# C++ and C++'0x Support in Clang

Last updated: $Date$

Clang currently implements all of the ISO C++ 1998 standard (including the defects addressed in the ISO C++ 2003 standard) except for 'export' (which has been removed from the C++'0x draft) and is considered a production-quality C++ compiler. The LLVM bug tracker contains a Clang C++ component that tracks known Clang C++ bugs.

## C++0x Implementation status

Clang provides support for a number of features included in the upcoming ISO C++ Standard, C++0x. This section tracks the status of various C++0x features, and a number of other C++0x features are under active development.

You can use Clang in C++0x mode either with libc++ or with gcc's libstdc++. libstdc++-4.4 requires a patch to work with clang; other versions have not been tested.

The following table is used to help track our implementation progress toward implementing the complete C++'0x standard. We use a simple, somewhat arbitrary color-coding scheme to describe the relative completeness of features:

Not started/not evaluated | Not Applicable | Broken | Some examples work | Many examples work | Nearly everything works | Complete
--- | --- | --- | --- | --- | --- | ---
| N/A |  |  |  |  | rXXXXXX

In addition, boxes marked with ✓ have complete and passing tests. Similarly, boxes marked with ✗ have complete tests, some of which are failing, and a ? indicates partial tests while not making any statement about passing status.

A feature is "complete" when the appropriate Clang component (Parse, AST, Sema, CodeGen) implements the behavior described in all of the paragraphs in the relevant C++'0x draft standard. The major components are:

Parse
  Clang is able to parse the grammar of this feature (or the grammar described by this section), but does not necessarily do anything with the parsed result. Use Clang's `-fsyntax-only` option to parse C++ programs.
AST
  Clang builds an abstract syntax tree (AST) for the feature, but does not necessarily perform any type-checking. Use Clang's `-ast-print` option to print the resulting ASTs.
Sema
  Clang parses and type-checks this feature and provides a well-formed AST annotated with types. Use Clang's `-fsyntax-only` to type-check code.
CodeGen
  Clang parses, type-checks, and generates code for this feature, allowing one to compile and execute programs.

Updates to this table are welcome! Tests for the various features are also welcome!

C++0x Features (current draft report here)
Feature | Parse | AST | Sema | CodeGen | Standard Sections | Notes
--- | --- | --- | --- | --- | --- | ---
Control Flow Modifications
Range-based for loop | ✓ | ✓ | ✓ | ✓ | 6.5.4 | N2243 N3271
Type System Modifications
rvalue references |  |  |  |  | 8.3.2 | N2118, N2831 N2439
decltype | ✓ | ✓ |  |  | 7.1.6.2 | N2343 N1478 N1978
auto type deduction | ✓ | ✓ | ✓ | ✓ | 7.1.6.2, 7.1.6.4 | N1984
nullptr |  |  |  |  | 2.14.7, 4.10, 4.11 | N2431 N1488 N2214
enum classes |  |  |  |  | 7.2 | N1513 N2347 N2499 Includes forward declaration capability
long long |  |  |  |  | 3.9.1 | C99 N1811
constexpr |  |  |  |  | 3.6.2, 3.9, 5.19, 7.1.5 | N1521 N2235
char16_t/char32_t |  |  |  |  |  | N2249
Unicode string literal types |  |  |  |  | 2.14.3, 2.14.5 |
Raw string literal types |  |  |  |  | 2.14.5 | N2053 N2442 N2378
user-defined literal types |  |  |  |  | 2.14.8 | N2378
POD definition changes |  |  |  |  | 3.9, 9 | N2294
Unrestricted unions |  |  |  |  | 9.5 | N2544
Tighter narrowing rules |  |  |  |  | 8.5.4 | N1890 N2215 N2640
Class Modifications
delegating constructors |  |  |  |  | 12.6.2 | N1986
inheriting constructors |  |  |  |  | 12.9 | N1890 N1898 N2512
In-declaration member initialization | ✓ | ✓ | ✓ | ✓ |  | N2628
Changes to implicitly generated methods |  |  |  |  |  | Includes implicit generation of move operations
defaulted methods |  |  |  |  |  | N1717 N2326
destructor defaults to noexcept |  |  |  |  |  |
sizeof on members without object instance |  |  |  |  |  | N2150
Explicit override controls | ✓ | ✓ | ✓ |  |  |
Explicit conversion operators | ✓ | ✓ | ✗ | N/A | 12.3 | N2437 N2333 Does not implement DR899
Template Modifications
Right angle brackets |  | N/A | N/A | N/A |  | N1757
variadic templates |  |  |  |  | 14.6.3 | N2080 N2087 N2242 N2488 N2555
template aliases | ✓ | ✓ | ✓ | ✓ | 7.1.3, 14.6.7 | N1489 N2258
Removal of export |  | N/A | N/A | N/A |  | This was never implemented in C++03
extern templates |  |  |  |  | 14.8.2 | N1987
Local classes as template parameters |  |  |  |  |  | N2402 N2657
Exception Modifications
Deprecation of exception specifications |  |  |  |  | 15.4 |
noexcept | ✓ | ✓ | ✓ | N/A | 5.3.7, 15.4 | N3050
Preprocessor Modifications
__STDC_HOSTED__ |  | N/A | N/A | N/A | 16.8 | C99 N1568
_Pragma |  | N/A | N/A | N/A | 16.9 | C99 N1568
Variable argument macros |  | N/A | N/A | N/A | 16.3 | C99 N1568
Empty macro arguments |  | N/A | N/A | N/A | 16.3 | C99 N1568
__func__ |  | N/A | N/A | N/A | 8.4.1 | C99 N1568
__cplusplus |  | N/A | N/A | N/A | 16.8 |
Things Completely New
Late-specified return type | ✓ | ✓ | ✓ | N/A | 8.3.5 | N2445
lambda expressions |  |  |  |  | 5.1.2 | N1968 N2550 N2859
Uniform initializers |  |  |  |  | 12.6 | N2215 N2640
Memory model |  |  |  |  | 1.7 | N2556
Miscellania
Standard attribute syntax |  |  |  |  |  | N2418
alignment control |  |  |  |  |  |
Deleted functions |  |  |  | N/A | 8.4.3 | N2326 This also includes class methods.
static_assert |  |  |  | N/A | 7 | N1381 N1720
Inline namespaces | ✓ | ✓ | ✓ | N/A | 7.3.1 | N2535
thread_local storage |  |  |  |  | 3.7.2, 7.1.1 | N2660
Standard Library Modifications, see libc++ or libstdc++ or VC++ 2010