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 | No |
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 | No |
The Oxford variadic comma | P3176R1 | Clang 20 |
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 |
P2797R0 | Clang 19 | |
Change scope of lambda trailing-return-type | P2036R3 (DR) | Clang 17 |
P2579R0 (DR) | ||
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) | No |
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 |
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 | ||
P0848R3 | Clang 19 | |
P1616R1 | Clang 10 | |
P1452R2 | ||
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 | ||
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 |
P1937R2 | Clang 14 | |
std::is_constant_evaluated | P0595R2 | Clang 9 |
Nested inline namespaces | P1094R2 | Clang 8 |
Structured binding extensions | P1091R3 | Clang 16 |
P1381R1 | ||
Stronger Unicode requirements | P1041R4 | Yes |
P1139R2 | ||
Parenthesized initialization of aggregates | P0960R3 | Clang 16 |
P1975R0 | ||
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 |
PartialFully 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 |
P2082R1 | ||
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 |
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 |
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 enums | 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 | ||
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) |
P0400R0 | ||
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.
Starting from Clang 19, the flag is deprecated and will be removed in a future
version.
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 | 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 |
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 |
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 |
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 |
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 |
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 |
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 |
-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 |