteval)	P1073R3	Requires Xcode 15 or later
	P1937R2
Default member initializers for bit-fields	P0683R1
Fix const-qualified (const&-qualified) pointers to members	P0704R1
Allow lambda-capture [=, this]	P0409R2
__VA_OPT__ for comma omission and comma deletion	P0306R4
	P1042R1
Designated initializers	P0329R4
Familiar template-parameter-list syntax for generic lambdas	P0428R2
Range-based for statements with initializer	P0614R1
ADL and function templates that are not visible	P0846R0
const mismatch with defaulted copy constructor	P0641R2
Consistent comparison (operator<=>)	P0515R3
	P0905R1
	P1120R0
	P1185R2
	P1186R3
	P1630R1
	P1946R0
	P1959R0
	P2085R0
Relaxing access checking on specializations	P0692R1
Default constructible and assignable stateless lambdas	P0624R2
Allowing lambdas in unevaluated contexts	P0315R4	Not supported: [temp.deduct/9]
[[no_unique_address]] attribute	P0840R2
[[likely]] and [[unlikely]] attributes	P0479R5
Pack expansion in lambda init-capture	P0780R2
Relaxations of constexpr restrictions	P1064R0
	P1002R1
	P1327R1
	P1330R0
	P1331R2
	P1668R1
	P0784R7
Prohibit aggregates with user-declared constructors	P1008R1
Feature test macros	P0941R2
explicit(bool): conditionally explicit constructor	P0892R2
Signed integers are two’s complement	P1236R1
char8_t: A type for UTF-8 characters and strings	P0482R6
std::is_constant_evaluated	P0595R2
Nested inline namespaces	P1094R2
Stronger unicode requirements	P1041R4
	P1139R2
Coroutines	P0912R5
Deprecate comma operator in subscripting expressions like a[b,c]	P1161R3
Deprecate some problematic uses of volatile	P1152R4
[[nodiscard("with reason")]]	P1301R4
using enum	P1099R5
Permit conversions to arrays of unknown bound	P0388R4
constinit	P1143R2
Pseudo-destructors end object lifetimes	P0593R6 (DR)
Implicit move for more local objects and rvalue references	P1825R0 (DR)
Features implemented in the libc++library
Floating Point Atomic	P0020R6	Requires Xcode 16
Text formatting (std::format)	P0645R10	Requires Xcode 15.3 or later
Efficient access to basic_stringbuf’s buffer	P0408R7	Requires Xcode 15.3 or later
Utility functions to implement uses-allocator construction	P0591R4	Requires Xcode 15 or later
char8_t: A type for UTF-8 characters and strings	P0482R6	Requires Xcode 15 or later
nodiscard in the Library	P0600R1	Requires Xcode 15 or later
polymorphic_allocator<> as a vocabulary type	P0339R6	Requires Xcode 15 or later
Constexpr for std::complex	P0415R1	Requires Xcode 15 or later
Adopt source_location for C++20	P1208R6	Requires Xcode 15 or later
Input Range Adaptors	P1035R7	Requires Xcode 15 or later
Views should not be required to be default constructible	P2325R3	Requires Xcode 15 or later
Smart pointer creation with default initialization	P1020R1	Requires Xcode 15 or later
Superior String Splitting	P2210R2	Requires Xcode 15 or later
basic_istream_view::iterator should not be copyable	P1638R1	Requires Xcode 15 or later
Output std::chrono::days with ‘d’ suffix	P1650R0	Requires Xcode 15 or later
Ranges adaptors for non-copyable iterators	P1862R1	Requires Xcode 15 or later
Rename “_default_init” Functions, Rev1	P1973R1	Requires Xcode 15 or later
elements_view needs its own sentinel	P1994R1	Requires Xcode 15 or later
Fix istream_view	P2432R1	Requires Xcode 15 or later
Making std::vector constexpr	P1004R2	Requires Xcode 14.3 or later
Consistent stateful allocator propagation for operator+(basic_string)	P1165R1	Requires Xcode 14.3 or later
Support arrays in make_shared and allocate_shared	P0674R1	Requires Xcode 14.3 or later
Making std::string constexpr	P0980R1	Requires Xcode 14.3 or later
Consider ATOMIC_FLAG_INIT undeprecation	LWG3659	Requires Xcode 14.3 or later
char8_t backward compatibility remediation	P1423R3	Requires Xcode 14.3 or later
Bit-casting object representations	P0476R2	Requires Xcode 14.3 or later
Ranges	P0896R4	Requires Xcode 14.3 or later
	P2415R2	Requires Xcode 14.3 or later
	P2281R1	Requires Xcode 14.3 or later
std::endian	P0463R1
Add constexpr modifiers to functions in <algorithm> and <utility> headers	P0202R3
Make std::memory_order a scoped enumeration	P0439R0
String prefix and suffix checking	P0457R2
Transformation trait remove_cvref	P0550R2
De-pessimize legacy <numeric> algorithms with std::move	P0616R0
Utility to convert a pointer to a raw pointer	P0653R2
Deprecate is_pod	P0767R1
Library support for the spaceship (comparison) operator <=>	P0768R1
Treating unnecessary decay	P0777R1
<span>	P0122R7
Thou shalt not specialize std function templates!	P0551R3
<version>	P0754R2
Comparing unordered containers	P0809R0
Constexpr iterator requirements	P0858R0
string::reserve should not shrink	P0966R1
Checking for existence of an element in associative containers	P0458R2
Guaranteed copy elision for piecewise construction	P0475R1
Integral power-of-2 operations	P0556R3
Reviewing deprecated facilities of C++17 for C++20	P0619R4	Not supported: P0619, Sections D.4, D.7, D.11, and D.12
Improving the return value of erase-like algorithms	P0646R1
Efficient sized delete for variable sized classes	P0722R3
Implicit conversion traits and utility functions	P0758R1
fpos requirements	P0759R1
Add shift to <algorithm>	P0769R2
constexpr for swap and swap related functions	P0879R0
The identity metafunction	P0887R1
Standard library concepts	P0898R3
Eradicating unnecessarily explicit default constructors	P0935R0
constexpr comparison operators for std::array	P1023R0
std::unwrap_ref_decay and std::unwrap_reference	P0318R1
Simplified partial function application	P0356R5
Supporting Incomplete types In reference_wrapper	P0357R3
Fixing operator>>(basic_istream&, CharT*)	P0487R1
std::is_constant_evaluated()	P0595R2
Variant and optional should propagate copy/move triviality	P0602R4
Improving variant’s Converting Constructor/Assignment	P0608R3
visit<R>: explicit return type for visit	P0655R1
std::function move constructor should be noexcept	P0771R1
Heterogeneous lookup for unordered containers	P0919R3
<chrono> zero(), min(), and max() should be noexcept	P0972R0
constexpr in std::pointer_traits	P1006R1
Misc constexpr bits	P1032R1
Remove comparison operators of std::span	P1085R2
Adopt consistent container erasure from library fundamentals 2	P1209R0
Remove CommonReference requirement from StrictWeakOrdering	P1248R1
Making std::underlying_type SFINAE-friendly	P0340R3
Well-behaved interpolation for numbers and pointers	P0811R3
Usability enhancements for std::span	P1024R3
Make create_directory() intuitive	P1164R1
signed ssize() functions, unsigned size() functions	P1227R2
Traits for [Un]bounded Arrays	P1357R1
Mandating the standard library: Clause 16 - Language support library	P1458R1
Mandating the standard library Clause 18 - Diagnostics library	P1459R1
Mandating the standard library: Clause 20 - Strings library	P1462R1
Mandating the standard library: Clause 22 - Iterators library	P1464R1
to_array from LFTS with updates	P0325R4
Bit operations	P0553R4
Math constants	P0631R8
More onstexpr containers	P0784R7
constexpr invoke	P1065R2
Synchronization library (<barrier>, <latch>, <semaphore> and notification functions on std::atomic)	P1135R6	Minimum deployment target: macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0
Exposing a narrow contract for ceil2	P1355R2
Relocate endian’s specification	P1612R1
bind_front should not unwrap reference_wrapper	P1651R0
Remove dedicated precalculated hash lookup interface	P1661R1
Fixing atomic initialization	P0883R2
Range constructor for std::string_view	P1391R4
Range constructor for std::span	P1394R4
constexpr for numeric algorithms	P1645R1
Heterogeneous lookup for unordered containers	P1690R1
Add max() to latch and barrier	P1865R1	Minimum deployment target: macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0
Concept traits should be named after concepts	P1871R1
span should have size_type, not index_type	P1872R0
Remove std::weak_equality and std::strong_equality	P1959R0
Safe integral comparisons	P0586R2
Improving the return value of erase-like algorithms II: free erase/erase if	P1115R3
On the names of low-level bit manipulation functions	P1956R1
Wording for boolean-testable	P1964R2
Fixed-size span construction from dynamic range	P1976R2
Remove tuple-like protocol support from fixed-extent span	P2116R0
Missing constexpr in std::optional and std::variant	P2231R1	Not supported: changes to std::variant

C++17

Feature	Paper	Notes
static_assert with no message	N3928
Removing trigraphs	N4086
typename in a template template parameter	N4051
New auto rules for direct-list-initialization	N3922
Fold expressions	N4295
	P0036R0
u8 character literals	P0036R0
Nested namespace definition	N4230
Attributes for namespaces and enumerators	N4266
Allow constant evaluation for all non-type template arguments	N4268
Remove deprecated register storage class	P0001R1
Remove deprecated bool increment	P0002R1
Make exception specifications part of the type system	P0012R1
__has_include in preprocessor conditionals	P0061R1
[[fallthrough]] attribute	P0188R1
[[nodiscard]] attribute	P0189R1
	P1771R1 (DR)
[[maybe_unused]] attribute	P0212R1
Aggregate initialization of classes with base classes	P0017R1
constexpr lambda expressions	P0170R1
Differing begin and end types in range-based for	P0184R0
Lambda capture of *this	P0018R3
Direct-list-initialization of enums	P0138R2
Hexadecimal floating-point literals	P0245R1
Using attribute namespaces without repetition	P0028R4
Dynamic memory allocation for over-aligned data	P0035R4
Template argument deduction for class templates	P0091R3
	P0512R0
	P0620R0 (DR)
	P0702R1 (DR)
Non-type template parameters with auto type	P0127R2
Guaranteed copy elision	P0135R1
Stricter expression evaluation order	P0145R3
	P0400R0
Requirement to ignore unknown attributes	P0283R2
constexpr if statements	P0292R2
Inline variables	P0386R2
Structured bindings	P0217R3
	P0961R1 (DR)
	P0969R0 (DR)
Separate variable and condition for if and switch	P0305R1
Matching of template template-parameters to arguments	P0522R0	This feature can be source breaking. Should be enabled explicitly with the compiler flag -frelaxed-template-template-args
Removing deprecated dynamic exception specifications	P0003R5
Features implemented in the libc++library
<memory_resource>	P0220R1	Requires Xcode 15 Minimum deployment target: iOS 17.0, macOS 14.0, watchOS 10.0 and tvOS 17.0.
Filesystem library	P0219R1	Minimum deployment target: macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0
	P0218R1
	P0392R0
	P0317R1
	P0492R2
TransformationTrait Alias void_t.	N3911
Invoke function template	N4169
std::uncaught_exceptions	N4259
TriviallyCopyable reference_wrapper.	N4277
Improved insertion interface for unique-key maps.	N4279
std::size(), std::empty() and std::data()	N4280
Contiguous Iterators	N4284
Cleanup for exception-specification and throw-expression.	N4285
Improving std::pair and std::tuple	N4387
bool_constant	N4389
shared_mutex	N4508	Pass -fno-exceptions compiler flag to back deploy to older OSes. Note that methods that throw exceptions on failure will abort in this mode.
LWG 2228 missing SFINAE rule	N4366
Minimal incomplete type support for standard containers	N4510
Remove deprecated iostreams aliases.	P0004R1
Adopt type traits variable templates for C++17	P0006R0
Polishing <chrono>	P0092R1
Constant view: std::as_const helper function template.	P0007R1
Making std::owner_less more flexible	P0074R0
Logical type traits rev 2	P0013R1
Re-enabling shared_from_this	P0033R1
Adopt not_fn from library fundamentals 2 for C++17	P0005R4
constexpr atomic::is_always_lock_free	P0152R1
[nothrow-]swappable traits	P0185R1
Fixing a design mistake in the searchers interface	P0253R1
An algorithm to clamp a value between a pair of boundary values	P0025R0
3-argument overload to std::hypot	P0030R1
Constexpr modifiers for reverse_iterator, move_iterator, array and Range Access	P0031R0
Give std::string a non-const .data() member function	P0272R1
is_callable, the missing INVOKE related trait	P0077R2
Homogeneous interface for variant, any and optional	P0032R3
Extending memory management tools	P0040R3
C++17 should refer to C11 instead of C99	P0063R3
Splicing maps and sets	P0083R3
Emplace return type	P0084R2
Variant: a type-safe union for C++17	P0088R3	Minimum deployment target: bad_variant_access and methods that throw it: get and visit require macOS 10.13, iOS 11.0, tvOS 11.0, watchOS 4.0 Pass -fno-exceptions compiler flag to back deploy to older OSes. Note that methods that throw exceptions on failure will abort in this mode.
Replacement of class objects containing reference members	P0137R1
shared_ptr::weak_type	P0163R0
Synopses for the c library	P0175R1
Reserve a new library namespace for future standardization	P0180R2
make_from_tuple: apply for construction	P0209R2
Integrating std::string_view and std::string	P0254R2
has_unique_object_representations	P0258R2
Adopt selected library fundamentals V2 components for C++17	P0295R0
Adopt library fundamentals V1 TS components for C++17 (optional, string_view, any)	P0220R1	Minimum deployment target: bad_optional_access and bad_any_cast, and methods that throw them: optional::value and any_cast require macOS 10.13, iOS 12.0, tvOS 12.0, watchOS 5.0 Pass -fno-exceptions compiler flag to back deploy to older OSes. Note that methods that throw exceptions on failure will abort in this mode.
Removing allocator support in std::function	P0302R1
Making optional greater equal again	P0307R2
Better names for parallel execution policies in C++17	P0336R1
Delete operator= for polymorphic_allocator	P0337R0
A <random> nomenclature tweak	P0346R1
Fixes for not_fn	P0358R1
Temporarily discourage memory_order_consume	P0371R1
Making variant greater equal	P0393R3
Removing deprecated exception specifications from C++17	P0003R5
Elementary string conversions std::to_chars, std::from_chars	P0067R5	Minimum deployment target: For integral types, macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0 For floating-point types, macOS 13.3, iOS 16.3, tvOS 16.3, watchOS 9.3
Literal suffixes for basic_string_view	P0403R1
Merging shared_ptr changes from Library Fundamentals to C++17	P0414R2
Constexpr for std::char_traits	P0426R1
Resolving LWG Issues re common_type	P0435R1
Correcting library usage of “literal type”	P0503R0
Revisiting in-place tag types for any/optional/variant	P0504R0
Wording for GB 50 - constexpr for chrono	P0505R0
Updating “Restrictions on exception handling”	P0509R1
Disallowing references, incomplete types, arrays, and empty variants	P0510R0
Poisoning the hash	P0513R0
Clarify that shared_future’s copy operations have wide contracts	P0516R0
Make future_error constructible	P0517R0
shared_ptr use_count/unique	P0521R0
Variadic lock guard(rev 5)	P0156R2
A byte type definition	P0298R3
File system library on non-POSIX-like operating systems	P0430R2
Integrating template deduction for class templates into the standard library	P0433R2
common_type and duration	P0548R1
Resolving atomic<T> named base class inconsistencies	P0558R1
noexcept for hash functions	P0599R1
Resolving GB 55, US 84, US 85, US 86	P0604R0
Some improvements to class template argument deduction integration into the standard library	P0739R0

C++14

Feature	Paper	Notes
Tweak to certain c++ contextual conversions	N3323
Binary literals	N3472
decltype(auto)	N3638
Return type deduction for normal functions
Initialized lambda captures	N3648
Generic lambdas	N3649
Variable templates	N3651
Relaxing requirements on constexpr functions	N3652
Member initializers and aggregates	N3653
Clarifying memory allocation	N3664
[[deprecated]] attribute	N3760
Single quotation mark as digit separator	N3781
Sized deallocation (delete and delete[])	N3778
Features implemented in the libc++library
Terminology for container element requirements - Rev 1	N3346
Making operator functors greater<>	N3421
std::result_of and SFINAE	N3462
integral_constant improvements	N3545
Null forward iterators	N3644
std::exchange()	N3668
Compile-time integer sequences	N3658
Addressing tuples by type	N3670
Making non-modifying sequence operations more robust	N3671
make_unique	N3656
Quoted Strings	N3654
User-defined Literals	N3642
TransformationTraits Redux (excluding part 4)	N3655
Heterogeneous comparison lookup	N3657
Fixing constexpr member functions without const	N3669
Shared locking	N3659
User-defined literals for std::complex	N3779
Discouraging rand()	N3924
Consistent metafunction aliases	N3887
Rename shared_mutex to shared_timed_mutex	N3891
Constexpr library additions: chrono, containers, utilities, complex numbers, functional	N3469
	N3470
	N3471
	N3302
	N3789

C++11

Feature	Paper	Notes
Rvalue references	N2118
	P1825R0 (DR)
Rvalue references for *this	N2439
Initialization of class objects by rvalues	N1610
Non-static data member initializers	N2756
Variadic templates	N2242
Extending variadic template template parameters	N2555
Initializer lists	N2672
	P1009R2 (DR)
	P1957R2 (DR)
Static assertions	N1720
auto-typed variables	N1984
Multi-declarator auto	N1737
Removal of auto as a storage-class specifier	N2546
New function declarator syntax	N2541
Declared type of an expression	N2343
Incomplete return types	N3276
Right angle brackets	N1757
Default template arguments for function templates	DR226
Solving the SFINAE problem for expressions	DR339
Alias templates	N2258
Extern templates	N1987
Null pointer constant	N2431
Strongly-typed enums	N2347
Forward declarations for enums	N2764
	DR1206
Standardized attribute syntax	N2761
ConstExpr: generalized constant expressions	N2235
	P0859R0 (DR)
Alignment support	N2341
Conditionally-support behavior	N1627
Changing undefined behavior into diagnosable errors	N1727
Delegating constructors	N1986
Inheriting constructors	N2540
	P0136R1 (DR)
Explicit conversion operators	N2437
New character types	N2249
Unicode string literals	N2442
Raw string literals	N2442
Universal character names in literals	N2170
User-defined literals	N2765
Standard Layout Types	N2342
Defaulted functions	N2346
	P1286R2 (DR)
Deleted functions	N2346
Extended friend declarations	N1791
Extending sizeof	N2253
	DR850
Inline namespaces	N2535
Unrestricted unions	N2544
Local and unnamed types as template arguments	N2657
Range-based for	N2930
	P0962R1 (DR)
Explicit virtual overrides	N2928
	N3206
	N3272
Allowing move constructors to throw [noexcept]	N3050
Defining move special member functions	N3053
Concurrency
Sequence points	N2239
Atomic operations	N2427
Strong compare and exchange	N2748
Bidirectional fences	N2752
Memory model	N2429
Data-dependency ordering: atomics and memory model	N2664
Propagating exceptions	N2179
Allow atomics use in signal handlers	N2547
Thread-local storage	N2659
Dynamic initialization and destruction with concurrency	N2660
C99 Features in C++11
__func__ predefined identifier	N2340
C99 preprocessor	N1653
long long	N1811

C++98/03

Clang and libc++ supports all features of the ISO C++ 1998 standard and the defects addressed in the ISO C++ 2003 standard.

C++ standard library hardening

Starting in Xcode 16, the C++ standard library supports hardening. Turning on hardening enables checks for common cases of misuse of the standard library; if a check fails, the program is reliably terminated, helping prevent security vulnerabilities and diagnose some cases of undefined behavior.

Hardening can be turned on via Xcode Build Settings (Apple Clang - Language - C++ > Enable C++ Standard Library Hardening):

• “No” — don’t enable any hardening checks.
• “Yes (fast)” — enable low-overhead security-critical checks at runtime. We recommend most applications to adopt this setting in the production environment.
• “Yes (extensive)” — enable all available low-overhead checks at runtime, including general logic errors in addition to security vulnerabilities. This setting has a higher overhead compared to “Yes” but is still intended to be usable in production by applications that would benefit from the increased level of correctness checking.
• “Yes (debug)” — enable all available checks, including heuristic checks that might have significant performance overhead, as well as internal library assertions. We recommend most applications to use this setting in non-production environments (such as test suites and CI, as well as for local development). This setting should not be used in production due to the overhead.

Note that the Debug configuration enables debug hardening mode by default. When enabling hardening, make sure not to accidentally override the stricter debug mode with a less-strict production-capable mode in the Debug configuration. Turning on hardening might expose latent bugs and cause the application to terminate at runtime. We recommend testing your code thoroughly in a development environment.

For more information about hardening, refer to the libc++ documentation.

Related resources

Videos

• • Mix Swift and C++
  • Simplify C++ templates with concepts from WWDC22
  • What’s New in Clang and LLVM from WWDC19

Release notes and documentation

• • Xcode 15.3 Release Notes
  • Using C++ APIs in Swift and Swift APIs in C++
  • Xcode 15 Release Notes (Apple Clang and libc++)
  • Xcode 14.3 Release Notes (Apple Clang and libc++)
  • Getting started with Metal-cpp
• Older release notes:
  • MacOS Monterey 12.3 Release Notes (libc++)
  • Xcode 14 Release Notes (Apple Clang)