C++ Support in Clang
Last updated: $Date: 2014-06-22 09:00:05 -0700 (Sun, 22 Jun 2014) $
Clang fully implements all published ISO C++ standards including C++11, as well as the upcoming standard provisionally named C++14, and some parts of the fledgling C++1z standard, and is considered a production-quality C++ compiler.
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 contains Clang C++ components that track known bugs with Clang's language conformance in each language mode.
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).
C++11 implementation status
Clang 3.3 and later implement all of the ISO C++ 2011 standard. The following table describes the Clang version in which each feature became available.
By default, Clang builds C++ code according to the C++98 standard, with many
C++11 features accepted as extensions. 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++, but
patches are needed to make libstdc++-4.4
work with Clang in C++11 mode. Patches are also needed to make
libstdc++-4.6
and libstdc++-4.7 work with Clang
releases prior to version 3.2 in C++11 mode. thread_local support
currently requires the C++ runtime library from g++-4.8 or later.
| Language Feature | C++11 Proposal | Available in Clang? |
|---|---|---|
| Rvalue references | N2118 | Clang 2.9 |
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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 (5) |
(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): 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++1y implementation status
Clang 3.4 and later implement all of the Draft International Standard (see most recent publicly available draft) of the upcoming C++ language standard, provisionally named C++1y. The following table describes the Clang version in which each feature became available.
You can use Clang in C++1y mode with the -std=c++1y option.
| Language Feature | C++1y Proposal | Available in Clang? |
|---|---|---|
| Tweak to certain C++ contextual conversions | N3323 | Clang 3.4 |
| Binary literals | N3472 | Yes |
| 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 |
C++1z implementation status
Clang has highly experimental support for some proposed features of the C++ standard following C++1y, provisionally named C++1z. The following table describes which C++1z features have been implemented in Clang and in which Clang version they became available.
Note that support for these features may change or be removed without notice, as the draft C++1z standard evolves.
You can use Clang in C++1z mode with the -std=c++1z option.
| Language Feature | C++1z Proposal | Available in Clang? |
|---|---|---|
| static_assert with no message | N3928 | SVN |
| Disabling trigraph expansion by default | N3981 | SVN |
| Terse range-based for loops | N3994 | SVN |
| typename in a template template parameter | N4051 | SVN |
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++. The following table describes which language features have been implemented in Clang and in which Clang version they became available:
| Document | Latest draft | Available in Clang? |
|---|---|---|
| SD-6: SG10 feature test recommendations | SD-6 | Clang 3.4 (N3745) |
| [DRAFT TS] Array extensions (arrays of runtime bound) | N3820 | No |
| [DRAFT TS] Library fundamentals (invocation type traits) | N3908 | No |
| [DRAFT TS] Concepts | N3929 | No |