C++ Support in Clang

Clang implements the following published and upcoming ISO C++ standards:

Language Standard	Flag	Available in Clang?
C++2c	`-std=c++2c`	Partial
C++23	`-std=c++23`	Partial
C++20	`-std=c++20`	Partial
C++17	`-std=c++17`	Clang 5
C++14	`-std=c++14`	Clang 3.4
C++11	`-std=c++11`	Clang 3.3
C++98 / C++03	`-std=c++98`	Yes (other than `export`)

The Clang community is continually striving to improve C++ standards compliance between releases by submitting and tracking C++ Defect Reports and implementing resolutions as they become available.

Experimental work is also under way to implement C++ Technical Specifications that will help drive the future of the C++ programming language.

The LLVM bug tracker uses the "c++" label, as well as mode-specific labels such as "c++11", "c++14", and so on, to track known bugs with Clang's language conformance.

C++2c implementation status

Clang has support for some of the features of the C++ standard following C++23, informally referred to as C++26.

You can use Clang in C++2c mode with the -std=c++2c option.

List of features and minimum Clang version with support

Language Feature	C++26 Proposal	Available in Clang?
Remove undefined behavior from lexing	P2621R2 (DR)	Clang 3.3
Making non-encodable string literals ill-formed	P1854R4 (DR)	Clang 14
Unevaluated strings	P2361R6	Clang 18
Add @, $, and ` to the basic character set	P2558R2	Yes
constexpr cast from `void*`	P2738R1	Clang 17
On the ignorability of standard attributes	P2552R3 (DR)	Yes
Static storage for braced initializers	P2752R3 (DR)	No
User-generated `static_assert` messages	P2741R3	Clang 17
Placeholder variables with no name	P2169R4	Clang 18
Template parameter initialization	P2308R1 (DR)	Clang 18
Pack Indexing	P2662R3	Clang 19
Remove Deprecated Arithmetic Conversion on Enumerations	P2864R2	Clang 18
Disallow Binding a Returned Glvalue to a Temporary	P2748R5	Clang 19
Clarifying rules for brace elision in aggregate initialization	P3106R1 (DR)	Clang 17
Attributes for Structured Bindings	P0609R3	Clang 19
Module Declarations Shouldn’t be Macros	P3034R1 (DR)	No
Trivial infinite loops are not Undefined Behavior	P2809R3 (DR)	Clang 19
Erroneous behaviour for uninitialized reads	P2795R5	No
`= delete("should have a reason");`	P2573R2	Clang 19
Variadic friends	P2893R3	Clang 20
`constexpr` placement new	P2747R2	Clang 20
Deleting a Pointer to an Incomplete Type Should be Ill-formed	P3144R2	Clang 19
Ordering of constraints involving fold expressions	P2963R3	Clang 19
Structured binding declaration as a condition	P0963R3	Clang 21
constexpr structured bindings	P2686R5	No
Allowing exception throwing in constant-evaluation	P3068R6	No
Remove Deprecated Array Comparisons from C++26	P2865R6	Clang 20
Structured Bindings can introduce a Pack	P1061R10	Clang 21
The Oxford variadic comma	P3176R1	Clang 20
Trivial unions	P3074R7	No
Partial program correctness	P1494R5	No
Contracts	P2900R14	No
Defang and deprecate `memory_order::consume`	P3475R2	No
Concept and variable-template template-parameters	P2841R7	No
Trivial Relocatability	P2786R13	No
#embed	P1967R14	No

C++23 implementation status

Clang has support for some of the features of the ISO C++ 2023 standard.

You can use Clang in C++23 mode with the -std=c++23 option.

List of features and minimum Clang version with support

Language Feature	C++23 Proposal	Available in Clang?
Literal suffix `uz`, `z` for `size_t`, `ssize_t`	P0330R8	Clang 13
Make `()` in lambdas optional in all cases	P1102R2	Clang 13
Simpler implicit move	P2266R3	Clang 13
`if consteval`	P1938R3	Clang 14
Allow duplicate attributes	P2156R1 (DR)	Clang 13
Narrowing contextual conversions to bool	P1401R5	Clang 14
Trimming whitespaces before line splicing	P2223R2	Yes
Make declaration order layout mandated	P1874R4	Yes
C++ identifier syntax using UAX 31	P1949R7 (DR)	Clang 14
Mixed string literal concatenation	P2201R1	Yes
Deducing this	P0847R7	Clang 18
Deducing this	P2797R0	Clang 19
Change scope of lambda trailing-return-type	P2036R3 (DR)	Clang 17
Change scope of lambda trailing-return-type	P2579R0 (DR)	Clang 17
Multidimensional subscript operator	P2128R6	Clang 15
Non-literal variables (and labels and gotos) in constexpr functions	P2242R3	Clang 15
Character encoding of diagnostic text	P2246R1	Yes
Character sets and encodings	P2314R4	Yes
Consistent character literal encoding	P2316R2	Yes
Add support for preprocessing directives elifdef and elifndef	P2334R1	Clang 13
Extend init-statement to allow alias-declaration	P2360R0	Clang 14
auto(x): decay-copy in the language	P0849R8	Clang 15
Attributes on Lambda-Expressions	P2173R1	Clang 13
`constexpr` for `<cmath>` and `<cstdlib>`	P0533R9	No
Type trait to determine if a reference binds to a temporary	P2255R2	Clang 19
The Equality Operator You Are Looking For	P2468R2 (DR)	Clang 16
De-deprecating volatile compound operations	P2327R1 (DR)	Clang 15
Support for `#warning`	P2437R1	Yes
Remove non-encodable wide character literals and multicharacter wide character literals	P2362R3	Clang 14
Labels at the end of compound statements	P2324R2	Clang 16
Delimited escape sequences	P2290R3	Clang 15
Named universal character escapes	P2071R2	Clang 15
Relaxing some constexpr restrictions	P2448R2	Clang 19
Using unknown pointers and references in constant expressions	P2280R4 (DR)	Clang 20
static `operator()`	P1169R4	Clang 16
Extended floating-point types and standard names	P1467R9	No
Class template argument deduction from inherited constructors	P2582R1	No
Portable assumptions	P1774R8	Clang 19
Support for UTF-8 as a portable source file encoding	P2295R6	Clang 15
`char8_t` Compatibility and Portability Fix	P2513R3 (DR)	Clang 16
Relax requirements on `wchar_t` to match existing practices	P2460R2 (DR)	Yes
Explicit lifetime management	P2590R2	No
static `operator[]`	P2589R1	Clang 16
Permitting static constexpr variables in constexpr functions	P2647R1	Clang 16
consteval needs to propagate up	P2564R3 (DR)	Clang 17
Lifetime extension in range-based for loops	P2718R0	Clang 20
Referencing The Unicode Standard	P2736R2	Yes

C++20 implementation status

Clang has support for some of the features of the ISO C++ 2020 standard.

You can use Clang in C++20 mode with the -std=c++20 option (use -std=c++2a in Clang 9 and earlier).

List of features and minimum Clang version with support

Language Feature	C++20 Proposal	Available in Clang?
Default member initializers for bit-fields	P0683R1	Clang 6
`const&`-qualified pointers to members	P0704R1	Clang 6
Allow lambda-capture`[=, this]`	P0409R2	Clang 6
`__VA_OPT__` for preprocessor comma elision	P0306R4	Clang 6
`__VA_OPT__` for preprocessor comma elision	P1042R1	Clang 9
Designated initializers	P0329R4	Clang 10
template-parameter-list for generic lambdas	P0428R2	Clang 9
Concepts	P0734R0	Clang 10
	P0857R0	Clang 16
	P1084R2	Clang 10
	P1141R2	Clang 10
	P0848R3	Clang 19
	P1616R1	Clang 10
	P1452R2	Clang 10
	P1972R0	Clang 10
	P1980R0
	P2103R0
	P2493R0 (DR)
	P2092R0	Clang 16
	P2113R0	Clang 16
Range-based for statements with initializer	P0614R1	Clang 8
ADL and function templates that are not visible	P0846R0	Clang 9
`const` mismatch with defaulted copy constructor	P0641R2	Clang 8
Consistent comparison (`operator<=>`)	P0515R3	Clang 10
	P0905R1
	P1120R0
	P1185R2
	P1186R3
	P1630R1
	P1946R0
	P1959R0
	P2002R1	Clang 17
	P2085R0	Clang 14
Access checking on specializations	P0692R1	Clang 14
Default constructible and assignable stateless lambdas	P0624R2	Clang 8
Lambdas in unevaluated contexts	P0315R4	Clang 17
`[[no_unique_address]]` attribute	P0840R2	Clang 9
`[[likely]]` and `[[unlikely]]` attributes	P0479R5	Clang 12
`typename` optional in more contexts	P0634R3	Clang 16
Pack expansion in lambda init-capture	P0780R2	Clang 9
Class types as non-type template parameters	P0732R2	Clang 12
Generalized non-type template parameters of scalar type	P1907R1	Clang 18 (Partial) Reference type template arguments referring to instantiation-dependent objects and subobjects (i.e. declared inside a template but neither type- nor value-dependent) aren't fully supported.
Destroying operator delete	P0722R3	Clang 6
Relaxations of `constexpr` restrictions	P1064R0	Clang 9
	P1002R1	Clang 8
	P1327R1	Clang 9
	P1330R0	Clang 9
	P1331R2	Clang 10
	P1668R1
	P0784R7
Prohibit aggregates with user-declared constructors	P1008R1	Clang 8
Feature test macros	P0941R2	(see below)
`explicit(bool)`	P0892R2	Clang 9
Signed integers are two's complement	P1236R1	Clang 9
`char8_t`	P0482R6	Clang 7 (11)
Immediate functions (`consteval`)	P1073R3	Clang 17
Immediate functions (`consteval`)	P1937R2	Clang 14
`std::is_constant_evaluated`	P0595R2	Clang 9
Nested inline namespaces	P1094R2	Clang 8
Structured binding extensions	P1091R3	Clang 16
Structured binding extensions	P1381R1	Clang 16
Stronger Unicode requirements	P1041R4	Yes
Stronger Unicode requirements	P1139R2	Yes
Parenthesized initialization of aggregates	P0960R3	Clang 16
Parenthesized initialization of aggregates	P1975R0	Clang 16
Modules	P1103R3	Clang 15
	P1766R1 (DR)	Clang 11
	P1811R0	No
	P1703R1	Subsumed by P1857
	P1874R1	Clang 15
	P1979R0	No
	P1779R3	Clang 15
	P1857R3	No
	P2115R0	Partial
	P1815R2	Partial
	P2615R1 (DR)	No
	P2788R0 (DR)	No
Coroutines	P0912R5	Partial Fully supported on all targets except Windows, which still has some stability and ABI issues.
Deprecate `a[b,c]`	P1161R3	Clang 9
Deprecate some problematic uses of `volatile`	P1152R4	Clang 10
`[[nodiscard("with reason")]]`	P1301R4	Clang 9
`using enum`	P1099R5	Clang 13
Class template argument deduction for aggregates	P1816R0	Clang 17
Class template argument deduction for aggregates	P2082R1	Clang 17
Class template argument deduction for alias templates	P1814R0	Clang 19 (Partial) This feature has been initially completed, but the feature macro __cpp_deduction_guides has not been updated.
Permit conversions to arrays of unknown bound	P0388R4	Clang 14
`constinit`	P1143R2	Clang 10
Pseudo-destructors end object lifetimes	P0593R6 (DR)	Clang 11
More implicit moves	P1825R0 (DR)	Clang 13

(11): Prior to Clang 8, this feature is not enabled by -std=c++20, but can be enabled with -fchar8_t.

C++17 implementation status

Clang 5 and later implement all the features of the ISO C++ 2017 standard.

By default, Clang 16 or later builds C++ code according to the C++17 standard. You can use Clang in C++17 mode with the -std=c++17 option (use -std=c++1z in Clang 4 and earlier).

List of features and minimum Clang version with support

Language Feature	C++17 Proposal	Available in Clang?
`static_assert` with no message	N3928	Clang 3.5
Disabling trigraph expansion by default	N4086	Clang 3.5
`typename` in a template template parameter	N4051	Clang 3.5
New `auto` rules for direct-list-initialization	N3922	Clang 3.8 (8)
Fold expressions	N4295	Clang 3.6
Fold expressions	P0036R0	Clang 3.9
`u8` character literals	N4267	Clang 3.6
Nested namespace definition	N4230	Clang 3.6
Attributes for namespaces and enumerators	N4266	Clang 3.6
Allow constant evaluation for all non-type template arguments	N4268	Clang 3.6
Remove deprecated `register` storage class	P0001R1	Clang 3.8
Remove deprecated `bool` increment	P0002R1	Clang 3.8
Make exception specifications part of the type system	P0012R1	Clang 4
`__has_include` in preprocessor conditionals	P0061R1	Yes
`[[fallthrough]]` attribute	P0188R1	Clang 3.9
`[[nodiscard]]` attribute	P0189R1	Clang 3.9
`[[nodiscard]]` attribute	P1771R1 (DR)	Clang 9
`[[maybe_unused]]` attribute	P0212R1	Clang 3.9
Aggregate initialization of classes with base classes	P0017R1	Clang 3.9
`constexpr` lambda expressions	P0170R1	Clang 5
Differing `begin` and `end` types in range-based `for`	P0184R0	Clang 3.9
Lambda capture of `*this`	P0018R3	Clang 3.9
Direct-list-initialization of `enum`s	P0138R2	Clang 3.9
Hexadecimal floating-point literals	P0245R1	Yes
Using attribute namespaces without repetition	P0028R4	Clang 3.9
Dynamic memory allocation for over-aligned data	P0035R4	Clang 4
Template argument deduction for class templates	P0091R3	Clang 5
	P0512R0	Clang 5
	P0620R0 (DR)	Clang 7
	P0702R1 (DR)	Clang 6
Non-type template parameters with `auto` type	P0127R2	Clang 4
Guaranteed copy elision	P0135R1	Clang 4
Stricter expression evaluation order	P0145R3	Clang 4 (9)
Stricter expression evaluation order	P0400R0	Clang 4 (9)
Requirement to ignore unknown attributes	P0283R2	Yes
`constexpr`if-statements	P0292R2	Clang 3.9
Inline variables	P0386R2	Clang 3.9
Structured bindings	P0217R3	Clang 4
	P0961R1 (DR)	Clang 8
	P0969R0 (DR)	Clang 8
Separate variable and condition for `if` and `switch`	P0305R1	Clang 3.9
Matching template template parameters to compatible arguments	P0522R0 (DR)	Clang 19 (10)
Removing deprecated dynamic exception specifications	P0003R5	Clang 4
Pack expansions in using-declarations	P0195R2	Clang 4

(8): This is a backwards-incompatible change that is applied to all language versions that allow type deduction from auto (per the request of the C++ committee). In Clang 3.7, a warning is emitted for all cases that would change meaning.
(9): Under the MS ABI, function parameters are destroyed from left to right in the callee. As a result, function parameters in calls to operator<<, operator>>, operator->*, operator&&, operator||, and operator, functions using expression syntax are no longer guaranteed to be destroyed in reverse construction order in that ABI. This is not fully supported during constant expression evaluation until Clang 12.
(10): While this feature was initially implemented in Clang 4, it was not enabled by default prior to clang 19, but could be enabled with -frelaxed-template-template-args. In Clang 19, the flag was deprecated. In Clang 21, the flag was removed altogether.

C++14 implementation status

Clang 3.4 and later implement all of the ISO C++ 2014 standard.

You can use Clang in C++14 mode with the -std=c++14 option (use -std=c++1y in Clang 3.4 and earlier).

List of features and minimum Clang version with support

Language Feature	C++14 Proposal	Available in Clang?
Tweak to certain C++ contextual conversions	N3323	Clang 3.4
Binary literals	N3472	Clang 2.9
decltype(auto)	N3638	Clang 3.3
Return type deduction for normal functions	N3638	Clang 3.4
Initialized lambda captures	N3648	Clang 3.4
Generic lambdas	N3649	Clang 3.4
Variable templates	N3651	Clang 3.4
Relaxing requirements on constexpr functions	N3652	Clang 3.4
Member initializers and aggregates	N3653	Clang 3.3
Clarifying memory allocation	N3664	Clang 3.4
`[[deprecated]]` attribute	N3760	Clang 3.4
Single quotation mark as digit separator	N3781	Clang 3.4
C++ Sized Deallocation	N3778	Clang 3.4 (7)

(7): The user must supply definitions of the sized deallocation functions, either by providing them explicitly or by using a C++ standard library that does. libstdc++ added these functions in version 5.0, and libc++ added them in version 3.7. The user can also use the -fno-sized-deallocation option to disable sized deallocation.

C++11 implementation status

Clang 3.3 and later implement all of the ISO C++ 2011 standard.

You can use Clang in C++11 mode with the -std=c++11 option. Clang's C++11 mode can be used with libc++ or with gcc's libstdc++.

List of features and minimum Clang version with support

Language Feature	C++11 Proposal	Available in Clang?
Rvalue references	N2118	Clang 2.9
Rvalue references	P1825R0 (DR)	Clang 13
Rvalue references for `*this`	N2439	Clang 2.9
Initialization of class objects by rvalues	N1610	Clang 2.9
Non-static data member initializers	N2756	Clang 3.0
Variadic templates	N2242	Clang 2.9
Extending variadic template template parameters	N2555	Clang 2.9
Initializer lists	N2672	Clang 3.1
	P1009R2 (DR)	Clang 9
	P1957R2 (DR)	Clang 11
Static assertions	N1720	Clang 2.9
`auto`-typed variables	N1984	Clang 2.9
Multi-declarator `auto`	N1737	Clang 2.9
Removal of auto as a storage-class specifier	N2546	Clang 2.9
New function declarator syntax	N2541	Clang 2.9
Lambda expressions	N2927	Clang 3.1
Lambda expressions	P0588R1 (DR)	No
Declared type of an expression	N2343	Clang 2.9
Incomplete return types	N3276	Clang 3.1
Right angle brackets	N1757	Clang 2.9
Default template arguments for function templates	DR226	Clang 2.9
Solving the SFINAE problem for expressions	DR339	Clang 2.9
Alias templates	N2258	Clang 3.0
Extern templates	N1987	Clang 2.9
Null pointer constant	N2431	Clang 3.0
Strongly-typed enums	N2347	Clang 2.9
Forward declarations for enums	N2764 DR1206	Clang 3.1
Standardized attribute syntax	N2761	Clang 3.3 (1)
Generalized constant expressions	N2235	Clang 3.1
Generalized constant expressions	P0859R0 (DR)	Clang 8
Alignment support	N2341	Clang 3.3
Conditionally-support behavior	N1627	Clang 2.9
Changing undefined behavior into diagnosable errors	N1727	Clang 2.9
Delegating constructors	N1986	Clang 3.0
Inheriting constructors	N2540	Clang 3.3
Inheriting constructors	P0136R1 (DR)	Clang 3.9
Explicit conversion operators	N2437	Clang 3.0
New character types	N2249	Clang 2.9
Unicode string literals	N2442	Clang 3.0
Raw string literals	N2442	Clang 3.0
Universal character names in literals	N2170	Clang 3.1
User-defined literals	N2765	Clang 3.1
Standard Layout Types	N2342	Clang 3.0
Defaulted functions	N2346	Clang 3.0
Defaulted functions	P1286R2 (DR)	Clang 9
Deleted functions	N2346	Clang 2.9
Extended friend declarations	N1791	Clang 2.9
Extending `sizeof`	N2253 DR850	Clang 3.1
Inline namespaces	N2535	Clang 2.9
Unrestricted unions	N2544	Clang 3.1
Local and unnamed types as template arguments	N2657	Clang 2.9
Range-based for	N2930	Clang 3.0
Range-based for	P0962R1 (DR)	Clang 8
Explicit virtual overrides	N2928 N3206 N3272	Clang 3.0
Minimal support for garbage collection and reachability-based leak detection	N2670	N/A (2)
Allowing move constructors to throw [noexcept]	N3050	Clang 3.0
Defining move special member functions	N3053	Clang 3.0
Concurrency
Sequence points	N2239	Clang 3.3
Atomic operations	N2427	Clang 3.1
Strong Compare and Exchange	N2748	Clang 3.1 (3)
Bidirectional Fences	N2752	Clang 3.1
Memory model	N2429	Clang 3.2
Data-dependency ordering: atomics and memory model	N2664	Clang 3.2 (4)
Propagating exceptions	N2179	Clang 2.9
Allow atomics use in signal handlers	N2547	Clang 3.1
Thread-local storage	N2659	Clang 3.3 (5)
Dynamic initialization and destruction with concurrency	N2660	Clang 2.9
C99 Features in C++11
`__func__` predefined identifier	N2340	Clang 2.9
C99 preprocessor	N1653	Clang 2.9
`long long`	N1811	Clang 2.9
Extended integral types	N1988	N/A (6)

(1): The [[carries_dependency]] attribute has no effect.
(2): No compiler changes are required for an implementation such as Clang that does not provide garbage collection.
(3): All compare-exchange operations are emitted as strong compare-exchanges.
(4): memory_order_consume is lowered to memory_order_acquire.
(5): thread_local support requires a C++ runtime library providing __cxa_thread_atexit, such as libc++abi 3.6 or later, or libsupc++ 4.8 or later.
(6): No compiler changes are required for an implementation such as Clang that does not provide any extended integer types. __int128 is not treated as an extended integer type, because changing intmax_t would be an ABI-incompatible change.

C++98 implementation status

Clang implements all of the ISO C++ 1998 standard (including the defects addressed in the ISO C++ 2003 standard) except for export (which was removed in C++11).

Defect reports

Clang generally aims to implement resolutions to Defect Reports (bug fixes against prior standards) retroactively, in all prior standard versions where the fix is meaningful. Significant Defect Report changes to language features after the publication of the relevant standard are marked (DR) in the above table.

Clang also has a test suite for conformance to resolutions for issues on the C++ core issues list, most of which are considered Defect Reports. Implementation status for C++ core issues based on that test suite is tracked on a separate page.

Technical specifications and standing documents

ISO C++ also publishes a number of documents describing additional language and library features that are not part of standard C++.

List of features and minimum Clang version with support

Document	Latest draft	Compiler flag	Available in Clang?
SD-6: SG10 feature test recommendations	SD-6	N/A	Clang 3.4 (N3745)
			Clang 3.6 (N4200)
			Clang 4 (P0096R3)
			Clang 5 (P0096R4)
			Clang 7 (P0096R5)
			Clang 9 (P1353R0)
			Clang 10 (P1902R1)
[TS] Concepts	P0121R0		Superseded by P0734R0
[TS] Coroutines	N4663	`-fcoroutines-ts -stdlib=libc++`	Clang 5
[TS] Coroutines	N4663	`-std=c++20 -stdlib=libc++`	Superseded by P0912R5
[TS] Library Fundamentals, Version 1 (invocation type traits)	N4480	N/A	No
[TS] Library Fundamentals, Version 2 (`source_location`)	N4617	N/A	Clang 9 (documentation)
[TS] Modules	N4720	`-fmodules-ts`	Superseded by P1103R3
[DRAFT TS] Reflection	N4818		No
[TS] Transactional Memory	N4514		No