Keywords: ISO C++, library

Chapter 1. Status
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## Chapter 1. Status

## Implementation Status

### C++ 1998/2003

#### Implementation Status

This status table is based on the table of contents of ISO/IEC 14882:2003.

This section describes the C++ support in mainline GCC, not in any particular release.

Table 1.1. C++ 1998/2003 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
18 | Language support
18.1 | Types | Y |
18.2 | Implementation properties | Y |
18.2.1 | Numeric Limits |  |
18.2.1.1 | Class template `numeric_limits` | Y |
18.2.1.2 | `numeric_limits` members | Y |
18.2.1.3 | `float_round_style` | Y |
18.2.1.4 | `float_denorm_style` | Y |
18.2.1.5 | `numeric_limits` specializations | Y |
18.2.2 | C Library | Y |
18.3 | Start and termination | Y |
18.4 | Dynamic memory management | Y |
18.5 | Type identification |  |
18.5.1 | Class type_info | Y |
18.5.2 | Class bad_cast | Y |
18.5.3 | Class bad_typeid | Y |
18.6 | Exception handling |  |
18.6.1 | Class exception | Y |
18.6.2 | Violation exception-specifications | Y |
18.6.3 | Abnormal termination | Y |
18.6.4 | `uncaught_exception` | Y |
18.7 | Other runtime support | Y |
19 | Diagnostics
19.1 | Exception classes | Y |
19.2 | Assertions | Y |
19.3 | Error numbers | Y |
20 | General utilities
20.1 | Requirements | Y |
20.2 | Utility components |  |
20.2.1 | Operators | Y |
20.2.2 | `pair` | Y |
20.3 | Function objects |  |
20.3.1 | Base | Y |
20.3.2 | Arithmetic operation | Y |
20.3.3 | Comparisons | Y |
20.3.4 | Logical operations | Y |
20.3.5 | Negators | Y |
20.3.6 | Binders | Y |
20.3.7 | Adaptors for pointers to functions | Y |
20.3.8 | Adaptors for pointers to members | Y |
20.4 | Memory |  |
20.4.1 | The default allocator | Y |
20.4.2 | Raw storage iterator | Y |
20.4.3 | Temporary buffers | Y |
20.4.4 | Specialized algorithms | Y |
20.4.4.1 | `uninitialized_copy` | Y |
20.4.4.2 | `uninitialized_fill` | Y |
20.4.4.3 | `uninitialized_fill_n` | Y |
20.4.5 | Class template `auto_ptr` | Y |
20.4.6 | C library | Y |
21 | Strings
21.1 | Character traits |  |
21.1.1 | Character traits requirements | Y |
21.1.2 | traits typedef | Y |
21.1.3 | `char_traits` specializations |  |
21.1.3.1 | struct `char_traits<char>` | Y |
21.1.3.2 | struct `char_traits<wchar_t>` | Y |
21.2 | String classes | Y |
21.3 | Class template `basic_string` | Y |
21.4 | Null-terminated sequence utilities | Y | C library dependency
22 | Localization
22.1 | Locales |  |
22.1.1 | Class `locale` | Y |
22.1.2 | `locale` globals | Y |
22.1.3 | Convenience interfaces |  |
22.1.3.1 | Character classification | Y |
22.1.3.2 | Character conversions | Y |
22.2 | Standard locale categories |  |
22.2.1 | `ctype` | Y |
22.2.2 | Numeric |  |
22.2.2.1 | `num_get` | Y |
22.2.2.2 | `num_put` | Y |
22.2.3 | `num_punct` | Y |
22.2.4 | `collate` | Y |
22.2.5 | Time |  |
22.2.5.1 | `time_get` | Y |
22.2.5.2 | `time_get_byname` | Y |
22.2.5.3 | `time_put` | Y |
22.2.5.3 | `time_put_byname` | Y |
22.2.6 | Monetary |  |
22.2.6.1 | `money_get` | Y |
22.2.6.2 | `money_put` | Y |
22.2.6.3 | `money_punct` | Y |
22.2.6.4 | `money_punct_byname` | Y |
22.2.7 | `messages` | Y |
22.2.8 | Program-defined facets | Y |
22.3 | C Library Locales | Y |
23 | Containers
23.1 | Container requirements | Y |
23.2 | Sequence containers |  |
23.2.1 | Class template `deque` | Y |
23.2.2 | Class template `list` | Y |
23.2.3 | Adaptors |  |
23.2.3.1 | Class template `queue` | Y |
23.2.3.2 | Class template `priority_queue` | Y |
23.2.3.3 | Class template `stack` | Y |
23.2.4 | Class template `vector` | Y |
23.2.5 | Class `vector<bool>` | Y |
23.3 | Associative containers |  |
23.3.1 | Class template `map` | Y |
23.3.2 | Class template `multimap` | Y |
23.3.3 | Class template `set` | Y |
23.3.4 | Class template `multiset` | Y |
24 | Iterators
24.1 | Requirements | Y |
24.2 | Header `<iterator>` synopsis | Y |
24.3 | Iterator primitives | Y |
24.4 | Predefined iterators and Iterator adaptors |  |
24.4.1 | Reverse iterators | Y |
24.4.2 | Insert iterators | Y |
24.5 | Stream iterators |  |
24.5.1 | Class template `istream_iterator` | Y |
24.5.2 | Class template `ostream_iterator` | Y |
24.5.3 | Class template `istreambuf_iterator` | Y |
24.5.4 | Class template `ostreambuf_iterator` | Y |
25 | Algorithms
25.1 | Non-modifying sequence operations | Y |
25.2 | Mutating sequence operations | Y |
25.3 | Sorting and related operations | Y |
25.4 | C library algorithms | Y |
26 | Numerics
26.1 | Numeric type requirements | Y |
26.2 | Complex numbers | Y |
26.3 | Numeric arrays |  |
26.3.1 | Header `<valarray>` synopsis | Y |
26.3.2 | Class template `valarray` | Y |
26.3.3 | `valarray` non-member operations | Y |
26.3.4 | Class `slice` | Y |
26.3.5 | Class template `slice_array` | Y |
26.3.6 | Class `gslice` | Y |
26.3.7 | Class template `gslice_array` | Y |
26.3.8 | Class template `mask_array` | Y |
26.3.9 | Class template `indirect_array` | Y |
26.4 | Generalized numeric operations |  |
26.4.1 | `accumulate` | Y |
26.4.2 | `inner_product` | Y |
26.4.3 | `partial_sum` | Y |
26.4.4 | `adjacent_difference` | Y |
26.4.5 | iota | Y |
26.5 | C Library | Y |
27 | Input/output
27.1 | Requirements | Y |
27.2 | Forward declarations | Y |
27.3 | Standard iostream objects | Y |
27.3.1 | Narrow stream objects | Y |
27.3.2 | Wide stream objects | Y |
27.4 | Iostreams base classes | Y |
27.5 | Stream buffers | Y |
27.6 | Formatting and manipulators | Y |
27.7 | String-based streams | Y |
27.8 | File-based streams | Y |
Appendix D | Compatibility features
D.1 | Increment operator with bool operand |  |
D.2 | `static` keyword |  |
D.3 | Access declarations |  |
D.4 | Implicit conversion from const strings |  |
D.5 | C standard library headers |  |
D.6 | Old iostreams members |  |
D.7 | char* streams |  |

#### Implementation Specific Behavior

The ISO standard defines the following phrase:

> `[1.3.5] implementation-defined behavior`

>   Behavior, for a well-formed program construct and correct data, that depends on the implementation and that each implementation shall document.

We do so here, for the C++ library only. Behavior of the compiler, linker, runtime loader, and other elements of "the implementation" are documented elsewhere. Everything listed in Annex B, Implementation Qualities, are also part of the compiler, not the library.

For each entry, we give the section number of the standard, when applicable. This list is probably incomplet and inkorrekt.

1.9 [intro.execution]/11 #3 If `isatty(3)` is true, then interactive stream support is implied.

17.4.4.5 [lib.reentrancy] Non-reentrant functions are probably best discussed in the various sections on multithreading (see above).

18.1 [lib.support.types]/4 The type of `NULL` is described under Support.

18.3 [lib.support.start.term]/8 Even though it's listed in the library sections, libstdc++ has zero control over what the cleanup code hands back to the runtime loader. Talk to the compiler people. :-)

18.4.2.1 [lib.bad.alloc]/5 (bad_alloc), 18.5.2 [lib.bad.cast]/5 (bad_cast), 18.5.3 [lib.bad.typeid]/5 (bad_typeid), 18.6.1 [lib.exception]/8 (exception), 18.6.2.1 [lib.bad.exception]/5 (bad_exception): The `what()` member function of class `std::exception`, and these other classes publicly derived from it, returns the name of the class, e.g. `"std::bad_alloc"`.

18.5.1 [lib.type.info]/7 The return value of `std::type_info::name()` is the mangled type name. You will need to call `c++filt` and pass the names as command-line parameters to demangle them, or call a runtime demangler function.

20.1.5 [lib.allocator.requirements]/5 "Implementors are encouraged to supply libraries that can accept allocators that encapsulate more general memory models and that support non-equal instances. In such implementations, any requirements imposed on allocators by containers beyond those requirements that appear in Table 32, and the semantics of containers and algorithms when allocator instances compare non-equal, are implementation-defined." There is experimental support for non-equal allocators in the standard containers in C++98 mode. There are no additional requirements on allocators. It is undefined behaviour to swap two containers if their allocators are not equal.

21.1.3.1 [lib.char.traits.specializations.char]/3,4, 21.1.3.2 [lib.char.traits.specializations.wchar.t]/2, 21.3 [lib.basic.string]/6 basic_string::iterator, basic_string::const_iterator, 23.* [lib.containers]'s foo::iterator, 27.* [lib.input.output]'s foo::*_type, others... Nope, these types are called implementation-defined because you shouldn't be taking advantage of their underlying types. Listing them here would defeat the purpose. :-)

21.1.3.1 [lib.char.traits.specializations.char]/5 I don't really know about the mbstate_t stuff... see the `codecvt` notes for what does exist.

22.* [lib.localization] Anything and everything we have on locale implementation will be described under Localization.

23.* [lib.containers] All of the containers in this clause define size_type as std::size_t and difference_type as std::ptrdiff_t.

26.2.8 [lib.complex.transcendentals/9 I have no idea what `complex<T>`'s `pow(0,0)` returns.

27.4.2.4 [lib.ios.members.static/2 Calling `std::ios_base::sync_with_stdio` after I/O has already been performed on the standard stream objects will flush the buffers, and destroy and recreate the underlying buffer instances. Whether or not the previously-written I/O is destroyed in this process depends mostly on the `--enable-libio` choice: for stdio, if the written data is already in the stdio buffer, the data may be completely safe!

27.6.1.1.2 [lib.istream::sentry], 27.6.2.3 [lib.ostream::sentry] The I/O sentry ctor and dtor can perform additional work than the minimum required. We are not currently taking advantage of this yet.

27.7.1.3 [lib.stringbuf.virtuals]/16, 27.8.1.4 [lib.filebuf.virtuals]/10 The effects of `pubsetbuf/setbuf` are described in the Input and Output chapter.

27.8.1.4 [lib.filebuf.virtuals]/16 Calling `fstream::sync` when a get area exists will... whatever `fflush()` does, I think.

### C++ 2011

This table is based on the table of contents of ISO/IEC JTC1 SC22 WG21 Doc No: N3290 Date: 2011-04-11 Final Draft International Standard, Standard for Programming Language C++

In this implementation the `-std=gnu++11` or `-std=c++11` flag must be used to enable language and library features. See dialect options. The pre-defined symbol `__cplusplus` is used to check for the presence of the required flag. GCC 5.1 was the first release with non-experimental C++11 support, so the API and ABI of features added in C++11 is only stable since that release.

This status table is based on the table of contents of ISO/IEC 14882:2011.

This section describes the C++11 support in mainline GCC, not in any particular release.

Table 1.2. C++ 2011 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
18 | Language support
18.1 | General |  |
18.2 | Types | Y |
18.3 | Implementation properties |  |
18.3.2 | Numeric Limits |  |
18.3.2.3 | Class template `numeric_limits` | Y |
18.3.2.4 | `numeric_limits` members | Y |
18.3.2.5 | `float_round_style` | N |
18.3.2.6 | `float_denorm_style` | N |
18.3.2.7 | `numeric_limits` specializations | Y |
18.3.3 | C Library | Y |
18.4 | Integer types |  |
18.4.1 | Header `<cstdint>` synopsis | Y |
18.5 | Start and termination | Partial | C library dependency for quick_exit, at_quick_exit
18.6 | Dynamic memory management | Y |
18.7 | Type identification |  |
18.7.1 | Class type_info | Y |
18.7.2 | Class bad_cast | Y |
18.7.3 | Class bad_typeid | Y |
18.8 | Exception handling |  |
18.8.1 | Class exception | Y |
18.8.2 | Class bad_exception | Y |
18.8.3 | Abnormal termination | Y |
18.8.4 | `uncaught_exception` | Y |
18.8.5 | Exception Propagation | Y |
18.8.6 | `nested_exception` | Y |
18.9 | Initializer lists |  |
18.9.1 | Initializer list constructors | Y |
18.9.2 | Initializer list access | Y |
18.9.3 | Initializer list range access | Y |
18.10 | Other runtime support | Y |
19 | Diagnostics
19.1 | General |  |
19.2 | Exception classes | Y |
19.3 | Assertions | Y |
19.4 | Error numbers | Y |
19.5 | System error support |  |
19.5.1 | Class `error_category` | Y |
19.5.2 | Class `error_code` | Y |
19.5.3 | Class `error_condition` | Y |
19.5.4 | Comparison operators | Y |
19.5.5 | Class `system_error` | Y |
20 | General utilities
20.1 | General |  |
20.2 | Utility components |  |
20.2.1 | Operators | Y |
20.2.2 | swap | Y |
20.2.3 | forward/move helpers | Y |
20.2.4 | Function template `declval` | Y |
20.3 | Pairs |  |
20.3.1 | In general |  |
20.3.2 | Class template `pair` | Y |
20.3.3 | Specialized algorithms | Y |
20.3.4 | Tuple-like access to `pair` | Y |
20.3.5 | Piecewise construction | Y |
20.4 | Tuples |  |
20.4.1 | In general |  |
20.4.2 | Class template `tuple` |  |
20.4.2.1 | Construction | Y |
20.4.2.2 | Assignment | Y |
20.4.2.3 | Swap | Y |
20.4.2.4 | Tuple creation functions | Y |
20.4.2.5 | Tuple helper classes | Y |
20.4.2.6 | Element access | Y |
20.4.2.7 | Relational operators | Y |
20.4.2.8 | Tuple traits | Y |
20.4.2.9 | Tuple specialized algorithms | Y |
20.5 | Class template `bitset` | Y |
20.5.1 | `bitset` constructors | Y |
20.5.2 | `bitset` members | Y |
20.5.3 | `bitset` hash support | Y |
20.5.4 | `bitset` operators | Y |
20.6 | Memory |  |
20.6.1 | In general |  |
20.6.2 | Header `<memory>` synopsis |  |
20.6.3 | Pointer traits | Y |
20.6.4 | Pointer safety | Y |
20.6.5 | Align | Y |
20.6.6 | Allocator argument tag | Y |
20.6.7 | `uses_allocator` | Y |
20.6.8 | Allocator traits | Y |
20.6.9 | The default allocator | Y |
20.6.10 | Raw storage iterator | Y |
20.6.11 | Temporary buffers | Y |
20.6.12 | Specialized algorithms |  |
20.6.12.1 | `addressof` | Y |
20.6.12.2 | `uninitialized_copy` | Y |
20.6.12.3 | `uninitialized_fill` | Y |
20.6.12.4 | `uninitialized_fill_n` | Y |
20.6.13 | C library | Y |
20.7 | Smart pointers |  |
20.7.1 | Class template `unique_ptr` | Y |
20.7.2 | Shared-ownership pointers |  |
20.7.2.1 | Class `bad_weak_ptr` | Y |
20.7.2.2 | Class template `shared_ptr` | Y | Uses code from boost::shared_ptr.
20.7.2.3 | Class template `weak_ptr` | Y |
20.7.2.4 | Class template `enable_shared_from_this` | Y |
20.7.2.5 | `shared_ptr` atomic access | Y |
20.7.2.6 | Smart pointer hash support | Y |
20.8 | Function objects |  |
20.8.1 | Definitions |  |
20.8.2 | Requirements |  |
20.8.3 | Class template `reference_wrapper` | Y |
20.8.4 | Arithmetic operation | Y |
20.8.5 | Comparisons | Y |
20.8.6 | Logical operations | Y |
20.8.7 | Bitwise operations | Y |
20.8.8 | Negators | Y |
20.8.9 | Function template `bind` | Y |
20.8.10 | Function template `mem_fn` | Y |
20.8.11 | Polymorphic function wrappers |  |
20.8.11.1 | Class `bad_function_call` | Y |
20.8.11.2 | Class template `function` | Partial | Missing allocator support
20.8.12 | Class template `hash` | Y |
20.9 | Metaprogramming and type traits |  |
20.9.1 | Requirements | Y |
20.9.2 | Header `<type_traits>` synopsis |  |
20.9.3 | Helper classes | Y |
20.9.4 | Unary Type Traits | Y |
20.9.4.1 | Primary type categories | Y |
20.9.4.2 | Composite type traits | Y |
20.9.4.3 | Type properties | Y |
20.9.5 | Type property queries | Y |
20.9.6 | Relationships between types | Y |
20.9.7 | Transformations between types |  |
20.9.7.1 | Const-volatile modifications | Y |
20.9.7.2 | Reference modifications | Y |
20.9.7.3 | Sign modifications | Y |
20.9.7.4 | Array modifications | Y |
20.9.7.5 | Pointer modifications | Y |
20.9.7.6 | Other transformations | Y |
20.10 | Compile-time rational arithmetic |  |
20.10.1 | In general |  |
20.10.2 | Header `<ratio>` synopsis |  |
20.10.3 | Class template `ratio` | Y |
20.10.4 | Arithmetic on `ratio`s | Y |
20.10.5 | Comparison of `ratio`s | Y |
20.10.6 | SI types for `ratio` | Y |
20.11 | Time utilities |  |
20.11.3 | Clock requirements | Y |
20.11.4 | Time-related traits |  |
20.11.4.1 | `treat_as_floating_point` | Y |
20.11.4.2 | `duration_values` | Y |
20.11.4.3 | Specializations of `common_type` | Y |
20.11.5 | Class template `duration` | Y |
20.11.6 | Class template `time_point` | Y |
20.11.7 | Clocks |  |
20.11.7.1 | Class `system_clock` | Y |
20.11.7.2 | Class `steady_clock` | Y |
20.11.7.3 | Class `high_resolution_clock` | Y |
20.11.8 | Date and time functions | Y |
20.12 | Scoped allocator adaptor | Y |
20.12.1 | Header `<scoped_allocator>` synopsis |  |
20.12.2 | Scoped allocator adaptor member types | Y |
20.12.3 | Scoped allocator adaptor constructors | Y |
20.12.4 | Scoped allocator adaptor members | Y |
20.12.5 | Scoped allocator operators | Y |
20.13 | Class `type_index` | Y |
21 | Strings
21.1 | General | Y |
21.2 | Character traits |  |
21.2.1 | Character traits requirements | Y |
21.2.2 | traits typedefs | Y |
21.2.3 | `char_traits` specializations |  |
21.2.3.1 | struct `char_traits<char>` | Y |
21.2.3.2 | struct `char_traits<char16_t>` | Y |
21.2.3.3 | struct `char_traits<char32_t>` | Y |
21.2.3.4 | struct `char_traits<wchar_t>` | Y |
21.3 | String classes | Y |
21.4 | Class template `basic_string` | Y |
21.5 | Numeric Conversions | Y |
21.6 | Hash support | Y |
21.7 | Null-terminated sequence utilities | Partial | C library dependency.
22 | Localization
22.1 | General | Y |
22.2 | Header `<locale>` synopsis | Y |
22.3 | Locales |  |
22.3.1 | Class `locale` | Y |
22.3.2 | `locale` globals | Y |
22.3.3 | Convenience interfaces |  |
22.3.3.1 | Character classification | Y |
22.3.3.2 | Conversions |  |
22.3.3.2.1 | Character conversions | Y |
22.3.3.2.2 | `string` conversions | Y |
22.3.3.2.3 | Buffer conversions | Y |
22.4 | Standard `locale` categories |  |
22.4.1 | The `ctype` category | Y |
22.4.2 | The numeric category |  |
22.4.2.1 | `num_get` | Y |
22.4.2.2 | `num_put` | Y |
22.4.3 | The numeric punctuation facet | Y |
22.4.4 | The collate category | Y |
22.4.5 | The time category |  |
22.4.5.1 | Class template `time_get` | Y |
22.4.5.2 | Class template `time_get_byname` | Y |
22.4.5.3 | Class template `time_put` | Y |
22.4.5.3 | Class template `time_put_byname` | Y |
22.4.6 | The monetary category |  |
22.4.6.1 | Class template `money_get` | Y |
22.4.6.2 | Class template `money_put` | Y |
22.4.6.3 | Class template `money_punct` | Y |
22.4.6.4 | Class template `money_punct_byname` | Y |
22.4.7 | The message retrieval category | Y |
22.4.8 | Program-defined facets | Y |
22.5 | Standard code conversion facets | Y |
22.6 | C Library Locales | Y |
23 | Containers
23.1 | General |  |
23.2 | Container requirements |  |
23.2.1 | General container requirements | Y |
23.2.2 | Container data races | Y |
23.2.3 | Sequence containers | Y |
23.2.4 | Associative containers | Y |
23.2.5 | Unordered associative containers | Y |
23.3 | Sequence containers |  |
23.3.2 | Class template `array` | Y |
23.3.3 | Class template `deque` | Y |
23.3.4 | Class template `forward_list` | Y |
23.3.5 | Class template `list` | Y |
23.3.6 | Class template `vector` | Y |
23.3.7 | Class `vector<bool>` | Y |
23.4 | Associative containers |  |
23.4.4 | Class template `map` | Y |
23.4.5 | Class template `multimap` | Y |
23.4.6 | Class template `set` | Y |
23.4.7 | Class template `multiset` | Y |
23.5 | Unordered associative containers |  |
23.5.4 | Class template `unordered_map` | Y |
23.5.5 | Class template `unordered_multimap` | Y |
23.5.6 | Class template `unordered_set` | Y |
23.5.7 | Class template `unordered_multiset` | Y |
23.6 | Container adaptors |  |
23.6.1 | Class template `queue` | Y |
23.6.2 | Class template `priority_queue` | Y |
23.6.3 | Class template `stack` | Y |
24 | Iterators
24.1 | General | Y |
24.2 | Iterator requirements | Y |
24.3 | Header `<iterator>` synopsis | Y |
24.4 | Iterator primitives | Y |
24.5 | Iterator adaptors |  |
24.5.1 | Reverse iterators | Y |
24.5.2 | Insert iterators | Y |
24.5.3 | Move iterators | Y |
24.6 | Stream iterators |  |
24.6.1 | Class template `istream_iterator` | Y |
24.6.2 | Class template `ostream_iterator` | Y |
24.6.3 | Class template `istreambuf_iterator` | Y |
24.6.4 | Class template `ostreambuf_iterator` | Y |
24.6.5 | range access | Y |
25 | Algorithms
25.1 | General |  |
25.2 | Non-modifying sequence operations | Y |
25.3 | Mutating sequence operations | Y |
25.4 | Sorting and related operations | Y |
25.5 | C library algorithms | Y |
26 | Numerics
26.1 | General |  |
26.2 | Numeric type requirements | Y |
26.3 | The floating-point environment | Y |
26.4 | Complex numbers | Y |
26.5 | Random number generation |  |
26.5.1 | Requirements |  |
26.5.2 | Header `<random>` synopsis |  |
26.5.3 | Random number engine class templates |  |
26.5.3.1 | Class template `linear_congruential_engine` | Y |
26.5.3.2 | Class template `mersenne_twister_engine` | Y |
26.5.3.3 | Class template `subtract_with_carry_engine` | Y |
26.5.4 | Random number engine adaptor class templates |  |
26.5.4.2 | Class template `discard_block_engine` | Y |
26.5.4.3 | Class template `independent_bits_engine` | Y |
26.5.4.4 | Class template `shuffle_order_engine` | Y |
26.5.5 | Engines and engine adaptors with predefined parameters | Y |
26.5.6 | Class `random_device` | Y |
26.5.7 | Utilities |  |
26.5.7.1 | Class `seed_seq` | Y |
26.5.7.2 | Function template `generate_canonical` | Y |
26.5.8 | Random number distribution class templates |  |
26.5.8.2 | Uniform distributions |  |
26.5.8.2.1 | Class template `uniform_int_distribution` | Y |
26.5.8.2.2 | Class template `uniform_real_distribution` | Y |
26.5.8.3 | Bernoulli distributions |  |
26.5.8.3.1 | Class `bernoulli_distribution` | Y |
26.5.8.3.2 | Class template `binomial_distribution` | Y |
26.5.8.3.3 | Class template `geometric_distribution` | Y |
26.5.8.3.4 | Class template `negative_binomial_distribution` | Y |
26.5.8.4 | Poisson distributions |  |
26.5.8.4.1 | Class template `poisson_distribution` | Y |
26.5.8.4.2 | Class template `exponential_distribution` | Y |
26.5.8.4.3 | Class template `gamma_distribution` | Y |
26.5.8.4.4 | Class template `weibull_distribution` | Y |
26.5.8.4.5 | Class template `extreme_value_distribution` | Y |
26.5.8.5 | Normal distributions |  |
26.5.8.5.1 | Class template `normal_distribution` | Y |
26.5.8.5.2 | Class template `lognormal_distribution` | Y |
26.5.8.5.3 | Class template `chi_squared_distribution` | Y |
26.5.8.5.4 | Class template `cauchy_distribution` | Y |
26.5.8.5.5 | Class template `fisher_f_distribution` | Y |
26.5.8.5.6 | Class template `student_t_distribution` | Y |
26.5.8.6 | Sampling distributions |  |
26.5.8.6.1 | Class template `discrete_distribution` | Y |
26.5.8.6.2 | Class template `piecewise_constant_distribution` | Y |
26.5.8.6.3 | Class template `piecewise_linear_distribution` | Y |
26.6 | Numeric arrays |  |
26.6.1 | Header `<valarray>` synopsis | Y |
26.6.2 | Class template `valarray` | Y |
26.6.3 | `valarray` non-member operations | Y |
26.6.4 | Class `slice` | Y |
26.6.5 | Class template `slice_array` | Y |
26.6.6 | The `gslice` class | Y |
26.6.7 | Class template `gslice_array` | Y |
26.6.8 | Class template `mask_array` | Y |
26.6.9 | Class template `indirect_array` | Y |
26.6.10 | `valarray` range access | Y |
26.7 | Generalized numeric operations |  |
26.7.1 | Header `<numeric>` synopsis | Y |
26.7.2 | Accumulate> | Y |
26.7.3 | Inner product | Y |
26.7.4 | Partial sum | Y |
26.7.5 | Adjacent difference | Y |
26.7.6 | Iota | Y |
26.8 | C Library | Y |
27 | Input/output library
27.1 | General | Y |
27.2 | Iostreams requirements | Y |
27.2.1 | Imbue Limitations | Y |
27.2.2 | Positioning Type Limitations | Y |
27.2.3 | Thread safety | Partial |
27.3 | Forward declarations | Y |
27.4 | Standard iostream objects | Y |
27.4.1 | Overview | Y |
27.4.2 | Narrow stream objects | Y |
27.4.3 | Wide stream objects | Y |
27.5 | Iostreams base classes | Y |
27.6 | Stream buffers | Y |
27.7 | Formatting and manipulators | Y |
27.8 | String-based streams | Y |
27.9 | File-based streams | Y |
28 | Regular expressions
28.1 | General | Y |
28.2 | Definitions | Y |
28.3 | Requirements | Y |
28.4 | Header `<regex>` synopsis | Y |
28.5 | Namespace `std::regex_constants` | Y |
28.6 | Class `regex_error` | Y |
28.7 | Class template `regex_traits` | Partial | `transform_primary` is not correctly implemented
28.8 | Class template `basic_regex` | Y |
28.9 | Class template `sub_match` | Y |
28.10 | Class template `match_results` | Y |
28.11 | Regular expression algorithms | Y |
28.12 | Regular expression Iterators | Y |
28.13 | Modified ECMAScript regular expression grammar | Y |
29 | Atomic operations
29.1 | General | Y |
29.2 | Header `<atomic>` synopsis | Y |
29.3 | Order and consistency | Y |
29.4 | Lock-free property | Y |
29.5 | Atomic types | Y |
29.6 | Operations on atomic types | Y |
29.7 | Flag Type and operations | Y |
29.8 | Fences | Y |
30 | Thread support
30.1 | General | Y |
30.2 | Requirements | Y |
30.3 | Threads |  |
30.3.1 | Class `thread` | Partial | `thread::id` comparisons not well-defined
30.3.2 | Namespace `this_thread` | Y |
30.4 | Mutual exclusion |  |
30.4.1 | Mutex requirements |  |
30.4.1.1 | In general |  |
30.4.1.2 | Mutex types |  |
30.4.1.2.1 | Class `mutex` | Y |
30.4.1.2.2 | Class `recursive_mutex` | Y |
30.4.1.3 | Timed mutex types |  |
30.4.1.3.1 | Class `timed_mutex` | Y |
30.4.1.3.2 | Class `recursive_timed_mutex` | Y |
30.4.2 | Locks |  |
30.4.2.1 | Class template `lock_guard` | Y |
30.4.2.2 | Class template `unique_lock` | Y |
30.4.3 | Generic locking algorithms | Y |
30.4.4 | Call once |  |
30.4.4.1 | Struct `once_flag` | Y |
30.4.4.2 | Function `call_once` | Y | Exception support is broken. See PR 66146.
30.5 | Condition variables | Y |
30.5.1 | Class `condition_variable` | Y |
30.5.2 | Class `condition_variable_any` | Y |
30.6 | Futures |  |
30.6.1 | Overview |  |
30.6.2 | Error handling | Y |
30.6.3 | Class `future_error` | Y |
30.6.4 | Shared state | Y |
30.6.5 | Class template `promise` | Y |
30.6.6 | Class template `future` | Y |
30.6.7 | Class template `shared_future` | Y |
30.6.8 | Function template `async` | Y |
30.6.9 | Class template `packaged_task` | Y |
Appendix D | Compatibility features
D.1 | Increment operator with `bool` operand |  |
D.2 | `register` keyword |  |
D.3 | Implicit declaration of copy functions |  |
D.4 | Dynamic exception specifications |  |
D.5 | C standard library headers | Y |
D.6 | Old iostreams members | Y |
D.7 | `char*` streams | Y |
D.8 | Function objects | Y |
D.9 | Binders | Y |
D.10 | `auto_ptr` | Y |
D.11 | Violating exception-specifications | Y |

#### Implementation Specific Behavior

For behaviour which is also specified by the 1998 and 2003 standards, see C++ 1998/2003 Implementation Specific Behavior. This section only documents behaviour which is new in the 2011 standard.

17.6.5.12 [res.on.exception.handling] There are no implementation-defined exception classes, only standard exception classes (or classes derived from them) will be thrown.

17.6.5.14 [value.error.codes] The `error_category` for errors originating outside the OS, and the possible error code values for each error category, should be documented here.

18.6.2.2 [new.badlength] `what()` returns `"std::bad_array_new_length"`.

20.6.9.1 [allocator.member]/5 Over-aligned types are not supported by `std::allocator`.

20.7.2.2.1 [util.smartptr.shared.const] When a `shared_ptr` constructor fails `bad_alloc` (or types derived from it) will be thrown, or when an allocator is passed to the constructor then any exceptions thrown by the allocator.

20.7.2.0 [util.smartptr.weakptr] `what()` returns `"bad_weak_ptr"`.

20.8.11.1 [func.wrap.badcall] `what()` returns `"bad_function_call"`.

20.8.9.1.3 [func.bind.place]/1 There are 29 placeholders defined and the placeholder types are `CopyAssignable`.

20.11.7.1 [time.clock.system]/3, /4 Time point values are truncated to `time_t` values. There is no loss of precision for conversions in the other direction.

20.15.7 [meta.trans]/2 `aligned_storage` does not support extended alignment.

21.2.3.2 [char.traits.specializations.char16_t], 21.2.3.3 [char.traits.specializations.char32_t] The types `u16streampos` and `u32streampos` are both synonyms for `fpos<mbstate_t>`. The function `eof` returns `int_type(-1)`. `char_traits<char16_t>::to_int_type` will transform the "noncharacter" U+FFFF to U+FFFD (REPLACEMENT CHARACTER). This is done to ensure that `to_int_type` never returns the same value as `eof`, which is U+FFFF.

22.3.1 [locale] There is one global locale for the whole program, not per-thread.

22.4.5.1.2 [locale.time.get.virtuals], 22.4.5.3.2 [locale.time.put.virtuals] Additional supported formats should be documented here.

22.4.7.1.2 [locale.messages.virtuals] The mapping should be documented here.

23.3.2.1 [array.overview] `array<T, N>::iterator` is `T*` and `array<T, N>::const_iterator` is `const T*`.

23.5.4.2 [unord.map.cnstr], 23.5.5.2 [unord.multimap.cnstr], 23.5.6.2 [unord.set.cnstr], 23.5.7.2 [unord.multiset.cnstr] The default minimal bucket count is 0 for the default constructors, range constructors and initializer-list constructors.

25.3.12 [alg.random.shuffle] The two-argument overload of `random_shuffle` uses `rand` as the source of randomness.

26.5.5 [rand.predef] The type `default_random_engine` is a synonym for `minstd_rand0`.

26.5.6 [rand.device] The `token` parameter of the `random_device` constructor can be used to select a specific source of random bytes. The valid token values are shown in the list below. The default constructor uses the token `"default"`.

`"default"`
  Select the first available source from the other entries below. This is the only token that is always valid.
`"rand_s"`
  Use the MSVCRT `rand_s` function. This token is only valid for mingw-w64 targets.
`"rdseed"`, `"rdrand"` or `"rdrnd"`
  Use the IA-32 `RDSEED` or `RDRAND` instruction to read from an on-chip hardware random number generator. These tokens are only valid for x86 and x86_64 targets when both the assembler and CPU support the corresponding instruction.
`"darn"`
  Use the Power ISA-3.0 `DARN` ("Deliver A Random Number") instruction to read from an on-chip hardware random number generator. This token is only valid for 64-bit powerpc targets when both the assembler and CPU support the corresponding instruction.
`"hw"`, `"hardware"`
  Use any available CPU instruction to read from an on-chip hardware random number generator. This is equivalent to trying each of the following and using the first that is supported: `"rdseed"``"rdrand"``"darn"`
`"arc4random"`, `"getentropy"`
  Use the named C library function, if available on the target.
`"/dev/urandom"`, `"/dev/random"`
  Use the named character special file to read random bytes from. These tokens are only valid when the device files are present and readable by the current user.
`"mt19937"`, seed value
  When no source of nondeterministic random numbers is available a `mersenne_twister_engine` will be used. An integer seed value can be used as the token and will be converted to an `unsigned long` using `strtoul`. These tokens are only valid when no other source of random bytes is available.

An exception of type `runtime_error` will be thrown if a `random_device` object is constructed with an invalid token, or if it cannot open or read from the source of random bytes.

26.5.8.1 [rand.dist.general] The algorithms used by the distributions should be documented here.

26.8 [c.math] Whether the `rand` function introduces data races depends on the C library as the function is not provided by libstdc++.

27.8.2.1 [stringbuf.cons] Whether the sequence pointers are copied by the `basic_stringbuf` move constructor should be documented here.

27.9.1.2 [filebuf.cons] Whether the sequence pointers are copied by the `basic_filebuf` move constructor should be documented here.

28.5.1 [re.synopt], 28.5.2 [re.matchflag] , 28.5.3 [re.err] `syntax_option_type`, `match_flag_type` and `error_type` are unscoped enumeration types.

28.7 [re.traits] The `blank` character class corresponds to the `ctype_base::blank` mask.

29.4 [atomics.lockfree] The values of the `ATOMIC_xxx_LOCK_FREE` macros depend on the target and cannot be listed here.

30.2.3 [thread.req.native]/1 `native_handle_type` and `native_handle` are provided. The handle types are defined in terms of the Gthreads abstraction layer, although this is subject to change at any time. Any use of `native_handle` is inherently non-portable and not guaranteed to work between major releases of GCC.

`thread`
  The native handle type is a typedef for `__gthread_t` i.e. `pthread_t` when GCC is configured with the `posix` thread model. The value of the native handle is undefined for a thread which is not joinable.
`mutex`, `timed_mutex`
  The native handle type is `__gthread_mutex_t*` i.e. `pthread_mutex_t*` for the `posix` thread model.
`recursive_mutex`, `recursive_timed_mutex`
  The native handle type is `__gthread_recursive_mutex_t*` i.e. `pthread_mutex_t*` for the `posix` thread model.
`condition_variable`
  The native handle type is `__gthread_cond_t*` i.e. `pthread_cond_t*` for the `posix` thread model.

30.6.1 [futures.overview]/2 `launch` is a scoped enumeration type with overloaded operators to support bitmask operations. There are no additional bitmask elements defined.

### C++ 2014

In this implementation the `-std=gnu++14` or `-std=c++14` flag must be used to enable language and library features. See dialect options. The pre-defined symbol `__cplusplus` is used to check for the presence of the required flag. GCC 6.1 was the first release with non-experimental C++14 support, so the API and ABI of features added in C++14 is only stable since that release.

This status table is based on the table of contents of ISO/IEC 14882:2014. Some subclauses are not shown in the table where the content is unchanged since C++11 and the implementation is complete.

This section describes the C++14 and library TS support in mainline GCC, not in any particular release.

Table 1.3. C++ 2014 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
18 | Language support
18.1 | General |  |
18.2 | Types | Y |
18.3 | Implementation properties |  |
18.3.2 | Numeric Limits |  |
18.3.2.3 | Class template `numeric_limits` | Y |
18.3.2.4 | `numeric_limits` members | Y |
18.3.2.5 | `float_round_style` | N |
18.3.2.6 | `float_denorm_style` | N |
18.3.2.7 | `numeric_limits` specializations | Y |
18.3.3 | C Library | Y |
18.4 | Integer types |  |
18.4.1 | Header `<cstdint>` synopsis | Y |
18.5 | Start and termination | Partial | C library dependency for quick_exit, at_quick_exit
18.6 | Dynamic memory management | Y |
18.7 | Type identification |  |
18.7.1 | Class type_info | Y |
18.7.2 | Class bad_cast | Y |
18.7.3 | Class bad_typeid | Y |
18.8 | Exception handling |  |
18.8.1 | Class exception | Y |
18.8.2 | Class bad_exception | Y |
18.8.3 | Abnormal termination | Y |
18.8.4 | `uncaught_exception` | Y |
18.8.5 | Exception Propagation | Y |
18.8.6 | `nested_exception` | Y |
18.9 | Initializer lists |  |
18.9.1 | Initializer list constructors | Y |
18.9.2 | Initializer list access | Y |
18.9.3 | Initializer list range access | Y |
18.10 | Other runtime support | Y |
19 | Diagnostics
19.1 | General |  |
19.2 | Exception classes | Y |
19.3 | Assertions | Y |
19.4 | Error numbers | Y |
19.5 | System error support |  |
19.5.1 | Class `error_category` | Y |
19.5.2 | Class `error_code` | Y |
19.5.3 | Class `error_condition` | Y |
19.5.4 | Comparison operators | Y |
19.5.5 | Class `system_error` | Y |
20 | General utilities
20.1 | General |  |
20.2 | Utility components |  |
20.2.1 | Operators | Y |
20.2.2 | swap | Y |
20.2.3 | exchange | Y |
20.2.4 | forward/move helpers | Y |
20.2.5 | Function template `declval` | Y |
20.3 | Pairs | Y |
20.4 | Tuples | Y |
20.5 | Compile-time integer sequences |  |
20.5.2 | Class template `integer_sequence` | Y |
20.5.3 | Alias template `make_integer_sequence` | Y |
20.6 | Class template `bitset` | Y |
20.7 | Memory | Y |
20.8 | Smart pointers |  |
20.8.1 | Class template `unique_ptr` | Y |
20.8.1.1 | Default deleters | Y |
20.8.1.2 | `unique_ptr` for single objects | Y |
20.8.1.3 | `unique_ptr` for array objects with a runtime length | Y |
20.8.1.4 | `unique_ptr` creation | Y |
20.8.1.5 | `unique_ptr` specialized algorithms | Y |
20.8.2 | Shared-ownership pointers |  |
20.8.2.1 | Class `bad_weak_ptr` | Y |
20.8.2.2 | Class template `shared_ptr` | Y | Uses code from boost::shared_ptr.
20.8.2.3 | Class template `weak_ptr` | Y |
20.8.2.4 | Class template `owner_less` | Y |
20.8.2.5 | Class template `enable_shared_from_this` | Y |
20.8.2.6 | `shared_ptr` atomic access | Y |
20.8.2.7 | Smart pointer hash support | Y |
20.9 | Function objects |  |
20.9.1 | Definitions |  |
20.9.2 | Requirements |  |
20.9.3 | Class template `reference_wrapper` | Y |
20.9.4 | Arithmetic operation | Y |
20.9.5 | Comparisons | Y |
20.8.6 | Logical operations | Y |
20.9.7 | Bitwise operations | Y |
20.9.8 | Negators | Y |
20.9.9 | Function object binders | Y |
20.9.10 | Function template `mem_fn` | Y |
20.9.11 | Polymorphic function wrappers |  |
20.9.11.1 | Class `bad_function_call` | Y |
20.9.11.2 | Class template `function` | Partial | Missing allocator support
20.9.12 | Class template `hash` | Y |
20.10 | Metaprogramming and type traits |  |
20.10.1 | Requirements | Y |
20.10.2 | Header `<type_traits>` synopsis |  |
20.10.3 | Helper classes | Y |
20.10.4 | Unary Type Traits | Y |
20.10.5 | Type property queries | Y |
20.10.6 | Relationships between types | Y |
20.10.7 | Transformations between types | Y |
20.11 | Compile-time rational arithmetic | Y |
20.12 | Time utilities |  |
20.12.3 | Clock requirements | Y |
20.12.4 | Time-related traits | Y |
20.12.5 | Class template `duration` | Y |
20.12.5.8 | Suffixes for duration literals | Y |
20.12.6 | Class template `time_point` | Y |
20.12.7 | Clocks | Y |
20.12.8 | Date and time functions | Y |
20.13 | Scoped allocator adaptor | Y |
20.14 | Class `type_index` | Y |
21 | Strings
21.1 | General | Y |
21.2 | Character traits | Y |
21.3 | String classes | Y |
21.4 | Class template `basic_string` | Y |
21.5 | Numeric Conversions | Y |
21.6 | Hash support | Y |
21.7 | Suffixes for `basic_string` literals | Y |
21.7 | Null-terminated sequence utilities | Partial | C library dependency.
22 | Localization
22.1 | General | Y |
22.2 | Header `<locale>` synopsis | Y |
22.3 | Locales | Y |
22.4 | Standard `locale` categories | Y |
22.5 | Standard code conversion facets | Y |
22.6 | C Library Locales | Y |
23 | Containers
23.1 | General |  |
23.2 | Container requirements | Y |
23.3 | Sequence containers | Y |
23.4 | Associative containers | Y |
23.5 | Unordered associative containers | Y |
23.6 | Container adaptors | Y |
24 | Iterators
24.1 | General | Y |
24.2 | Iterator requirements | Y |
24.3 | Header `<iterator>` synopsis | Y |
24.4 | Iterator primitives | Y |
24.5 | Iterator adaptors | Y |
24.6 | Stream iterators | Y |
24.7 | range access | Y |
25 | Algorithms
25.1 | General |  |
25.2 | Non-modifying sequence operations | Y |
25.3 | Mutating sequence operations | Y |
25.4 | Sorting and related operations | Y |
25.5 | C library algorithms | Y |
26 | Numerics
26.1 | General |  |
26.2 | Numeric type requirements | Y |
26.3 | The floating-point environment | Y |
26.4 | Complex numbers | Y |
26.4.10 | Suffixes for complex number literals | Y |
26.5 | Random number generation | Y |
26.6 | Numeric arrays | Y |
26.7 | Generalized numeric operations | Y |
26.8 | C Library | Y |
27 | Input/output library
27.1 | General | Y |
27.2 | Iostreams requirements | Y |
27.2.1 | Imbue Limitations | Y |
27.2.2 | Positioning Type Limitations | Y |
27.2.3 | Thread safety | Partial |
27.3 | Forward declarations | Y |
27.4 | Standard iostream objects | Y |
27.5 | Iostreams base classes | Y |
27.6 | Stream buffers | Y |
27.7 | Formatting and manipulators | Y |
27.7.6 | Quoted manipulators | Y |
27.8 | String-based streams | Y |
27.9 | File-based streams | Y |
28 | Regular expressions
28.1 | General | Y |
28.2 | Definitions | Y |
28.3 | Requirements | Y |
28.4 | Header `<regex>` synopsis | Y |
28.5 | Namespace `std::regex_constants` | Y |
28.6 | Class `regex_error` | Y |
28.7 | Class template `regex_traits` | Partial | `transform_primary` is not correctly implemented
28.8 | Class template `basic_regex` | Y |
28.9 | Class template `sub_match` | Y |
28.10 | Class template `match_results` | Y |
28.11 | Regular expression algorithms | Y |
28.12 | Regular expression Iterators | Y |
28.13 | Modified ECMAScript regular expression grammar | Y |
29 | Atomic operations
29.1 | General | Y |
29.2 | Header `<atomic>` synopsis | Y |
29.3 | Order and consistency | Y |
29.4 | Lock-free property | Y |
29.5 | Atomic types | Y |
29.6 | Operations on atomic types | Y |
29.7 | Flag Type and operations | Y |
29.8 | Fences | Y |
30 | Thread support
30.1 | General | Y |
30.2 | Requirements | Y |
30.3 | Threads |  |
30.3.1 | Class `thread` | Partial | `thread::id` comparisons not well-defined
30.3.2 | Namespace `this_thread` | Y |
30.4 | Mutual exclusion |  |
30.4.1 | Mutex requirements |  |
30.4.1.1 | In general |  |
30.4.1.2 | Mutex types |  |
30.4.1.2.1 | Class `mutex` | Y |
30.4.1.2.2 | Class `recursive_mutex` | Y |
30.4.1.3 | Timed mutex types |  |
30.4.1.3.1 | Class `timed_mutex` | Y |
30.4.1.3.2 | Class `recursive_timed_mutex` | Y |
30.4.1.4 | Shared timed mutex types |  |
30.4.1.4.1 | Class `shared_timed_mutex` | Y |
30.4.2 | Locks |  |
30.4.2.1 | Class template `lock_guard` | Y |
30.4.2.2 | Class template `unique_lock` | Y |
30.4.2.3 | Class template `shared_lock` | Y |
30.4.3 | Generic locking algorithms | Y |
30.4.4 | Call once |  |
30.4.4.1 | Struct `once_flag` | Y |
30.4.4.2 | Function `call_once` | Broken | Exception support is broken. See PR 66146.
30.5 | Condition variables | Y |
30.5.1 | Class `condition_variable` | Y |
30.5.2 | Class `condition_variable_any` | Y |
30.6 | Futures |  |
30.6.1 | Overview |  |
30.6.2 | Error handling | Y |
30.6.3 | Class `future_error` | Y |
30.6.4 | Shared state | Y |
30.6.5 | Class template `promise` | Y |
30.6.6 | Class template `future` | Y |
30.6.7 | Class template `shared_future` | Y |
30.6.8 | Function template `async` | Y |
30.6.9 | Class template `packaged_task` | Y |
Appendix D | Compatibility features
D.1 | Increment operator with `bool` operand |  |
D.2 | `register` keyword |  |
D.3 | Implicit declaration of copy functions |  |
D.4 | Dynamic exception specifications |  |
D.5 | C standard library headers | Y |
D.6 | Old iostreams members | Y |
D.7 | `char*` streams | Y |
D.8 | Function objects | Y |
D.9 | Binders | Y |
D.10 | `auto_ptr` | Y |
D.11 | Violating exception-specifications | Y |
D.12 | Random shuffle | Y |

Table 1.4. C++ Technical Specifications Implementation Status

Paper | Title | Status | Comments
--- | --- | --- | ---
N3662 | C++ Dynamic Arrays | N | Array Extensions TS
N3793 | A proposal to add a utility class to represent optional objects | Y | Library Fundamentals TS
N3804 | Any library proposal | Y | Library Fundamentals TS
N3866 | Invocation type traits, but dropping function_call_operator. | N | Library Fundamentals TS
N3905 | Faster string searching (Boyer-Moore et al.) | Y | Library Fundamentals TS
N3915 | apply() call a function with arguments from a tuple | Y | Library Fundamentals TS
N3916 | Polymorphic memory resources | Partial (missing pool resource and buffer resource classes) | Library Fundamentals TS
N3920 | Extending shared_ptr to support arrays | Y | Library Fundamentals TS
N3921 | `string_view`: a non-owning reference to a string | Y | Library Fundamentals TS
N3925 | A sample proposal | Y | Library Fundamentals TS
N3932 | Variable Templates For Type Traits | Y | Library Fundamentals TS
N4100 | File System | Y | Link with `-lstdc++fs`

#### Implementation Specific Behavior

##### Filesystem TS

2.1 POSIX conformance [fs.conform.9945] The behavior of the filesystem library implementation will depend on the target operating system. Some features will not be supported on some targets. Symbolic links and file permissions are not supported on Windows.

15.30 Rename [fs.op.rename] On Windows, `experimental::filesystem::rename` is implemented by calling `MoveFileExW` and so does not meet the requirements of POSIX `rename` when one or both of the paths resolves to an existing directory. Specifically, it is possible to rename a directory so it replaces a non-directory (POSIX requires an error in that case), and it is not possible to rename a directory to replace another directory (POSIX requires that to work if the directory being replaced is empty).

### C++ 2017

In this implementation the `-std=gnu++17` or `-std=c++17` flag must be used to enable language and library features. See dialect options. The pre-defined symbol `__cplusplus` is used to check for the presence of the required flag. GCC 9.1 was the first release with non-experimental C++17 support, so the API and ABI of features added in C++17 is only stable since that release.

This section describes the C++17 and library TS support in mainline GCC, not in any particular release.

The following table lists new library features that are included in the C++17 standard. The "Proposal" column provides a link to the ISO C++ committee proposal that describes the feature, while the "Status" column indicates the first version of GCC that contains an implementation of this feature (if it has been implemented). The "SD-6 Feature Test" column shows the corresponding macro or header from SD-6: Feature-testing recommendations for C++.

Table 1.5. C++ 2017 Library Features

Library Feature | Proposal | Status | SD-6 Feature Test
--- | --- | --- | ---
`constexpr std::hardware_{constructive,destructive}_interference_size` | P0154R1 | 12.1 | `__cpp_lib_hardware_interference_size >= 201603`
Core Issue 1776: Replacement of class objects containing reference members | P0137R1 | 7.1 | `__cpp_lib_launder >= 201606`
Wording for `std::uncaught_exceptions` | N4259 | 6.1 | `__cpp_lib_uncaught_exceptions >= 201411`
C++17 should refer to C11 instead of C99 | P0063R3 | 9.1 |
Variant: a type-safe union for C++17 | P0088R3 | 7.1 | `__has_include(<variant>)`, `__cpp_lib_variant >= 201603` (since 7.3, see Note 1)
Library Fundamentals V1 TS Components: `optional` | P0220R1 | 7.1 | `__has_include(<optional>)`, `__cpp_lib_optional >= 201603` (since 7.3, see Note 1)
Library Fundamentals V1 TS Components: `any` | P0220R1 | 7.1 | `__has_include(<any>)`, `__cpp_lib_any >= 201603` (since 7.3, see Note 1)
Library Fundamentals V1 TS Components: `string_view` | P0220R1 | 7.1 | `__has_include(<string_view>)`, `__cpp_lib_string_view >= 201603` (since 7.3, see Note 1)
Library Fundamentals V1 TS Components: `memory_resource` | P0220R1 | 9.1 | `__has_include(<memory_resource>)`, `__cpp_lib_memory_resource >= 201603`
Library Fundamentals V1 TS Components: `apply` | P0220R1 | 7.1 | `__cpp_lib_apply >= 201603`
Library Fundamentals V1 TS Components: `shared_ptr<T[]>` | P0220R1 | 7.1 | `__cpp_lib_shared_ptr_arrays >= 201603`
Library Fundamentals V1 TS Components: Searchers | P0220R1 | 7.1 | `__cpp_lib_boyer_moore_searcher >= 201603`
Library Fundamentals V1 TS Components: Sampling | P0220R1 | 7.1 | `__cpp_lib_sample >= 201603`
Constant View: A proposal for a `std::as_const` helper function template | P0007R1 | 7.1 | `__cpp_lib_as_const >= 201510`
Improving pair and tuple | N4387 | 6.1 | N/A
`make_from_tuple`: apply for construction | P0209R2 | 7.1 | `__cpp_lib_make_from_tuple >= 201606`
Removing `auto_ptr`, `random_shuffle()`, And Old `<functional>` Stuff | N4190 | No (kept for backwards compatibility) |
Deprecating Vestigial Library Parts in C++17 | P0174R2 | 12.1 |
Making `std::owner_less` more flexible | P0074R0 | 7.1 | `__cpp_lib_transparent_operators >= 201510`
`std::addressof` should be constexpr | LWG2296 | 7.1 | `__cpp_lib_addressof_constexpr >= 201603`
Safe conversions in `unique_ptr<T[]>` | N4089 | 6 |
LWG 2228: Missing SFINAE rule in unique_ptr templated assignment | N4366 | 6 |
Re-enabling `shared_from_this` | P0033R1 | 7.1 | `__cpp_lib_enable_shared_from_this >= 201603`
A proposal to add `invoke` function template | N4169 | 6.1 | `__cpp_lib_invoke >= 201411`
TriviallyCopyable `reference_wrapper` | N4277 | 5.1 |
Adopt `not_fn` from Library Fundamentals 2 for C++17 | P0005R4 | 7.1 | `__cpp_lib_not_fn >= 201603`
Fixes for `not_fn` | P0358R1 | 7.1 |
Fixing a design mistake in the searchers interface in Library Fundamentals | P0253R1 | 7.1 |
Extending memory management tools | P0040R3 | 7.1 | `__cpp_lib_raw_memory_algorithms >= 201606L`
`shared_ptr::weak_type` | P0163R0 | 7.1 | `__cpp_lib_shared_ptr_weak_type >= 201606`
Transformation Trait Alias `void_t` | N3911 | 6.1 | `__cpp_lib_void_t >= 201411`
Wording for `bool_constant`, revision 1 | N4389 | 6.1 | `__cpp_lib_bool_constant >= 201505`
Adopt Type Traits Variable Templates from Library Fundamentals TS for C++17 | P0006R0 | 7.1 | `__cpp_lib_type_trait_variable_templates >= 201510`
Logical Operator Type Traits | P0013R1 | 6.1 | `__cpp_lib_logical_traits >= 201510`
Adding [nothrow-]swappable traits | P0185R1 | 7.1 (`__is_swappable` available since 6.1) | `__cpp_lib_is_swappable >= 201603`
`is_callable`, the missing INVOKE related trait | P0077R2 | 7.1 | `__cpp_lib_is_invocable >= 201703`
has_unique_object_representations | P0258R2 | 7.1 | `__cpp_lib_has_unique_object_representations >= 201606`
Polishing `<chrono>` | P0092R1 | 7.1 | `__cpp_lib_chrono >= 201510`
Adding more constexpr to `<chrono>` | P0505R0 | 7.1 | `__cpp_lib_chrono >= 201611` (since 7.3, see Note 2)
Constexpr for `std::char_traits` | P0426R1 | 8.1 | `__cpp_lib_constexpr_string >= 201611`
Integrating `std::string_view` and `std::string` | P0254R2 | 7.1 | ``
Give 'std::string' a non-const '.data()' member function | P0272R1 | 7.1 | ``
Cleaning-up noexcept in the Library | N4258 | 6.1 | `__cpp_lib_allocator_traits_is_always_equal >= 201411`
Contiguous Iterators | N4284 | N/A |
Minimal incomplete type support for standard containers | N4510 | 3.0 | `__cpp_lib_incomplete_container_elements >= 201505` (since 6.2, see Note 2)
Emplace return type | P0084R2 | 7.1 |
Improved insertion interface for unique-key maps | N4279 | 6.1 | `__cpp_lib_map_try_emplace >= 201411`, `__cpp_lib_unordered_map_try_emplace >= 201411`
Splicing Maps and Sets | P0083R3 | 7.1 | `__cpp_lib_node_extract >= 201606`
Non-member `size()` and more | N4280 | 6.1 | `__cpp_lib_nonmember_container_access >= 201411`
A Proposal to Add Constexpr Modifiers to `reverse_iterator`, `move_iterator`, `array` and Range Access | P0031R0 | 7.1 | `__cpp_lib_array_constexpr >= 201603`
The Parallelism TS Should be Standardized | P0024R2 | 9.1 | `__has_include(<execution>)`, `__cpp_lib_execution >= 201603` , `__cpp_lib_parallel_algorithm >= 201603` (requires linking with `-ltbb`, see Note 3)
An algorithm to "clamp" a value between a pair of boundary values | P0025R0 | 7.1 | `__cpp_lib_clamp >= 201603`
Adopt Selected Library Fundamentals V2 Components for C++17 | P0295R0 | 7.1 | `__cpp_lib_gcd_lcm >= 201606`
Proposal to Introduce a 3-Argument Overload to `std::hypot` | P0030R1 | 7.1 | `__cpp_lib_hypot >= 201603`
Mathematical Special Functions for C++17 | P0226R1 | 7.1 | `__cpp_lib_math_special_functions >= 201603` (see Note 4)
Adopt the File System TS for C++17 | P0218R1 | 8.1 | `__has_include(<filesystem>)`, `__cpp_lib_filesystem >= 201603` (GCC 8.x requires linking with `-lstdc++fs`)
Relative Paths for Filesystem | P0219R1 | 8.1 | `__cpp_lib_filesystem >= 201606`
Adapting string_view by filesystem paths | P0392R0 | 8.1 | `__cpp_lib_filesystem >= 201606`
Directory Entry Caching for Filesystem | P0317R1 | 8.1 | `__cpp_lib_filesystem >= 201703`
constexpr `atomic<T>::is_always_lock_free` | P0152R1 | 7.1 | `__cpp_lib_atomic_is_always_lock_free >= 201603`
A proposal to add `shared_mutex` (untimed) (Revision 4) | N4508 | 6.1 | `__cpp_lib_shared_mutex >= 201505`
Variadic `lock_guard` (Rev. 5) | P0156R2 | 7.1 | `__cpp_lib_scoped_lock >= 201703`
A byte type definition | P0298R3 | 7.1 | `__cpp_lib_byte >= 201603` (since 7.3, see Note 2)
Elementary string conversions | P0067R5 | 11.1 (integral types supported since 8.1) | `__has_include(<charconv>)`, `__cpp_lib_to_chars >= 201611`
Homogeneous interface for variant, any and optional | P0032R3 | 7.1 | `__cpp_lib_any >= 201606` , `__cpp_lib_optional >= 201606` , `__cpp_lib_variant >= 201606`
Making Optional Greater Equal Again | P0307R2 | 7.1 | `__cpp_lib_optional >= 201606`

Note 1: This feature is supported in GCC 7.1 and 7.2 but before GCC 7.3 the `__cpp_lib` macro is not defined, and compilation will fail if the header is included without using `-std` to enable C++17 support.

Note 2: This feature is supported in older releases but the `__cpp_lib` macro is not defined to the right value (or not defined at all) until the version shown in parentheses.

Note 3: The Parallel Algorithms have an external dependency on Intel TBB 2018 or later. If the `<execution>` header is included then `-ltbb` must be used to link to TBB.

Note 4: The mathematical special functions are enabled in C++17 mode from GCC 7.1 onwards. For GCC 6.x or for C++11/C++14 define `__STDCPP_WANT_MATH_SPEC_FUNCS__` to a non-zero value and test for `__STDCPP_MATH_SPEC_FUNCS__ >= 201003L`.

The following status table is based on the table of contents of ISO/IEC 14882:2017. Some subclauses are not shown in the table where the content is unchanged since C++14 and the implementation is complete.

Table 1.6. C++ 2017 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
21 | Language support
21.1 | General |  |
21.2 | Common definitions |  |
21.3 | Implementation properties |  |
21.3.1 | General |  |
21.3.2 | Header `<limits>` synopsis |  |
21.3.3 | Floating-point type properties |  |
21.3.3.1 | `float_round_style` | N |
21.3.3.2 | `float_denorm_style` | N |
21.3.4 | Class template `numeric_limits` | Y |
21.3.5 | Header `<climits>` synopsis | Y |
21.3.6 | Header `<cfloat>` synopsis | Y |
21.4 | Integer types |  |
21.4.1 | Header `<cstdint>` synopsis | Y |
21.5 | Start and termination | Partial | C library dependency for quick_exit, at_quick_exit
21.6 | Dynamic memory management |  |
21.6.1 | Header `<new>` synopsis |  |
21.6.2 | Storage allocation and deallocation | Y |
21.6.3 | Storage allocation errors | Y |
21.6.4 | Pointer optimization barrier | Y |
21.6.5 | Hardware interference size | Y |
21.7 | Type identification | Y |
21.8 | Exception handling |  |
21.8.1 | Header `<exception>` synopsis |  |
21.8.2 | Class exception | Y |
21.8.3 | Class bad_exception | Y |
21.8.4 | Abnormal termination | Y |
21.8.5 | `uncaught_exceptions` | Y |
21.8.6 | Exception Propagation | Y |
21.8.7 | `nested_exception` | Y |
21.9 | Initializer lists | Y |
21.10 | Other runtime support | Y |
22 | Diagnostics
22.1 | General |  |
22.2 | Exception classes | Y |
22.3 | Assertions | Y |
22.4 | Error numbers | Y |
22.5 | System error support |  |
23 | General utilities
23.1 | General |  |
23.2 | Utility components |  |
23.2.1 | Header `<utility>` synopsis |  |
23.2.2 | Operators | Y |
23.2.3 | `swap` | Y |
23.2.4 | `exchange` | Y |
23.2.5 | Forward/move helpers | Y |
23.2.6 | Function template `as_const` | Y |
23.2.7 | Function template `declval` | Y |
23.2.8 | Primitive numeric output conversion | Y | Floating-point types up to 64-bit are formatted using Ryu. Types with greater precision are formatted using the C library (`sprintf` and conditionally `strfromf128`). For powerpc64le-unknown-linux-gnu `__sprintfieee128` must be provided by Glibc.
23.2.9 | Primitive numeric input conversion | Y | Floating-point types up to 64-bit are parsed using fast_float. Types with greater precision are parsed using the C library (`strtold`). For powerpc64le-unknown-linux-gnu `__strtoieee128` must be provided by Glibc.
23.3 | Compile-time integer sequences |  |
23.4 | Pairs | Y |
23.5 | Tuples | Y |
23.6 | Optional objects | Y |
23.7 | Variants | Y |
23.8 | Storage for any type | Y |
23.9 | Bitsets | Y |
23.10 | Memory | Y |
23.10.1 | In general |  |
23.10.2 | Header `<memory>` synopsis | Y |
23.10.3 | Pointer traits | Y |
23.10.4 | Pointer safety | Y |
23.10.5 | Align | Y |
23.10.6 | Allocator argument tag | Y |
23.10.7 | `uses_allocator` | Y |
23.10.8 | Allocator traits | Y |
23.10.9 | The default allocator | Y |
23.10.10 | Specialized algorithms | Y |
23.10.11 | C library memory allocation | Y |
23.11 | Smart pointers |  |
23.11.1 | Class template `unique_ptr` | Y |
23.11.2 | Shared-ownership pointers | Y |
23.12 | Memory resources |  |
23.12.1 | Header `<memory_resource>` synopsis | Y |
23.12.2 | Class `memory_resource` | Y |
23.12.3 | Class template `polymorphic_allocator` | Y |
23.12.4 | Access to program-wide `memory_resource` objects | Y |
23.12.5 | Pool resource classes | Y |
23.12.6 | Class `monotonic_buffer_resource` | Y |
23.13 | Class template `scoped_allocator_adaptor` | Y |
23.14 | Function objects |  |
23.14.1 | Header `<functional>` synopsis |  |
23.14.2 | Definitions |  |
23.14.3 | Requirements |  |
23.14.4 | Function template `invoke` | Y |
23.14.5 | Class template `reference_wrapper` | Y |
23.14.6 | Arithmetic operation | Y |
23.14.7 | Comparisons | Y |
23.14.8 | Logical operations | Y |
23.14.9 | Bitwise operations | Y |
23.14.10 | Function template `not_fn` | Y |
23.14.11 | Function object binders | Y |
23.14.12 | Function template `mem_fn` | Y |
23.14.13 | Polymorphic function wrappers | Y |
23.14.14 | Searchers | Y |
23.14.15 | Class template `hash` | Y |
23.15 | Metaprogramming and type traits |  |
23.15.1 | Requirements |  |
23.15.2 | Header `<type_traits>` synopsis | Y |
23.15.3 | Helper classes | Y |
23.15.4 | Unary Type Traits | Y |
23.15.5 | Type property queries | Y |
23.15.6 | Relationships between types | Y |
23.15.7 | Transformations between types | Y |
23.15.8 | Logical operator traits | Y |
23.16 | Compile-time rational arithmetic | Y |
23.17.1 | In general |  |
23.17.2 | Header `<chrono>` synopsis |  |
23.17 | Time utilities |  |
23.17.3 | Clock requirements | Y |
23.17.4 | Time-related traits | Y |
23.17.5 | Class template `duration` | Y |
23.17.6 | Class template `time_point` | Y |
23.17.7 | Clocks | Y |
23.17.8 | Header `<ctime>` synopsis | Y |
23.18 | Class `type_index` | Y |
23.19 | Execution policies |  |
23.19.1 | In general |  |
23.19.2 | Header `<execution>` synopsis |  |
23.19.3 | Execution policy type trait | Y |
23.19.4 | Sequenced execution policy | Y |
23.19.5 | Parallel execution policy | Y |
23.19.6 | Parallel and unsequenced execution policy | Y |
23.19.7 | Execution policy objects | Y |
24 | Strings
24.1 | General |  |
24.2 | Character traits | Y |
24.3 | String classes | Y |
24.4 | String view classes | Y |
24.4.1 | Header `<string_view>` synopsis | Y |
24.4.2 | Class template `basic_string_view` | Y |
24.4.3 | Non-member comparison functions | Y |
24.4.4 | Inserters and extractors | Y |
24.4.5 | Hash support | Y |
24.4.6 | Suffix for `basic_string_view` literals | Y |
24.5 | Null-terminated sequence utilities | Partial | C library dependency.
25 | Localization
25.1 | General | Y |
25.2 | Header `<locale>` synopsis | Y |
25.3 | Locales | Y |
25.4 | Standard `locale` categories | Y |
25.5 | C Library Locales | Y |
26 | Containers
26.1 | General |  |
26.2 | Container requirements | Y |
26.3 | Sequence containers | Y |
26.4 | Associative containers | Y |
26.5 | Unordered associative containers | Y |
26.6 | Container adaptors | Y |
27 | Iterators
27.1 | General | Y |
27.2 | Iterator requirements | Y |
27.3 | Header `<iterator>` synopsis | Y |
27.4 | Iterator primitives | Y |
27.5 | Iterator adaptors | Y |
27.6 | Stream iterators | Y |
27.7 | Range access | Y |
27.8 | Container access | Y |
28 | Algorithms
28.1 | General |  |
28.2 | Header `<algorithm>` synopsis |  |
28.3 | Algorithms requirements |  |
28.4 | Parallel algorithms |  | Uses code from oneDPL
28.5 | Non-modifying sequence operations | Y |
28.6 | Mutating sequence operations | Y |
28.7 | Sorting and related operations | Y |
28.8 | C library algorithms | Y |
29 | Numerics
29.1 | General |  |
29.2 | Definitions |  |
29.3 | Numeric type requirements | Y |
29.4 | The floating-point environment | Y |
29.5 | Complex numbers | Y |
29.6 | Random number generation | Y |
29.7 | Numeric arrays | Y |
29.8 | Generalized numeric operations |  |
29.8.1 | Header `<numeric>` synopsis |  |
29.8.2 | Accumulate | Y |
29.8.3 | Reduce | Y |
29.8.4 | Inner product | Y |
29.8.5 | Transform reduce | Y |
29.8.6 | Partial sum | Y |
29.8.7 | Exclusive scan | Y |
29.8.8 | Inclusive scan | Y |
29.8.9 | Transform exclusive scan | Y |
29.8.10 | Transform inclusive scan | Y |
29.8.11 | Adjacent difference | Y |
29.8.12 | Iota | Y |
29.8.13 | Greatest common divisor | Y |
29.8.14 | Least common multiple | Y |
29.9 | Mathematical functions for floating-point types |  |
29.9.1 | Header `<cmath>` synopsis |  |
29.9.2 | Absolute values | Y |
29.9.3 | Three-dimensional hypotenuse | Y |
29.9.4 | Classification / comparison functions | Y |
29.9.5 | Mathematical special functions | Y |
30 | Input/output library
30.1 | General | Y |
30.2 | Iostreams requirements | Y |
30.2.1 | Imbue Limitations | Y |
30.2.2 | Positioning Type Limitations | Y |
30.2.3 | Thread safety | Partial |
30.3 | Forward declarations | Y |
30.4 | Standard iostream objects | Y |
30.5 | Iostreams base classes | Y |
30.6 | Stream buffers | Y |
30.7 | Formatting and manipulators | Y |
30.8 | String-based streams | Y |
30.9 | File-based streams | Y |
30.10 | File systemss | Y |
30.11 | C library files | Y |
31 | Regular expressions
31.1 | General | Y |
31.2 | Definitions | Y |
31.3 | Requirements | Y |
31.4 | Header `<regex>` synopsis | Y |
31.5 | Namespace `std::regex_constants` | Y |
31.6 | Class `regex_error` | Y |
31.7 | Class template `regex_traits` | Partial | `transform_primary` is not correctly implemented
31.8 | Class template `basic_regex` | Y |
31.9 | Class template `sub_match` | Y |
31.10 | Class template `match_results` | Y |
31.11 | Regular expression algorithms | Y |
31.12 | Regular expression Iterators | Y |
31.13 | Modified ECMAScript regular expression grammar | Y |
32 | Atomic operations
32.1 | General | Y |
32.2 | Header `<atomic>` synopsis | Y |
32.3 | Type aliases | Y |
32.4 | Order and consistency | Y |
32.5 | Lock-free property | Y |
32.6 | Class template `<atomic>` | Y |
32.7 | Non-member functions | Y |
32.8 | Flag Type and operations | Y |
32.9 | Fences | Y |
33 | Thread support
33.1 | General | Y |
33.2 | Requirements | Y |
33.3 | Threads |  |
33.3.1 | Header `thread` synopsis |  |
33.3.2 | Class `thread` | Y |
33.3.2.1 | Class `thread` | Partial | `thread::id` comparisons not well-defined
33.3.3 | Namespace `this_thread` | Y |
33.4 | Mutual exclusion |  |
33.4.3 | Mutex requirements |  |
33.4.3.1 | In general |  |
33.4.3.2 | Mutex types |  |
33.4.3.2.1 | Class `mutex` | Y |
33.4.3.2.2 | Class `recursive_mutex` | Y |
33.4.3.3 | Timed mutex types |  |
33.4.3.3.1 | Class `timed_mutex` | Y |
33.4.3.3.2 | Class `recursive_timed_mutex` | Y |
33.4.3.4 | Shared mutex types |  |
33.4.3.4.1 | Class `shared_mutex` | Y |
33.4.3.5 | Shared timed mutex types |  |
33.4.3.5.1 | Class `shared_timed_mutex` | Y |
33.4.4 | Locks |  |
33.4.4.1 | Class template `lock_guard` | Y |
33.4.4.2 | Class template `scoped_guard` | Y |
33.4.4.3 | Class template `unique_lock` | Y |
33.4.4.4 | Class template `shared_lock` | Y |
33.4.5 | Generic locking algorithms | Y |
33.4.6 | Call once |  |
33.4.6.1 | Struct `once_flag` | Y |
33.4.6.2 | Function `call_once` | Y | Exception support is broken. See PR 66146.
33.5 | Condition variables | Y |
33.5.1 | Class `condition_variable` | Y |
33.5.2 | Class `condition_variable_any` | Y |
33.6 | Futures |  |
33.6.1 | Overview |  |
33.6.2 | Header `<future>` |  |
33.6.3 | Error handling | Y |
33.6.4 | Class `future_error` | Y |
33.6.5 | Shared state | Y |
33.6.6 | Class template `promise` | Y |
33.6.7 | Class template `future` | Y |
33.6.8 | Class template `shared_future` | Y |
33.6.9 | Function template `async` | Y |
33.6.10 | Class template `packaged_task` | Y |
Appendix D | Compatibility features
D.4 | C++ standard library headers | Y |
D.4.1 | Header `<ccomplex>` synopsis | Y |
D.4.1 | Header `<cstdalign>` synopsis | Y |
D.4.1 | Header `<cstdbool>` synopsis | Y |
D.4.1 | Header `<ctgmath>` synopsis | Y |
D.5 | C standard library headers | Y |
D.6 | `char*` streams | Y |
D.7 | `uncaught_exception` | Y |
D.8 | Old adaptable function bindings | Y |
D.9 | The default allocator | Y |
D.10 | Raw storage iterator | Y |
D.11 | Temporary buffers | Y |
D.12 | Deprecated type traits | Y |
D.13 | Deprecated iterator primitives | Y |
D.14 | Deprecated `shared_ptr` observers | Y |
D.15 | Deprecated standard code conversion facets | Y |
D.16 | Deprecated convenience conversion interfaces | Y |

Table 1.7. C++ Technical Specifications Implementation Status

Paper | Title | Status | Comments
--- | --- | --- | ---
N4076 | A generalized callable negator | Y | Library Fundamentals 2 TS
N4273 | Uniform Container Erasure | Y | Library Fundamentals 2 TS
N4061 | Greatest Common Divisor and Least Common Multiple | Y | Library Fundamentals 2 TS
N4066 | Delimited iterators | Y | Library Fundamentals 2 TS
N4282 | The World's Dumbest Smart Pointer | Y | Library Fundamentals 2 TS
N4388 | Const-Propagating Wrapper | Y | Library Fundamentals 2 TS
N4391 | `make_array`, revision 4 | Y | Library Fundamentals 2 TS
N4502 | Support for the C++ Detection Idiom, V2 | Y | Library Fundamentals 2 TS
N4519 | Source-Code Information Capture | Y | Library Fundamentals 2 TS
N4521 | Merge Fundamentals V1 into V2 | N (components from V1 are still in namespace `fundamentals_v1`) | Library Fundamentals 2 TS
P0013R1 | Logical Operator Type Traits (revision 1) | Y | Library Fundamentals 2 TS
N4531 | std::rand replacement, revision 3 | Y | Library Fundamentals 2 TS
P0214R9 | Data-Parallel Types | Y | Parallelism 2 TS

#### Implementation Specific Behavior

For behaviour which is also specified by previous standards, see C++ 1998/2003 Implementation Specific Behavior and C++ 2011 Implementation Specific Behavior. This section only documents behaviour which is new in the 2017 standard.

20.5.1.2 [headers] Whether names from Annex K are declared by C++ headers depends on whether the underlying C library supports Annex K and declares the names. For the GNU C library, there is no Annex K support and so none of its names are declared by C++ headers.

23.6.5 [optional.bad_optional_access] `what()` returns `"bad optional access"`.

23.7.3 [variant.variant] `variant` supports over-aligned types.

23.7.10 [variant.bad.access] `what()` returns one of the strings `"std::get: variant is valueless"`, `"std::get: wrong index for variant"`, `"std::visit: variant is valueless"`, or `"std::visit<R>: variant is valueless"`.

23.8.2 [any.bad_any_cast] `what()` returns `"bad any_cast"`.

23.12.5 [mem.res.pool.options], 23.12.5 [mem.res.pool.mem] Let S equal `numeric_limits<size_t>::digits`. The limit for maximum number of blocks in a chunk is given by 2N-1, where N is min(19, 3 + S/2). The largest allocation size that will be allocated from a pool is 222 when S > 20, otherwise 3072 when S > 16, otherwise 768.

23.12.6.1 [mem.res.monotonic.buffer.ctor] The default `next_buffer_size` is `128 * sizeof(void*)`. The default growth factor is `1.5`.

23.15.4.3 [meta.unary.prop] The predicate condition for `has_unique_object_representations` is true for all scalar types except floating point types.

23.19.3 [execpol.type], 28.4.3 [algorithms.parallel.exec] There are no implementation-defined execution policies.

24.4.2 [string.view.template] `basic_string_view<C, T>::iterator` is `C*` and `basic_string_view<C, T>::const_iterator` is `const C*`.

28.4.3 [algorithms.parallel.exec] Threads of execution created by `std::thread` provide concurrent forward progress guarantees, so threads of execution implicitly created by the library will provide parallel forward progress guarantees.

29.4.1 [cfenv.syn] The effects of the `<cfenv>` functions depends on whether the `FENV_ACCESS` pragma is supported, and on the C library that provides the header.

29.6.9 [c.math.rand] Whether the `rand` function may introduce data races depends on the target C library that provides the function.

29.9.5 [sf.cmath] Calling the mathematical special functions with large inputs is supported but the results may be imprecise.

30.7.5.2.3 [ostream.inserters] NTCTS for `nullptr_t` is `"nullptr"`.

30.10.2.1 [fs.conform.9945], 30.10.2.2 [fs.conform.os] The behavior of the filesystem library implementation will depend on the target operating system. Some features will not be supported on some targets. Symbolic links and file permissions are not supported on Windows.

30.10.5 [fs.filesystem.syn] The clock used for file times is an unspecified type with a signed 64-bit representation, capable of representing timestamps with nanosecond resolution. The clock's epoch is unspecified, but is not the same as the system clock's epoch.

30.10.7.1 [fs.path.generic] dot-dot in the root-directory refers to the root-directory itself. On Windows, a drive specifier such as `"C:"` or `"z:"` is treated as a root-name. On Cygwin, a path that begins with two successive directory separators is a root-name. Otherwise (for POSIX-like systems other than Cygwin), the implementation-defined root-name is an unspecified string which does not appear in any pathnames.

30.10.10.1 [fs.enum.path.format] The character sequence is always interpreted in the native pathname format.

30.10.15.4 [fs.op.file_size] If `!is_regular_file(p)`, an error is reported.

30.10.15.32 [fs.op.rename] On Windows, `filesystem::rename` is implemented by calling `MoveFileExW` and so does not meet the requirements of POSIX `rename` when one or both of the paths resolves to an existing directory. Specifically, it is not possible to rename a directory to replace another directory (POSIX requires that to work if the directory being replaced is empty).

30.10.29.2 [fs.enum.file_type], 30.10.34.3 [fs.op.copy], 30.10.34.35 [fs.op.status] No additional file types are supported, and there are no implementation-defined enumerators in `std::filesystem::file_type`.

30.10.32 [fs.class.directory_iterator], 30.10.33 [fs.class.rec.dir.itr] Any directory-like file types supported by `opendir`/`readdir` (or `_wopendir`/`_wreaddir` on Windows).

##### Parallelism 2 TS

9.3 [parallel.simd.abi] `max_fixed_size<T>` is 32, except when targetting AVX512BW and `sizeof(T)` is 1.

When targeting 32-bit x86, `simd_abi::compatible<T>` is an alias for `simd_abi::scalar`. When targeting 64-bit x86 (including x32) or Aarch64, `simd_abi::compatible<T>` is an alias for `simd_abi::_VecBuiltin<16>`, unless `T` is `long double`, in which case it is an alias for `simd_abi::scalar`. When targeting ARM (but not Aarch64) with NEON support, `simd_abi::compatible<T>` is an alias for `simd_abi::_VecBuiltin<16>`, unless `sizeof(T) > 4`, in which case it is an alias for `simd_abi::scalar`. Additionally, `simd_abi::compatible<float>` is an alias for `simd_abi::scalar` unless compiling with -ffast-math.

When targeting x86 (both 32-bit and 64-bit), `simd_abi::native<T>` is an alias for one of `simd_abi::scalar`, `simd_abi::_VecBuiltin<16>`, `simd_abi::_VecBuiltin<32>`, or `simd_abi::_VecBltnBtmsk<64>`, depending on `T` and the machine options the compiler was invoked with.

When targeting ARM/Aarch64 or POWER, `simd_abi::native<T>` is an alias for `simd_abi::scalar` or `simd_abi::_VecBuiltin<16>`, depending on `T` and the machine options the compiler was invoked with.

For any other targeted machine `simd_abi::compatible<T>` and `simd_abi::native<T>` are aliases for `simd_abi::scalar`. (subject to change)

The extended ABI tag types defined in the `std::experimental::parallelism_v2::simd_abi` namespace are: `simd_abi::_VecBuiltin<Bytes>`, and `simd_abi::_VecBltnBtmsk<Bytes>`.

`simd_abi::deduce<T, N, Abis...>::type`, with `N > 1` is an alias for an extended ABI tag, if a supported extended ABI tag exists. Otherwise it is an alias for `simd_abi::fixed_size<N>`. The `simd_abi::_VecBltnBtmsk` ABI tag is preferred over `simd_abi::_VecBuiltin`.

9.4 [parallel.simd.traits] `memory_alignment<T, U>::value` is `sizeof(U) * T::size()` rounded up to the next power-of-two value.

9.6.1 [parallel.simd.overview] On ARM, `simd<T, _VecBuiltin<Bytes>>` is supported if `__ARM_NEON` is defined and `sizeof(T) <= 4`. Additionally, `sizeof(T) == 8` with integral `T` is supported if `__ARM_ARCH >= 8`, and `double` is supported if `__aarch64__` is defined. On POWER, `simd<T, _VecBuiltin<Bytes>>` is supported if `__ALTIVEC__` is defined and `sizeof(T) < 8`. Additionally, `double` is supported if `__VSX__` is defined, and any `T` with `sizeof(T) <= 8` is supported if `__POWER8_VECTOR__` is defined. On x86, given an extended ABI tag `Abi`, `simd<T, Abi>` is supported according to the following table:

Table 1.8. Support for Extended ABI Tags

ABI tag `Abi` | value type `T` | values for `Bytes` | required machine option
--- | --- | --- | ---
`_VecBuiltin<Bytes>` | `float` | 8, 12, 16 | "-msse"
20, 24, 28, 32 | "-mavx"
`double` | 16 | "-msse2"
24, 32 | "-mavx"
integral types other than `bool` | `Bytes` ≤ 16 and `Bytes` divisible by `sizeof(T)` | "-msse2"
16 < `Bytes` ≤ 32 and `Bytes` divisible by `sizeof(T)` | "-mavx2"
`_VecBuiltin<Bytes>` and `_VecBltnBtmsk<Bytes>` | vectorizable types with `sizeof(T)` ≥ 4 | 32 < `Bytes` ≤ 64 and `Bytes` divisible by `sizeof(T)` | "-mavx512f"
vectorizable types with `sizeof(T)` < 4 | "-mavx512bw"
`_VecBltnBtmsk<Bytes>` | vectorizable types with `sizeof(T)` ≥ 4 | `Bytes` ≤ 32 and `Bytes` divisible by `sizeof(T)` | "-mavx512vl"
vectorizable types with `sizeof(T)` < 4 | "-mavx512bw" and "-mavx512vl"

### C++ 2020

In this implementation the `-std=gnu++20` or `-std=c++20` flag must be used to enable language and library features. See dialect options. The pre-defined symbol `__cplusplus` is used to check for the presence of the required flag.

This section describes the C++20 and library TS support in mainline GCC, not in any particular release.

The following table lists new library features that are included in the C++20 standard. The "Proposal" column provides a link to the ISO C++ committee proposal that describes the feature, while the "Status" column indicates the first version of GCC that contains an implementation of this feature (if it has been implemented). A dash (—) in the status column indicates that the changes in the proposal either do not affect the code in libstdc++, or the changes are not required for conformance. The "SD-6 Feature Test / Notes" column shows the corresponding macro or header from SD-6: Feature-testing recommendations for C++ (where applicable) or any notes about the implementation.

Table 1.9. C++ 2020 Library Features

Library Feature | Proposal | Status | SD-6 Feature Test / Notes
--- | --- | --- | ---
Compile-time programming
Add constexpr modifiers to functions in `<algorithm>` and `<utility>` Headers | P0202R3 | 10.1 | `__cpp_lib_constexpr_algorithms >= 201703L`
Constexpr for `swap` and swap related functions | P0879R0 | 10.1 | `__cpp_lib_constexpr_algorithms >= 201806L`
Constexpr for `std::complex` | P0415R1 | 9.1 | `__cpp_lib_constexpr_complex >= 201711L` (since 9.4, see Note 1)
`std::is_constant_evaluated()` | P0595R2 | 9.1 | `__cpp_lib_is_constant_evaluated >= 201811L`
More constexpr containers | P0784R7 | 10.1 | `__cpp_lib_constexpr_dynamic_alloc >= 201907L`
Making `std::string` constexpr | P0980R1 | 12.1 | `__cpp_lib_constexpr_string >= 201907L`
Making `std::vector` constexpr | P1004R2 | 12.1 | `__cpp_lib_constexpr_vector >= 201907L`
Constexpr in `std::pointer_traits` | P1006R1 | 9.1 | `__cpp_lib_constexpr_memory >= 201811L` (since 9.4, see Note 1)
constexpr for `<numeric>` algorithms | P1645R1 | 10.1 | `__cpp_lib_constexpr_numeric >= 201911L`
Constexpr iterator requirements | P0858R0 | 9.1 |
`__cpp_lib_array_constexpr >= 201803L`
`__cpp_lib_string_view >= 201803L`
(both since 9.4, see Note 1)
`constexpr` comparison operators for `std::array` | P1023R0 | 10.1 | `__cpp_lib_array_constexpr >= 201806`
Misc constexpr bits | P1032R1 | 10.1 |
`__cpp_lib_array_constexpr >= 201811L`
`__cpp_lib_constexpr_functional >= 201811L`
`__cpp_lib_constexpr_iterator >= 201811L`
`__cpp_lib_constexpr_string_view >= 201811L`
`__cpp_lib_constexpr_tuple >= 201811L`
`__cpp_lib_constexpr_utility >= 201811L`
`constexpr INVOKE` | P1065R2 | 10.1 | `__cpp_lib_constexpr_functional >= 201907L`
Transformation Trait `remove_cvref` | P0550R2 | 9.1 | `__cpp_lib_remove_cvref >= 201711L` (since 9.4, see Note 1)
Implicit conversion traits and utility functions | P0758R1 | 9.1 | `__cpp_lib_is_nothrow_convertible >= 201806L` (since 9.4, see Note 1)
The `identity` metafunction | P0887R1 | 9.1 | `__cpp_lib_type_identity >= 201806L` (since 9.4, see Note 1)
`unwrap_ref_decay` and `unwrap_reference` | P0318R1 | 9.1 | `__cpp_lib_unwrap_ref >= 201811L` (since 9.4, see Note 1)
Improving Completeness Requirements for Type Traits | P1285R0 | — | Most misuses are diagnosed, but not all.
Missing feature test macros | P1353R0 | 9.1 |
Making std::underlying_type SFINAE-friendly | P0340R3 | 9.1 |
Traits for [Un]bounded Arrays | P1357R1 | 9.1 | `__cpp_lib_bounded_array_traits >= 201902L`
Layout-compatibility and pointer-interconvertibility traits | P0466R5 | 12.1 |
`__cpp_lib_is_layout_compatible >= 201907L`
`__cpp_lib_is_pointer_interconvertible >= 201907L`
Integrating feature-test macros into the C++ WD | P0941R2 | 5.1 |
`<version>` | P0754R2 | 9.1 | `__has_include(<version>)`
Synchronization
Atomic Ref | P0019R8 | 10.1 | `__cpp_lib_atomic_ref >= 201806L`
Floating Point Atomic | P0020R6 | 10.1 | `__cpp_lib_atomic_float >= 201711L`
C++ Synchronized Buffered Ostream | P0053R7 | 11.1 | `__cpp_lib_syncbuf >= 201711L`
Manipulators for C++ Synchronized Buffered Ostream | P0753R2 | 11.1 | `__cpp_lib_syncbuf >= 201803L`
Make `std::memory_order` a scoped enumeration | P0439R0 | 9.1 |
The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange | P0528R3 | 13.1 |
Atomic `shared_ptr` | P0718R2 | 12.1 | `__cpp_lib_atomic_shared_ptr >= 201711L`
std::stop_token and std::jthread | P0660R10 | 10.1 | `__cpp_lib_jthread >= 201907L`
Rename `condition_variable_any` interruptible wait methods | P1869R1 | 10.1 | `__cpp_lib_jthread >= 201911L`
Atomic waiting and notifying, std::semaphore, std::latch and std::barrier | P1135R6 | 11.1 |
`__cpp_lib_atomic_lock_free_type_aliases >= 201907L`
`__cpp_lib_atomic_flag_test >= 201907L`
`__cpp_lib_atomic_wait >= 201907L`
`__cpp_lib_semaphore >= 201907L`
`__cpp_lib_latch >= 201907L`
`__cpp_lib_barrier >= 201907L`
Fixing Atomic Initialization | P0883R2 | 10.1 | `__cpp_lib_atomic_value_initialization >= 201911L`
Ranges and Concepts
Standard Library Concepts | P0898R3 | 10.1 | `__cpp_lib_concepts >= 201806L`
Rename concepts to standard_case for C++20, while we still can | P1754R1 | 10.1 | `__cpp_lib_concepts >= 201907L`
Wording for `boolean-testable` | P1964R2 | 10.1 | `__cpp_lib_concepts >= 202002L`
The One Ranges Proposal | P0896R4 | 10.1 | `__cpp_lib_ranges >= 201811L`
Input Range Adaptors | P1035R7 | 10.1 | `__cpp_lib_ranges >= 201907L`
`ranges` compare algorithm are over-constrained | P1716R3 | 10.1 | `__cpp_lib_ranges >= 201911L`
Remove CommonReference requirement from StrictWeakOrdering (a.k.a Fixing Relations) | P1248R1 | 10.1 |
Ranges Design Cleanup | P1252R2 | 10.1 |
Avoid template bloat for `safe_ranges` in combination with ‘subrange-y’ view adaptors. | P1739R4 | 12.1 |
Time, dates, calendars, time zones
Extending chrono to Calendars and Time Zones | P0355R7 | 14.1 (see Note 2) | `__cpp_lib_chrono >= 201803L`
Miscellaneous minor fixes for chrono | P1466R3 | 11.1 (see Note 2) | `__cpp_lib_chrono >= 201907L`
`<chrono>` `zero()`, `min()`, and `max()` should be `noexcept` | P0972R0 | 9.1 |
Three-way comparison
Library Support for the Spaceship (Comparison) Operator | P0768R1 | 10.1 | `__cpp_lib_three_way_comparison >= 201711L`
Symmetry for spaceship | P0905R1 | 10.1 |
Adding <=> to the standard library | P1614R2 | 10.1 | `__cpp_lib_three_way_comparison >= 201907L`
Strings and text
`string::reserve` Should Not Shrink | P0966R1 | 11.1 |
`char8_t`: A type for UTF-8 characters and strings | P0482R6 | 9.1 | `__cpp_lib_char8_t >= 201811L`
`char8_t` backward compatibility remediation | P1423R3 | 10.1 | `__cpp_lib_char8_t >= 201907L`
Text formatting | P0645R10 | 13.1 | `__cpp_lib_format >= 201907L`
Integration of chrono with text formatting | P1361R2 | 13.1 | `__cpp_lib_format >= 201907L`
Printf corner cases in `std::format` | P1652R1 | 13.1 | `__cpp_lib_format >= 201907L`
String Prefix and Suffix Checking | P0457R2 | 9.1 | `__cpp_lib_starts_ends_with >= 201711L` (since 9.4, see Note 1)
Update The Reference To The Unicode Standard | P1025R1 | — |
Containers
span: bounds-safe views for sequences of objects | P0122R7 | 10.1 | `__cpp_lib_span >= 201803L`
Usability Enhancements for `std::span` | P1024R3 | 10.1 | `__cpp_lib_span >= 201902L`
Should Span be Regular? | P1085R2 | 10.1 |
Fixed-size `<span>` construction from dynamic range | P1976R2 | 10.1 | `__cpp_lib_span >= 202002L`
`std::to_array` | P0325R4 | 10.1 | `__cpp_lib_to_array >= 201907L`
Checking for Existence of an Element in Associative Containers | P0458R2 | 9.1 |
Comparing Unordered Containers | P0809R0 | — |
Heterogeneous lookup for unordered containers | P0919R3 | 11.1 | `__cpp_lib_generic_unordered_lookup >= 201811`
Refinement Proposal for P0919 | P1690R1 | 11.1 |
Adopt Consistent Container Erasure from Library Fundamentals 2 for C++20 | P1209R0 | 9.1 | `__cpp_lib_erase_if >= 201811L`
Improving the Return Value of Erase-Like Algorithms | P0646R1 | 9.1 | `__cpp_lib_list_remove_return_type >= 201806L`
Improving the Return Value of Erase-Like Algorithms II: Free `erase`/`erase_if` | P1115R3 | 9.1 |
`__cpp_lib_erase_if >= 202002L`
(defined to `201900L` for GCC 9.1 and 9.2 so use `> 201811L`)
Signed ssize() functions, unsigned size() functions | P1227R2 | 10.1 | `__cpp_lib_ssize >= 201902L`
Memory management
Utility to convert a pointer to a raw pointer | P0653R2 | 8.1 | `__cpp_lib_to_address >= 201711L` (since 9.4, see Note 1)
Extending `make_shared` to Support Arrays | P0674R1 | 12.1 | `__cpp_lib_shared_ptr_arrays >= 201707L`
Efficient sized delete for variable sized classes | P0722R3 | 9.1 | `__cpp_lib_destroying_delete >= 201806L`
Utility functions to implement uses-allocator construction | P0591R4 | 9.1 | `std::scoped_allocator_adaptor` changes missing in 9.1.0
`std::assume_aligned` | P1007R3 | 9.1 | `__cpp_lib_assume_aligned >= 201811L` (since 9.4, see Note 1)
Smart pointer creation with default initialization | P1020R1 | 12.1 | `__cpp_lib_smart_ptr_for_overwrite >= 201811L`
Rename "default_init" Functions | P1973R1 | 12.1 | `__cpp_lib_smart_ptr_for_overwrite >= 201811L`
Make stateful allocator propagation more consistent for `operator+(basic_string)` | P1165R1 | 10.1 |
`polymorphic_allocator<>` as a vocabulary type | P0339R6 | 9.1 | `__cpp_lib_polymorphic_allocator >= 201902L` (since 9.4, see Note 1)
LWG 2511: guaranteed copy elision for piecewise construction | P0475R1 | 7.1 |
Miscellaneous
`nodiscard` in the Library | P0600R1 | 9.1 |
de-pessimize legacy algorithms with `std::move` | P0616R0 | 9.1 |
Deprecate POD | P0767R1 | 10.1 |
Treating Unnecessary `decay` | P0777R1 | 9.1 |
Thou Shalt Not Specialize std Function Templates! | P0551R3 |  | These changes will not be implemented.
Bit-casting object representations | P0476R2 | 11.1 | `__cpp_lib_bit_cast >= 201806L`
Integral power-of-2 operations | P0556R3 | 9.1 | `__cpp_lib_int_pow2 >= 201806L` (since 9.4, see Note 1)
On the names of low-level bit manipulation functions | P1956R1 | 10.1 | `__cpp_lib_int_pow2 >= 202002L`
Safe integral comparisons | P0586R2 | 10.1 | `__cpp_lib_integer_comparison_functions >= 202002L`
Reviewing Deprecated Facilities of C++17 for C++20 | P0619R4 | 12.1 |
`fpos` Requirements | P0759R1 | — |
Add `shift` to `<algorithm>` | P0769R2 | 10.1 | `__cpp_lib_shift >= 201806L`
Standard Library Specification in a Concepts and Contracts World | P0788R3 | — |
`explicit(bool)` | P0892R2 | — |
Eradicating unnecessarily explicit default constructors from the standard library | P0935R0 | 9.1 |
`std::function` move constructor should be `noexcept` | P0771R1 | 7.2 |
Simplified partial function application | P0356R5 | 9.1 | `__cpp_lib_bind_front >= 201811L`
`bind_front` should not unwrap `reference_wrapper` | P1651R0 | 9.3 | `__cpp_lib_bind_front >= 201907L`
`reference_wrapper` for incomplete types | P0357R3 | 9.1 |
Fixing `operator>>(basic_istream&, CharT*)` (LWG 2499) | P0487R1 | 11.1 |
`variant` and `optional` should propagate copy/move triviality | P0602R4 | 8.3 |
A sane `variant` converting constructor | P0608R3 | 10.1 |
`visit<R>`: Explicit Return Type for `visit` | P0655R1 | 9.1 |
P0899R1 - LWG 3016 is not a defect | P0899R1 | 7.1 |
Editorial Guidance for merging P0019r8 and P0528r3 | P1123R0 | — |
Cleaning up Clause 20 | P1148R0 | — |
Completing the Rebase of Library Fundamentals, Version 3, Working Draft | P1210R0 |  |
Alternative Wording for P0907R4 Signed Integers are Two's Complement | P1236R1 | — |
I Stream, You Stream, We All Stream for `istream_iterator` | P0738R2 | 10.1 |
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 21 - Containers library | P1463R1 | 10.1 |
Mandating the Standard Library: Clause 22 - Iterators library | P1464R1 | — |
Make `create_directory()` Intuitive | P1164R1 | 8.3 | Treated as a DR for C++17
Target Vectorization Policies from Parallelism V2 TS to C++20 | P1001R2 | 9.1 | `__cpp_lib_execution >= 201902L` (since 9.4, see Note 1)
Merge Coroutines TS into C++20 working draft | P0912R5 | 10.1 | `__cpp_lib_coroutines >= 201902L`
Endian just Endian | P0463R1 | 8.1 | `__cpp_lib_endian >= 201907L`
Bit operations | P0553R4 | 9.1 | `__cpp_lib_bitops >= 201907L` (since 9.4, see Note 1)
Well-behaved interpolation for numbers and pointers | P0811R3 | 9.1 | `__cpp_lib_interpolate >= 201902L`
Mathematical constants | P0631R8 | 10.1 | `__cpp_lib_math_constants >= 201907L`
std::source_location | P1208R6 | 11.1 | `__cpp_lib_source_location >= 201907L`
Efficient access to std::basic_stringbuf's Buffer | P0408R7 | 11.1 |

Note 1: This feature is supported in older releases but the `__cpp_lib` macro is not defined to the right value (or not defined at all) until the version shown in parentheses.

Note 2: The C++20 calendar types are supported since 11.1, time zones and UTC are supported since 13.1, and `chrono::parse` is supported since 14.1.

The following status table is based on the table of contents of ISO/IEC 14882:2020. Some subclauses are not shown in the table where the content is unchanged since C++17 and the implementation is complete.

Table 1.10. C++ 2020 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
17 | Language support library
17.1 | General |  |
17.2 | Common definitions |  |
17.2.1 | Header `<cstddef>` synopsis | Y |
17.2.2 | Header `<cstdlib>` synopsis | Y |
17.2.3 | Null pointers | Y |
17.2.4 | Sizes, alignments, and offsets | Y |
17.2.5 | `byte` type operations | Y |
17.3 | Implementation properties |  |
17.3.1 | General |  |
17.3.2 | Header `<version>` synopsis | Y |
17.3.3 | Header `<limits>` synopsis | Y |
17.3.4 | Floating-point type properties |  |
17.3.4.1 | Type `float_round_style` | N |
17.3.4.2 | Type `float_denorm_style` | N |
17.3.5 | Class template `numeric_limits` | Y |
17.3.6 | Header `<climits>` synopsis | Y |
17.3.7 | Header `<cfloat>` synopsis | Y |
17.4 | Integer types |  |
17.4.1 | General |  |
17.4.2 | Header `<cstdint>` synopsis | Y |
17.5 | Startup and termination | Partial | C library dependency for quick_exit, at_quick_exit
17.6 | Dynamic memory management | Y |
17.7 | Type identification | Y |
17.8 | Source location |  |
17.8.1 | Header `<source_location>` synopsis | Y |
17.8.2 | Class `source_location` | Y |
17.9 | Exception handling | Y |
17.10 | Initializer lists | Y |
17.11 | Comparisons |  |
17.11.1 | Header `<compare>` synopsis | Y |
17.11.2 | Comparison category types | Y |
17.11.3 | Class template `common_comparison_category` | Y |
17.11.4 | Concept `three_way_comparable` | Y |
17.11.5 | Result of three-way comparison | Y |
17.11.6 | Comparison algorithms | Y |
17.12 | Coroutines |  |
17.12.1 | General |  |
17.12.2 | Header `<coroutine>` synopsis | Y |
17.12.3 | Coroutine traits | Y |
17.12.4 | Class template `coroutine_handle` | Y |
17.12.5 | No-op coroutines | Y |
17.13 | Other runtime support | Y |
18 | Concepts library
18.1 | General |  |
18.2 | Equality preservation |  |
18.3 | Header `<concepts>` synopsis | Y |
18.4 | Language-related concepts |  |
18.4.1 | General |  |
18.4.2 | Concept `same_as` | Y |
18.4.3 | Concept `derived_from` | Y |
18.4.4 | Concept `convertible_to` | Y |
18.4.5 | Concept `common_reference_with` | Y |
18.4.6 | Concept `common_with` | Y |
18.4.7 | Arithmetic concepts |  |
18.4.8 | Concept `assignable_from` | Y |
18.4.9 | Concept `swappable` | Y |
18.4.10 | Concept `destructible` | Y |
18.4.11 | Concept `constructible_from` | Y |
18.4.12 | Concept `default_initializable` | Y |
18.4.13 | Concept `move_constructible` | Y |
18.4.14 | Concept `copy_constructible` | Y |
18.5 | Comparison concepts |  |
18.5.1 | General |  |
18.5.2 | Boolean testability | Y |
18.5.3 | Concept `equality_comparable` | Y |
18.5.4 | Concept `totally_ordered` | Y |
18.6 | Object concepts | Y |
18.7 | Callable concepts |  |
18.7.1 | General |  |
18.7.2 | Concept `invocable` | Y |
18.7.3 | Concept `regular_invocable` | Y |
18.7.4 | Concept `predicate` | Y |
18.7.5 | Concept `relation` | Y |
18.7.6 | Concept `equivalence_relation` | Y |
18.7.7 | Concept `strict_weak_order` | Y |
19 | Diagnostics library
19.1 | General |  |
19.2 | Exception classes | Y |
19.3 | Assertions | Y |
19.4 | Error numbers | Y |
19.5 | System error support |  |
19.5.1 | General |  |
19.5.2 | Header `<system_error>` synopsis | Y |
19.5.3 | Class `error_category` | Y |
19.5.4 | Class `error_code` | Y |
19.5.5 | Class `error_condition` | Y |
19.5.6 | Comparison operator functions | Y |
19.5.7 | System error hash support | Y |
19.5.8 | Class `system_error` | Y |
20 | General utilities library
20.1 | General |  |
20.2 | Utility components |  |
20.2.1 | Header `<utility>` synopsis | Y |
20.2.2 | `swap` | Y |
20.2.3 | `exchange` | Y |
20.2.4 | Forward/move helpers | Y |
20.2.5 | Function template `as_const` | Y |
20.2.6 | Function template `declval` | Y |
20.2.7 | Integer comparison functions | Y |
20.3 | Compile-time integer sequences | Y |
20.4 | Pairs | Y |
20.5 | Tuples | Y |
20.6 | Optional objects | Y |
20.7 | Variants | Y |
20.8 | Storage for any type | Y |
20.9 | Bitsets | Y |
20.10 | Memory | Y |
20.11 | Smart pointers |  |
20.11.1 | Class template `unique_ptr` | Y |
20.11.2 | Class `bad_weak_ptr` | Y |
20.11.3 | Class template `shared_ptr` | Y | Uses code from boost::shared_ptr.
20.11.4 | Class template `weak_ptr` | Y |
20.11.5 | Class template `owner_less` | Y |
20.11.6 | Class template `enable_shared_from_this` | Y |
20.11.7 | Smart pointer hash support | Y |
20.12 | Memory resources |  |
20.12.1 | Header `<memory_resource>` synopsis | Y |
20.12.2 | Class `memory_resource` | Y |
20.12.3 | Class template `polymorphic_allocator` | Y |
20.12.4 | Access to program-wide `memory_resource` objects | Y |
20.12.5 | Pool resource classes | Y |
20.12.6 | Class `monotonic_buffer_resource` | Y |
20.13 | Class template `scoped_allocator_adaptor` | Y |
20.14 | Function objects |  |
20.14.1 | General |  |
20.14.2 | Header `<functional>` synopsis | Y |
20.14.3 | Definitions |  |
20.14.4 | Requirements |  |
20.14.5 | Function template `invoke` | Y |
20.14.6 | Class template `reference_wrapper` | Y |
20.14.7 | Arithmetic operations | Y |
20.14.8 | Comparisons | Y |
20.14.9 | Concept-constrained comparisons | Y |
20.14.10 | Logical operations | Y |
20.14.11 | Bitwise operations | Y |
20.14.12 | Class `identity` | Y |
20.14.13 | Function template `not_fn` | Y |
20.14.14 | Function template `bind_front` | Y |
20.14.15 | Function object binders | Y |
20.14.16 | Function template `mem_fn` | Y |
20.14.17 | Polymorphic function wrappers |  |
20.14.17.1 | General |  |
20.14.17.2 | Class `bad_function_call` | Y |
20.14.17.3 | Class template `function` | Y |
20.14.18 | Searchers | Y |
20.15 | Metaprogramming and type traits |  |
20.15.1 | General |  |
20.15.2 | Requirements | Y |
20.15.3 | Header `<type_traits>` synopsis | Y |
20.15.4 | Helper classes | Y |
20.15.5 | Unary type traits | Y |
20.15.6 | Type property queries | Y |
20.15.7 | Relationships between types | Y |
20.15.8 | Transformations between types | Y |
20.15.9 | Logical operator traits | Y |
20.15.10 | Member relationships | Y |
20.15.11 | Constant evaluation context | Y |
20.16 | Compile-time rational arithmetic | Y |
20.17 | Class `type_index` | Y |
20.18 | Execution policies | Y |
20.19 | Primitive numeric conversions |  |
20.19.1 | Header `<charconv>` synopsis | Y |
20.19.2 | Primitive numeric output conversion | Y | Floating-point types up to 64-bit are formatted using Ryu. Types with greater precision are formatted using the C library (`sprintf` and conditionally `strfromf128`). For powerpc64le-unknown-linux-gnu `__sprintfieee128` must be provided by Glibc.
20.19.3 | Primitive numeric input conversion | Y | Floating-point types up to 64-bit are parsed using fast_float. Types with greater precision are parsed using the C library (`strtold`). For powerpc64le-unknown-linux-gnu `__strtoieee128` must be provided by Glibc.
20.20 | Formatting |  |
20.20.1 | Header `<format>` synopsis | Y |
20.20.2 | Format string |  |
20.20.2.1 | In general | Y |
20.20.2.2 | Standard format specifiers | Y |
20.20.3 | Error reporting | Y |
20.20.4 | Formatting functions | Y |
20.20.5 | Formatter | Y |
20.20.5.1 | Formatter requirements |  |
20.20.5.2 | Formatter specializations | Y |
20.20.5.3 | Class template `basic_format_parse_context` | Y |
20.20.5.4 | Class template `basic_format_context` | Y |
20.20.6 | Arguments |  |
20.20.6.1 | Class template `basic_format_arg` | Y |
20.20.6.2 | Class template format-arg-store | Y |
20.20.6.3 | Class template `basic_format_args` | Y |
20.20.7 | Class `format_error` | Y |
21 | Strings library
21.1 | General |  |
21.2 | Character traits | Y |
21.3 | String classes | Y |
21.4 | String view classes | Y |
21.5 | Null-terminated sequence utilities | Partial | C library dependency.
22 | Containers library
22.1 | General |  |
22.2 | Container requirements | Y |
22.3 | Sequence containers | Y |
22.4 | Associative containers | Y |
22.5 | Unordered associative containers | Y |
22.6 | Container adaptors | Y |
22.7 | Views |  |
22.7.1 | General |  |
22.7.2 | Header `<span>` synopsis | Y |
22.7.3 | Class template `span` | Y |
23 | Iterators library
23.1 | General |  |
23.2 | Header `<iterator>` synopsis | Y |
23.3 | Iterator requirements |  |
23.3.1 | In general | Y |
23.3.2 | Associated types | Y |
23.3.3 | Customization points | Y |
23.3.4 | Iterator concepts | Y |
23.3.5 | C++17 iterator requirements | Y |
23.3.6 | Indirect callable requirements | Y |
23.3.7 | Common algorithm requirements | Y |
23.4 | Iterator primitives |  |
23.4.1 | General |  |
23.4.2 | Standard iterator tags | Y |
23.4.3 | Iterator operations | Y |
23.4.4 | Range iterator operations | Y |
23.5 | Iterator adaptors |  |
23.5.1 | Reverse iterators | Y |
23.5.2 | Insert iterators | Y |
23.5.3 | Move iterators and sentinels | Y |
23.5.4 | Common iterators | Y |
23.5.5 | Default sentinel | Y |
23.5.6 | Counted iterators | Y |
23.5.7 | Unreachable sentinel | Y |
23.6 | Stream iterators | Y |
23.6.1 | General |  |
23.6.2 | Class template `istream_iterator` | Y |
23.6.3 | Class template `ostream_iterator` | Y |
23.6.4 | Class template `istreambuf_iterator` | Y |
23.6.5 | Class template `ostreambuf_iterator` | Y |
23.7 | Range access | Y |
24 | Ranges library
24.1 | General |  |
24.2 | Header `<ranges>` synopsis | Y |
24.3 | Range access | Y |
24.4 | Range requirements |  |
24.4.1 | General |  |
24.4.2 | Ranges | Y |
24.4.3 | Sized ranges | Y |
24.4.4 | Views | Y |
24.4.5 | Other range refinements | Y |
24.5 | Range utilities |  |
24.5.1 | General |  |
24.5.2 | Helper concepts | Y |
24.5.3 | View interface | Y |
24.5.4 | Sub-ranges | Y |
24.5.5 | Dangling iterator handling | Y |
24.6 | Range factories |  |
24.6.1 | General |  |
24.6.2 | Empty view | Y |
24.6.3 | Single view | Y |
24.6.4 | Iota view | Y |
24.6.5 | Istream view | Y |
24.7 | Range adaptors |  |
24.7.1 | General |  |
24.7.2 | Range adaptor objects | Y |
24.7.3 | Semiregular wrapper | Y |
24.7.4 | All view | Y |
24.7.5 | Filter view | Y |
24.7.6 | Transform view | Y |
24.7.7 | Take view | Y |
24.7.8 | Take while view | Y |
24.7.9 | Drop view | Y |
24.7.10 | Drop while view | Y |
24.7.11 | Join view | Y |
24.7.12 | Split view | Y |
24.7.13 | Counted view | Y |
24.7.14 | Common view | Y |
24.7.15 | Reverse view | Y |
24.7.16 | Elements view | Y |
25 | Algorithms library
25.1 | General |  |
25.2 | Algorithms requirements | Y |
25.3 | Parallel algorithms |  | Uses code from oneDPL
25.4 | Header `<algorithm>` synopsis | Y |
25.5 | Algorithm result types | Y |
25.6 | Non-modifying sequence operations |  |
25.6.1 | All of | Y |
25.6.2 | Any of | Y |
25.6.3 | None of | Y |
25.6.4 | For each | Y |
25.6.5 | Find | Y |
25.6.6 | Find end | Y |
25.6.7 | Find first | Y |
25.6.8 | Adjacent find | Y |
25.6.9 | Count | Y |
25.6.10 | Mismatch | Y |
25.6.11 | Equal | Y |
25.6.12 | Is permutation | Y |
25.6.13 | Search | Y |
25.7 | Mutating sequence operations |  |
25.7.1 | Copy | Y |
25.7.2 | Move | Y |
25.7.3 | Swap | Y |
25.7.4 | Transform | Y |
25.7.5 | Replace | Y |
25.7.6 | Fill | Y |
25.7.7 | Generate | Y |
25.7.8 | Remove | Y |
25.7.9 | Unique | Y |
25.7.10 | Reverse | Y |
25.7.11 | Rotate | Y |
25.7.12 | Sample | Y |
25.7.13 | Shuffle | Y |
25.7.14 | Shift | Y |
25.8 | Sorting and related operations |  |
25.8.1 | General | Y |
25.8.2 | Sorting | Y |
25.8.3 | Nth element | Y |
25.8.4 | Binary search | Y |
25.8.5 | Partitions | Y |
25.8.6 | Merge | Y |
25.8.7 | Set operations on sorted structures | Y |
25.8.8 | Heap operations | Y |
25.8.9 | Minimum and maximum | Y |
25.8.10 | Bounded value | Y |
25.8.11 | Lexicographical comparison | Y |
25.8.12 | Three-way comparison algorithms | Y |
25.8.13 | Permutation generators | Y |
25.9 | Header `<numeric>` synopsis | Y |
25.10 | Generalized numeric operations |  |
25.10.1 | General |  |
25.10.2 | Definitions |  |
25.10.3 | Accumulate | Y |
25.10.4 | Reduce | Y |
25.10.5 | Inner product | Y |
25.10.6 | Transform reduce | Y |
25.10.7 | Partial sum | Y |
25.10.8 | Exclusive scan | Y |
25.10.9 | Inclusive scan | Y |
25.10.10 | Transform exclusive scan | Y |
25.10.11 | Transform inclusive scan | Y |
25.10.12 | Adjacent difference | Y |
25.10.13 | Iota | Y |
25.10.14 | Greatest common divisor | Y |
25.10.15 | Least common multiple | Y |
25.10.16 | Midpoint | Y |
25.11 | Specialized `<memory>` algorithms |  |
25.11.1 | General |  |
25.11.2 | Special memory concepts | Y |
25.11.3 | `uninitialized_default_construct` | Y |
25.11.4 | `uninitialized_value_construct` | Y |
25.11.5 | `uninitialized_copy` | Y |
25.11.6 | `uninitialized_move` | Y |
25.11.7 | `uninitialized_fill` | Y |
25.11.8 | `construct_at` | Y |
25.11.9 | `destroy` | Y |
25.12 | C library algorithms | Y |
26 | Numerics library
26.1 | General |  |
26.2 | Numeric type requirements | Y |
26.3 | The floating-point environment | Y |
26.4 | Complex numbers | Y |
26.5 | Bit manipulation |  |
26.5.1 | General |  |
26.5.2 | Header `<bit>` synopsis | Y |
26.5.3 | Function template `bit_cast` | Y |
26.5.4 | Integral powers of 2 | Y |
26.5.5 | Rotating | Y |
26.5.6 | Counting | Y |
26.5.7 | Endian | Y |
26.6 | Random number generation | Y |
26.7 | Numeric arrays | Y |
26.8 | Mathematical functions for floating-point types | Y |
26.9 | Numbers |  |
26.9.1 | Header `<numbers>` synopsis | Y |
26.9.2 | Mathematical constants | Y |
27 | Time library
27.1 | General |  |
27.2 | Header `<chrono>` synopsis | Y |
27.3 | Cpp17Clock requirements | Y |
27.4 | Time-related traits |  |
27.4.1 | `treat_as_floating_point` | Y |
27.4.2 | `duration_values` | Y |
27.4.3 | Specializations of `common_type` | Y |
27.4.4 | Class template `is_clock` | Y |
27.5 | Class template `duration` |  |
27.5.1 | General | Y |
27.5.2 | Constructors | Y |
27.5.3 | Observer | Y |
27.5.4 | Arithmetic | Y |
27.5.5 | Special values | Y |
27.5.6 | Non-member arithmetic | Y |
27.5.7 | Comparisons | Y |
27.5.8 | Conversions | Y |
27.5.9 | Suffixes for duration literals | Y |
27.5.10 | Algorithms | Y |
27.5.11 | I/O | Y |
27.6 | Class template `time_point` | Y |
27.7 | Clocks |  |
27.7.1 | General | Y |
27.7.2 | Class `system_clock` | Y |
27.7.3 | Class `utc_clock` | Y |
27.7.4 | Class `tai_clock` | Y |
27.7.5 | Class `gps_clock` | Y |
27.7.6 | Type `file_clock` | Y |
27.7.7 | Class `steady_clock` | Y |
27.7.8 | Class `high_resolution_clock` | Y |
27.7.9 | Local time | Y |
27.7.10 | `time_point` conversions | Y |
27.8 | The civil calendar |  |
27.8.1 | In general |  |
27.8.2 | Class `last_spec` | Y |
27.8.3 | Class `day` | Y |
27.8.4 | Class `month` | Y |
27.8.5 | Class `year` | Y |
27.8.6 | Class `weekday` | Y |
27.8.7 | Class `weekday_indexed` | Y |
27.8.8 | Class `weekday_last` | Y |
27.8.9 | Class `month_day` | Y |
27.8.10 | Class `month_day_last` | Y |
27.8.11 | Class `month_weekday` | Y |
27.8.12 | Class `month_weekday_last` | Y |
27.8.13 | Class `year_month` | Y |
27.8.14 | Class `year_month_day` | Y |
27.8.15 | Class `year_month_day_last` | Y |
27.8.16 | Class `year_month_weekday` | Y |
27.8.17 | Class `year_month_weekday_last` | Y |
27.9 | Class template `hh_mm_ss` | Y |
27.10 | 12/24 hours functions | Y |
27.11 | Time zones |  |
27.11.1 | In general |  |
27.11.2 | Time zone database | Y |
27.11.3 | Exception classes | Y |
27.11.4 | Information classes | Y |
27.11.5 | Class `time_zone` | Y |
27.11.6 | Class template `zoned_traits` | Y |
27.11.7 | Class template `zoned_time` | Y |
27.11.8 | Class `leap_second` | Y |
27.11.9 | Class `time_zone_link` | Y |
27.12 | Formatting | Y |
27.13 | Parsing | Y |
27.14 | Header `<ctime>` synopsis | Y |
28 | Localization library
28.1 | General |  |
28.2 | Header `<locale>` synopsis | Y |
28.3 | Locales |  |
28.3.1 | Class `locale` | Y |
28.3.2 | `locale` globals | Y |
28.3.3 | Convenience interfaces |  |
28.3.3.1 | Character classification | Y |
28.3.3.2 | Character conversions | Y |
28.4 | Standard `locale` categories |  |
28.4.1 | General |  |
28.4.2 | The `ctype` category | Y |
28.4.3 | The numeric category | Y |
28.4.4 | The numeric punctuation facet | Y |
28.4.5 | The collate category | Y |
28.4.6 | The time category | Y |
28.4.7 | The monetary category | Y |
28.4.8 | The message retrieval category | Y |
28.5 | C library locales | Y |
29 | Input/output library
29.1 | General | Y |
29.2 | Iostreams requirements |  |
29.2.1 | Imbue limitations | Y |
29.2.2 | Positioning type limitations | Y |
29.2.3 | Thread safety | Partial |
29.3 | Forward declarations | Y |
29.4 | Standard iostream objects | Y |
29.5 | Iostreams base classes | Y |
29.6 | Stream buffers | Y |
29.7 | Formatting and manipulators | Y |
29.8 | String-based streams | Y |
29.9 | File-based streams | Y |
29.10 | Synchronized output streams |  |
29.10.1 | Header `<syncstream>` synopsis | Y |
29.10.2 | Class template `basic_syncbuf` | Y |
29.10.3 | Class template `basic_osyncstream` | Y |
29.11 | File systems |  |
29.11.1 | General |  |
29.11.2 | Conformance | Y |
29.11.3 | Requirements | Y |
29.11.4 | Header `<filesystem>` synopsis | Y |
29.11.5 | Error reporting | Y |
29.11.6 | Class `path` | Y |
29.11.7 | Class `filesystem_error` | Y |
29.11.8 | Enumerations |  |
29.11.8.1 | Enum `path::format` | Y |
29.11.8.2 | Enum class `file_type` | Y |
29.11.8.3 | Enum class `copy_options` | Y |
29.11.8.4 | Enum class `perms` | Y |
29.11.8.5 | Enum class `perm_options` | Y |
29.11.8.6 | Enum class `directory_options` | Y |
29.11.9 | Class `file_status` | Y |
29.11.10 | Class `directory_entry` | Y |
29.11.11 | Class `directory_iterator` | Y |
29.11.12 | Class `recursive_directory_iterator` | Y |
29.11.13 | Filesystem operation functions | Y |
29.12 | C library files |  |
29.12.1 | Header `<cstdio>` synopsis | Y |
29.12.2 | Header `<cinttypes>` synopsis | Y |
30 | Regular expressions library
30.1 | General | Y |
30.2 | Requirements | Y |
30.3 | Header `<regex>` synopsis | Y |
30.4 | Namespace `std::regex_constants` | Y |
30.5 | Class `regex_error` | Y |
30.6 | Class template `regex_traits` | Partial | `transform_primary` is not correctly implemented
30.7 | Class template `basic_regex` | Y |
30.8 | Class template `sub_match` | Y |
30.9 | Class template `match_results` | Y |
30.10 | Regular expression algorithms | Y |
30.11 | Regular expression iterators | Y |
30.12 | Modified ECMAScript regular expression grammar | Y |
31 | Atomics library
31.1 | General | Y |
31.2 | Header `<atomic>` synopsis | Y |
31.3 | Type aliases | Y |
31.4 | Order and consistency | Y |
31.5 | Lock-free property | Y |
31.6 | Waiting and notifying | Partial | Waiting and notifying is not supported for volatile objects.
31.7 | Class template `atomic_ref` |  |
31.7.1 | General | Y |
31.7.2 | Operations | Partial | volatile-qualified overloads for `wait`, `notify_one`, and `notify_all` are not provided.
31.7.3 | Specializations for integral types | Y |
31.7.4 | Specializations for floating-point types | Y |
31.7.5 | Partial specialization for pointers | Y |
31.8 | Class template `atomic` |  |
31.8.1 | General | Y |
31.8.2 | Operations on atomic types | Partial | Waiting and notifying is not supported for volatile objects.
31.8.3 | Specializations for integers | Y |
31.8.4 | Specializations for floating-point types | Y |
31.8.5 | Partial specialization for pointers | Y |
31.8.6 | Member operators common to integers and pointers to objects | Y |
31.8.7 | Partial specializations for smart pointers |  |
31.8.7.1 | General | Y |
31.8.7.2 | Partial specialization for `shared_ptr` | Y |
31.8.7.3 | Partial specialization for `weak_ptr` | Y |
31.9 | Non-member functions | Y |
31.10 | Flag type and operations | Y |
31.11 | Fences | Y |
32 | Threads library
32.1 | General | Y |
32.2 | Requirements | Y |
32.3 | Stop tokens |  |
32.3.1 | Introduction | Y |
32.3.2 | Header `<stop_token>` synopsis | Y |
32.3.3 | Class `stop_token` | Y |
32.3.4 | Class `stop_source` | Y |
32.3.5 | Class template `stop_callback` | Y |
32.4 | Threads |  |
32.4.1 | General |  |
32.4.2 | Header `<thread>` synopsis | Y |
32.4.3 | Class `thread` | Partial | `thread::id` comparisons not well-defined
32.4.4 | Class `jthread` | Y |
32.4.5 | Namespace `this_thread` | Y |
32.5 | Mutual exclusion |  |
32.5.1 | General |  |
32.5.2 | Header `<mutex>` synopsis |  |
32.5.3 | Header `<shared_mutex>` synopsis |  |
32.5.4 | Mutex requirements |  |
32.5.4.1 | In general |  |
32.5.4.2 | Mutex types | Y |
32.5.4.3 | Timed mutex types | Y |
32.5.4.4 | Shared mutex types | Y |
32.5.4.5 | Shared timed mutex types | Y |
32.5.5 | Locks | Y |
32.5.6 | Generic locking algorithms | Y |
32.5.7 | Call once |  |
32.5.7.1 | Struct `once_flag` | Y |
32.5.7.2 | Function `call_once` | Partial | Exception support is broken. See PR 66146.
32.6 | Condition variables | Y |
32.7 | Semaphore | Y |
32.7.1 | General |  |
32.7.2 | Header `<semaphore>` synopsis | Y |
32.7.3 | Class template `counting_semaphore` | Y |
32.8 | Coordination types |  |
32.8.1 | General |  |
32.8.2 | Latches |  |
32.8.2.1 | General |  |
32.8.2.2 | Header `<latch>` synopsis | Y |
32.8.2.3 | Class `latch` | Y |
32.8.3 | Barriers |  |
32.8.3.1 | General |  |
32.8.3.2 | Header `<barrier>` synopsis | Y |
32.8.3.3 | Class template `barrier` | Y |
32.9 | Futures | Y |
Appendix D | Compatibility features
D.10 | C headers |  |
D.10.1 | General | Y |
D.10.2 | Header `<complex.h>` synopsis | Y |
D.10.3 | Header `<iso646.h>` synopsis | Y |
D.10.4 | Header `<stdalign.h>` synopsis | Y |
D.10.5 | Header `<stdbool.h>` synopsis | Y |
D.10.6 | Header `<tgmath.h>` synopsis | Y |
D.10.7 | Other C headers | Y |
D.12 | Relational operators | Y |
D.13 | `char*` streams | Y |
D.13.1 | Header `<strstream>` synopsis | Y |
D.13.2 | Class `strstreambuf` | Y |
D.13.3 | Class `istrstream` | Y |
D.13.4 | Class `ostrstream` | Y |
D.13.5 | Class `strstream` | Y |
D.14 | Deprecated type traits | Y |
D.15 | Tuple | Y |
D.16 | Variant | Y |
D.17 | Deprecated `iterator` class template | Y |
D.18 | Deprecated `move_iterator` access | Y |
D.19 | Deprecated `shared_ptr` atomic access | Y |
D.20 | Deprecated `basic_string` capacity | Y |
D.21 | Deprecated standard code conversion facets |  |
D.21.1 | General | Y |
D.21.2 | Header `<codecvt>` synopsis | Y |
D.21.3 | Requirements | Y |
D.22 | Deprecated convenience conversion interfaces |  |
D.22.1 | General | Y |
D.22.2 | Class template `wstring_convert` | Y |
D.22.3 | Class template `wbuffer_convert` | Y |
D.23 | Deprecated locale category facets | Y |
D.24 | Deprecated filesystem path factory functions | Y |
D.25 | Deprecated atomic operations |  |
D.25.1 | General | Y |
D.25.2 | Volatile access | Y |
D.25.3 | Non-member functions | Y |
D.25.4 | Operations on atomic types | Y |
D.25.5 | Flag type and operations | Y |

#### Implementation Specific Behavior

For behaviour which is also specified by previous standards, see C++ 1998/2003 Implementation Specific Behavior, C++ 2011 Implementation Specific Behavior, and C++ 2017 Implementation Specific Behavior. This section only documents behaviour which is new in the 2020 standard.

16.4.2.4 [compliance] The implementation is freestanding if the `-ffreestanding` compiler flag is used, and hosted otherwise.

16.4.2.4 [compliance] The support for always lock-free integral atomic types and presence of `atomic_signed_lock_free` and `atomic_unsigned_lock_free` type aliases depends on the target.

27.5.11 [time.duration.io] The `"μs"` (`"\u00b5\u0073"`) is used for `std::micro` `Period::type` if the macro `_GLIBCXX_USE_ALT_MICROSECONDS_SUFFIX` is defined to a value other than zero before inclusion of the `chrono` header, `"us"` is used otherwise.

29.8.2.2 [stringbuf.cons] Sequence pointers are initialized to null pointers by the `basic_stringbuf(ios_base::openmode)` constructor.

31.7.1 [atomics.ref.generic.general], 31.7.3 [atomics.ref.int], 31.7.4 [atomics.ref.float], 31.7.5 [atomics.ref.pointer] The values of `is_always_lock_free` members depend on the target and cannot be listed here.

31.7.1 [atomics.ref.generic.general] If `sizeof(T)` is equal to either `1`, `2`, `4`, `8`, or `16`, then the value of `required_alignment` member is equal to the maximum of `alignof(T)` and `sizeof(T)`. Otherwise `required_alignment` value is `alignof(T)`.

31.7.3 [atomics.ref.int] The value of `required_alignment` member is equal to the maximum of `alignof(value_type)` and `sizeof(value_type)`.

31.7.4 [atomics.ref.float], 31.7.5 [atomics.ref.pointer] The value of `required_alignment` member is equal to `alignof(value_type)`.

32.7.3 [thread.sema.cnt] The value of default argument for the `least_max_value` parameter depends on the target operating system and platform, however the value of `counting_semaphore<>::max()` is greater than or equal to `numeric_limits<int>::max()`.

### C++ 2023

In this implementation the `-std=gnu++23` or `-std=c++23` flag must be used to enable language and library features. See dialect options. The pre-defined symbol `__cplusplus` is used to check for the presence of the required flag.

This section describes the C++23 and library TS support in mainline GCC, not in any particular release.

The following table lists new library features that have been accepted into the C++23 working draft. The "Proposal" column provides a link to the ISO C++ committee proposal that describes the feature, while the "Status" column indicates the first version of GCC that contains an implementation of this feature (if it has been implemented). A dash (—) in the status column indicates that the changes in the proposal either do not affect the code in libstdc++, or the changes are not required for conformance. The "SD-6 Feature Test / Notes" column shows the corresponding macro or header from SD-6: Feature-testing recommendations for C++ (where applicable) or any notes about the implementation.

Table 1.11. C++ 2023 Library Features

Library Feature | Proposal | Status | SD-6 Feature Test / Notes
--- | --- | --- | ---
Ranges and Views
Range constructor for std::string_view | P1989R2 | 11.1 |
`join_view` should join all views of ranges | P2328R1 | 11.2 |
Clarifying range adaptor objects | P2281R1 | 11.1 |
Views should not be required to be default constructible | P2325R3 | 11.3 | `__cpp_lib_ranges >= 202106L`
Conditionally borrowed ranges | P2017R1 | 11.1 |
Require `span` & `basic_string_view` to be Trivially Copyable | P2251R1 | Yes |
Repairing input range adaptors and counted_iterator | P2259R1 | 12.1 |
Superior String Splitting | P2210R2 | 12.1 |
What is a `view`? | P2415R2 | 12.1 | `__cpp_lib_ranges >= 202110L`
Fix istream_view | P2432R1 | 12.1 |
`starts_with` and `ends_with` | P1659R3 | 16.1 | `__cpp_lib_ranges_starts_ends_with >= 202106L`
`zip` | P2321R2 | 13.1 | `__cpp_lib_ranges_zip >= 202110L`
`views::repeat` | P2474R2 | 13.1 | `__cpp_lib_ranges_repeat >= 202207L`
`views::enumerate` | P2164R9 | 13.1 | `__cpp_lib_ranges_enumerate >= 202302L`
`views::join_with` | P2441R2 | 13.1 | `__cpp_lib_ranges_join_with >= 202202L`
Windowing range adaptors: `views::chunk` and `views::slide` | P2442R1 | 13.1 | `__cpp_lib_ranges_slide >= 202202L`
`views::chunk_by` | P2443R1 | 13.1 | `__cpp_lib_ranges_chunk_by >= 202202L`
`views::stride` | P1899R3 | 13.1 | `__cpp_lib_ranges_stride >= 202207L`
`views::cartesian_product` | P2374R4 | 13.1 | `__cpp_lib_ranges_cartesian_product >= 202207L`
Empty Product for certain Views | P2540R1 | 13.1 | `__cpp_lib_ranges_cartesian_product >= 202207L`
`views::as_rvalue` | P2446R2 | 13.1 | `__cpp_lib_ranges_as_rvalue >= 202207L`
`cbegin` should always return a constant iterator | P2278R4 | 13.1 | `__cpp_lib_ranges_as_const >= 202207L`
`ranges::to` | P1206R7 |
14.1 (`ranges::to` function)
15.1 (new members in containers)
| `__cpp_lib_ranges_to_container >= 202202L`, `__cpp_lib_containers_ranges >= 202202L`
Ranges iterators as inputs to non-Ranges algorithms | P2408R5 | 16.1 | `__cpp_lib_algorithm_iterator_requirements >= 202207L`
Pipe support for user-defined range adaptors | P2387R3 | 13.1 | `__cpp_lib_bind_pack >= 202202L`, `__cpp_lib_ranges >= 202202L`
`ranges::iota`, `ranges::shift_left`, and `ranges::shift_right` | P2440R1 |
13.1 (`ranges::iota`)
16.1 (shift algos)
| `__cpp_lib_ranges_iota >= 202202L`, `__cpp_lib_shift >= 202202L`
`ranges::find_last` | P1223R5 | 13.1 | `__cpp_lib_ranges_find_last >= 202207L`
`ranges::contains` | P2302R4 | 13.1 | `__cpp_lib_ranges_contains >= 202207L`
Making multi-param constructors of views explicit | P2711R1 | 16.1 |
`ranges::fold` | P2322R6 | 13.1 | `__cpp_lib_ranges_fold >= 202207L`
Relaxing Ranges Just A Smidge | P2609R3 | 14.3 | `__cpp_lib_ranges >= 202302L`
Compile-time programming
A proposal for a type trait to detect scoped enumerations | P1048R1 | 11.1 | `__cpp_lib_is_scoped_enum >= 202011L`
std::to_underlying for enumerations | P1682R3 | 11.1 | `__cpp_lib_to_underlying >= 202102L`
Missing constexpr in std::optional and std::variant | P2231R1 |
11.3 (`optional`)
12.1 (`variant`)
`__cpp_lib_constexpr_optional >= 202106L`
`__cpp_lib_variant >= 202106L`
Making `std::unique_ptr` constexpr | P2273R3 | 12.1 | `__cpp_lib_constexpr_memory >= 202202L`
Making `std::type_info::operator==` constexpr | P1328R1 | 12.1 | `__cpp_lib_constexpr_typeinfo >= 202106L`
constexpr for `<cmath>` and `<cstdlib>` | P0533R9 |  | `__cpp_lib_constexpr_cmath >= 202202L`
Deprecate std::aligned_storage and std::aligned_union | P1413R3 | 13.1 |
A type trait to detect reference binding to temporary | P2255R2 |
13.1 (missing changes to `std::tuple`)
14.1 (complete)
| `__cpp_lib_reference_from_temporary >= 202202L`
Move-only types for equality_comparable_with, totally_ordered_with, and three_way_comparable_with | P2404R3 | 16.1 | `__cpp_lib_concepts >= 202207L`
A trait for implicit lifetime types | P2674R1 | 16.1 | `__cpp_lib_is_implicit_lifetime >= 202302L`
`common_reference_t` of `reference_wrapper` Should Be a Reference Type | P2655R3 | 15.3 | `__cpp_lib_common_reference >= 202302L`
Deprecate `numeric_limits::has_denorm` | P2614R2 |  |
Containers
Iterator pair constructors for stack and queue | P1425R4 | 12.1 | `__cpp_lib_adaptor_iterator_pair_constructor >= 202106L`
Stop overconstraining allocators in container deduction guides | P1518R2 | 12.1 |
Heterogeneous erasure overloads for associative containers | P2077R3 | 16.1 | `__cpp_lib_associative_heterogeneous_erasure >= 202110L`
`<flat_map>` | P0429R9 | 15.1 | `__cpp_lib_flat_map >= 202207L`
`<flat_set>` | P1222R4 | 15.1 | `__cpp_lib_flat_set >= 202207L`
`mdspan` | P0009R18 | 16.1 | `__cpp_lib_mdspan >= 202207L`
`index_type` & `size_type` in `mdspan` | P2599R2 | 16.1 | `__cpp_lib_mdspan >= 202207L`
`mdspan`: rename `pointer` and `contiguous` | P2604R0 | 16.1 | `__cpp_lib_mdspan >= 202207L`
Add the missing `empty` to `mdspan` | P2613R1 | 16.1 | `__cpp_lib_mdspan >= 202207L`
`layout_stride` static extents default constructor fix | P2763R1 | 16.1 |
Strings and text
string contains function | P1679R3 | 11.1 | `__cpp_lib_string_contains >= 202011L`
Prohibit std::basic_string and std::basic_string_view construction from nullptr | P2166R1 | 12.1 |
basic_string::resize_and_overwrite | P1072R10 | 12.1 | `__cpp_lib_resize_and_overwrite >= 202110L`
A strstream replacement using span<charT> as buffer | P0448R4 | 12.1 | `__cpp_lib_spanstream >= 202106L`
`std::string::substr() &&` | P2438R2 |  |
std::format improvements | P2216R3 | 13.1 | `__cpp_lib_format >= 202106L`
Add support for `std::generator`-like types to `std::format` | P2418R2 | 13.1 | `__cpp_lib_format >= 202110L`
Expose `std::basic-format-string<charT, Args...>` | P2508R1 | 13.1 (feature test macro not updated until 15.1) | `__cpp_lib_format >= 202207L`
Clarify handling of encodings in localized formatting of chrono types | P2419R2 | 15.1 | `__cpp_lib_format >= 202207L`
Formatting pointers | P2510R3 | 13.2 (feature test macro not updated until 15.1) | `__cpp_lib_format >= 202207L`
Formatting Ranges | P2286R8 |
15.1 (changes to adaptors missing)
15.2 (complete)
| `__cpp_lib_format_ranges >= 202207L`
Improve default container formatting | P2585R1 | 15.1 (feature test macro not defined until 15.2) | `__cpp_lib_format_ranges >= 202207L`
Formatted output | P2093R14 | 14.1 | `__cpp_lib_print >= 202207L`
Should the output of std::print to a terminal be synchronized with the underlying stream? | P2539R3 | 14.1 |
Formatting `thread::id` and `stacktrace` | P2693R1 | 14.1 | `__cpp_lib_formatters >= 202302L`
Add Constexpr Modifiers to Functions `to_chars` and `from_chars` for Integral Types in `<charconv>` Header | P2291R3 | 13.1 | `__cpp_lib_constexpr_charconv >= 202207L`
Miscellaneous
Inheriting from `std::variant` | P2162R2 | 11.3 | `__cpp_lib_variant >= 202102L`
Printing `volatile` Pointers | P1147R1 | 11.3 |
A Proposal to add stacktrace library | P0881R7 | 12.1 | `__cpp_lib_stacktrace >= 202011L`
Add a pmr alias for std::stacktrace | P2301R1 | 12.1 |
`std::expected` | P0323R12 | 12.1 | `__cpp_lib_expected >= 202202L`
Monadic operations for std::expected | P2505R5 | 13.1 | `__cpp_lib_expected >= 202211L`
Monadic operations for std::optional | P0798R8 | 12.1 | `__cpp_lib_optional >= 202110L`
Compatibility between `tuple`, `pair` and tuple-like objects | P2165R4 | 14.1 | `__cpp_lib_tuple_like >= 202207L`
Default Arguments for `pair`'s Forwarding Constructor | P1951R1 | 14.1 |
`move_only_function` | P0288R9 | 12.1 | `__cpp_lib_move_only_function >= 202110L`
`invoke_r` | P2136R3 | 12.1 | `__cpp_lib_invoke_r >= 202106L`
Byteswapping for fun&&nuf | P1272R4 | 12.1 | `__cpp_lib_byteswap >= 202110L`
Function to mark unreachable code | P0627R6 | 12.1 | `__cpp_lib_unreachable >= 202202L`
Add a conditional noexcept specification to std::exchange | P2401R0 | 12.1 |
A more constexpr bitset | P2417R2 | 13.1 | `__cpp_lib_constexpr_bitset >= 202207L`
Extended floating-point types and standard names | P1467R9 | 13.1 |
Support C atomics in C++ | P0943R6 | 12.1 | `__cpp_lib_stdatomic_h >= 202011L`
Clarifying the status of the "C headers" | P2340R1 | Yes |
Relax Requirements for time_point::clock | P2212R2 | Yes |
Removing Garbage Collection Support | P2186R2 | 12.1 |
Easy [utilities], [ranges], and [iterators] | P1642R11 | 13.1 |
Providing size feedback in the Allocator interface | P0401R6 | 16.1 | `__cpp_lib_allocate_at_least >= 202306L`
Disallow User Specialization of `allocator_traits` | P2652R2 |  |
Explicit lifetime management | P2590R2 | 16.1 | `__cpp_lib_start_lifetime_as >= 202207L`
Fixing `std::start_lifetime_as` and `std::start_lifetime_as_array` | P2679R2 | 16.1 |
out_ptr - a scalable output pointer abstraction | P1132R8 | 14.1 | `__cpp_lib_out_ptr >= 202106L`
`barrier`'s phase completion guarantees | P2588R3 |  | `__cpp_lib_barrier >= 202302L`
Standard Library Modules `std` and `std.compat` | P2465R3 | 15.1 | `__cpp_lib_modules >= 202207L`

### C++ TR1

This table is based on the table of contents of ISO/IEC DTR 19768, Doc No: N1836=05-0096, Date: 2005-06-24, "Draft Technical Report on C++ Library Extensions".

In this implementation the header names are prefixed by `tr1/`, for instance `<tr1/functional>`, `<tr1/memory>`, and so on.

This page describes the TR1 support in mainline GCC, not in any particular release.

Table 1.12. C++ TR1 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
2 | General Utilities
2.1 | Reference wrappers |  |
2.1.1 | Additions to header `<functional>` synopsis | Y |
2.1.2 | Class template `reference_wrapper` |  |
2.1.2.1 | `reference_wrapper` construct/copy/destroy | Y |
2.1.2.2 | `reference_wrapper` assignment | Y |
2.1.2.3 | `reference_wrapper` access | Y |
2.1.2.4 | `reference_wrapper` invocation | Y |
2.1.2.5 | `reference_wrapper` helper functions | Y |
2.2 | Smart pointers |  |
2.2.1 | Additions to header `<memory>` synopsis | Y |
2.2.2 | Class `bad_weak_ptr` | Y |
2.2.3 | Class template `shared_ptr` |  | Uses code from boost::shared_ptr.
2.2.3.1 | `shared_ptr` constructors | Y |
2.2.3.2 | `shared_ptr` destructor | Y |
2.2.3.3 | `shared_ptr` assignment | Y |
2.2.3.4 | `shared_ptr` modifiers | Y |
2.2.3.5 | `shared_ptr` observers | Y |
2.2.3.6 | `shared_ptr` comparison | Y |
2.2.3.7 | `shared_ptr` I/O | Y |
2.2.3.8 | `shared_ptr` specialized algorithms | Y |
2.2.3.9 | `shared_ptr` casts | Y |
2.2.3.10 | `get_deleter` | Y |
2.2.4 | Class template `weak_ptr` |  |
2.2.4.1 | `weak_ptr` constructors | Y |
2.2.4.2 | `weak_ptr` destructor | Y |
2.2.4.3 | `weak_ptr` assignment | Y |
2.2.4.4 | `weak_ptr` modifiers | Y |
2.2.4.5 | `weak_ptr` observers | Y |
2.2.4.6 | `weak_ptr` comparison | Y |
2.2.4.7 | `weak_ptr` specialized algorithms | Y |
2.2.5 | Class template `enable_shared_from_this` | Y |
3 | Function Objects
3.1 | Definitions | Y |
3.2 | Additions to `<functional> synopsis` | Y |
3.3 | Requirements | Y |
3.4 | Function return types | Y |
3.5 | Function template `mem_fn` | Y |
3.6 | Function object binders |  |
3.6.1 | Class template `is_bind_expression` | Y |
3.6.2 | Class template `is_placeholder` | Y |
3.6.3 | Function template `bind` | Y |
3.6.4 | Placeholders | Y |
3.7 | Polymorphic function wrappers |  |
3.7.1 | Class `bad_function_call` | Y |
3.7.1.1 | `bad_function_call` constructor | Y |
3.7.2 | Class template `function` |  |
3.7.2.1 | `function` construct/copy/destroy | Y |
3.7.2.2 | `function` modifiers | Y |
3.7.2.3 | `function` capacity | Y |
3.7.2.4 | `function` invocation | Y |
3.7.2.5 | `function` target access | Y |
3.7.2.6 | undefined operators | Y |
3.7.2.7 | null pointer comparison operators | Y |
3.7.2.8 | specialized algorithms | Y |
4 | Metaprogramming and type traits
4.1 | Requirements | Y |
4.2 | Header `<type_traits>` synopsis | Y |
4.3 | Helper classes | Y |
4.4 | General Requirements | Y |
4.5 | Unary Type Traits |  |
4.5.1 | Primary Type Categories | Y |
4.5.2 | Composite type traits | Y |
4.5.3 | Type properties | Y |
4.6 | Relationships between types | Y |
4.7 | Transformations between types |  |
4.7.1 | Const-volatile modifications | Y |
4.7.2 | Reference modifications | Y |
4.7.3 | Array modifications | Y |
4.7.4 | Pointer modifications | Y |
4.8 | Other transformations | Y |
4.9 | Implementation requirements | Y |
5 | Numerical Facilities
5.1 | Random number generation |  |
5.1.1 | Requirements | Y |
5.1.2 | Header `<random>` synopsis | Y |
5.1.3 | Class template `variate_generator` | Y |
5.1.4 | Random number engine class templates | Y |
5.1.4.1 | Class template `linear_congruential` | Y |
5.1.4.2 | Class template `mersenne_twister` | Y |
5.1.4.3 | Class template `subtract_with_carry` | Y |
5.1.4.4 | Class template `subtract_with_carry_01` | Y |
5.1.4.5 | Class template `discard_block` | Y |
5.1.4.6 | Class template `xor_combine` | Y | operator()() per N2079
5.1.5 | Engines with predefined parameters | Y |
5.1.6 | Class `random_device` | Y |
5.1.7 | Random distribution class templates | Y |
5.1.7.1 | Class template `uniform_int` | Y |
5.1.7.2 | Class `bernoulli_distribution` | Y |
5.1.7.3 | Class template `geometric_distribution` | Y |
5.1.7.4 | Class template `poisson_distribution` | Y |
5.1.7.5 | Class template `binomial_distribution` | Y |
5.1.7.6 | Class template `uniform_real` | Y |
5.1.7.7 | Class template `exponential_distribution` | Y |
5.1.7.8 | Class template `normal_distribution` | Y |
5.1.7.9 | Class template `gamma_distribution` | Y |
5.2 | Mathematical special functions | Y |
5.2.1 | Additions to header `<cmath>` synopsis | Y |
5.2.1.1 | associated Laguerre polynomials | Y |
5.2.1.2 | associated Legendre functions | Y |
5.2.1.3 | beta function | Y |
5.2.1.4 | (complete) elliptic integral of the first kind | Y |
5.2.1.5 | (complete) elliptic integral of the second kind | Y |
5.2.1.6 | (complete) elliptic integral of the third kind | Y |
5.2.1.7 | confluent hypergeometric functions | Y |
5.2.1.8 | regular modified cylindrical Bessel functions | Y |
5.2.1.9 | cylindrical Bessel functions (of the first kind) | Y |
5.2.1.10 | irregular modified cylindrical Bessel functions | Y |
5.2.1.11 | cylindrical Neumann functions | Y |
5.2.1.12 | (incomplete) elliptic integral of the first kind | Y |
5.2.1.13 | (incomplete) elliptic integral of the second kind | Y |
5.2.1.14 | (incomplete) elliptic integral of the third kind | Y |
5.2.1.15 | exponential integral | Y |
5.2.1.16 | Hermite polynomials | Y |
5.2.1.17 | hypergeometric functions | Y |
5.2.1.18 | Laguerre polynomials | Y |
5.2.1.19 | Legendre polynomials | Y |
5.2.1.20 | Riemann zeta function | Y |
5.2.1.21 | spherical Bessel functions (of the first kind) | Y |
5.2.1.22 | spherical associated Legendre functions | Y |
5.2.1.23 | spherical Neumann functions | Y |
5.2.2 | Additions to header `<math.h>` synopsis | Y |
6 | Containers
6.1 | Tuple types | Y |
6.1.1 | Header `<tuple>` synopsis | Y |
6.1.2 | Additions to header `<utility>` synopsis | Y |
6.1.3 | Class template `tuple` | Y |
6.1.3.1 | Construction | Y |
6.1.3.2 | Tuple creation functions | Y |
6.1.3.3 | Tuple helper classes | Y |
6.1.3.4 | Element access | Y |
6.1.3.5 | Relational operators | Y |
6.1.4 | Pairs | Y |
6.2 | Fixed size array | Y |
6.2.1 | Header `<array>` synopsis | Y |
6.2.2 | Class template `array` | Y |
6.2.2.1 | `array` constructors, copy, and assignment | Y |
6.2.2.2 | `array` specialized algorithms | Y |
6.2.2.3 | `array` size | Y |
6.2.2.4 | Zero sized `array`s | Y |
6.2.2.5 | Tuple interface to class template `array` | Y |
6.3 | Unordered associative containers | Y |
6.3.1 | Unordered associative container requirements | Y |
6.3.1.1 | Exception safety guarantees | Y |
6.3.2 | Additions to header `<functional>` synopsis | Y |
6.3.3 | Class template `hash` | Y |
6.3.4 | Unordered associative container classes | Y |
6.3.4.1 | Header `<unordered_set>` synopsis | Y |
6.3.4.2 | Header `<unordered_map>` synopsis | Y |
6.3.4.3 | Class template `unordered_set` | Y |
6.3.4.3.1 | `unordered_set` constructors | Y |
6.3.4.3.2 | `unordered_set` swap | Y |
6.3.4.4 | Class template `unordered_map` | Y |
6.3.4.4.1 | `unordered_map` constructors | Y |
6.3.4.4.2 | `unordered_map` element access | Y |
6.3.4.4.3 | `unordered_map` swap | Y |
6.3.4.5 | Class template `unordered_multiset` | Y |
6.3.4.5.1 | `unordered_multiset` constructors | Y |
6.3.4.5.2 | `unordered_multiset` swap | Y |
6.3.4.6 | Class template `unordered_multimap` | Y |
6.3.4.6.1 | `unordered_multimap` constructors | Y |
6.3.4.6.2 | `unordered_multimap` swap | Y |
7 | Regular Expressions
7.1 | Definitions | N |
7.2 | Requirements | N |
7.3 | Regular expressions summary | N |
7.4 | Header `<regex>` synopsis | N |
7.5 | Namespace `tr1::regex_constants` | N |
7.5.1 | Bitmask Type `syntax_option_type` | N |
7.5.2 | Bitmask Type `regex_constants::match_flag_type` | N |
7.5.3 | Implementation defined `error_type` | N |
7.6 | Class `regex_error` | N |
7.7 | Class template `regex_traits` | N |
7.8 | Class template `basic_regex` | N |
7.8.1 | `basic_regex` constants | N |
7.8.2 | `basic_regex` constructors | N |
7.8.3 | `basic_regex` assign | N |
7.8.4 | `basic_regex` constant operations | N |
7.8.5 | `basic_regex` locale | N |
7.8.6 | `basic_regex` swap | N |
7.8.7 | `basic_regex` non-member functions | N |
7.8.7.1 | `basic_regex` non-member swap | N |
7.9 | Class template `sub_match` | N |
7.9.1 | `sub_match` members | N |
7.9.2 | `sub_match` non-member operators | N |
7.10 | Class template `match_results` | N |
7.10.1 | `match_results` constructors | N |
7.10.2 | `match_results` size | N |
7.10.3 | `match_results` element access | N |
7.10.4 | `match_results` formatting | N |
7.10.5 | `match_results` allocator | N |
7.10.6 | `match_results` swap | N |
7.11 | Regular expression algorithms | N |
7.11.1 | exceptions | N |
7.11.2 | `regex_match` | N |
7.11.3 | `regex_search` | N |
7.11.4 | `regex_replace` | N |
7.12 | Regular expression Iterators | N |
7.12.1 | Class template `regex_iterator` | N |
7.12.1.1 | `regex_iterator` constructors | N |
7.12.1.2 | `regex_iterator` comparisons | N |
7.12.1.3 | `regex_iterator` dereference | N |
7.12.1.4 | `regex_iterator` increment | N |
7.12.2 | Class template `regex_token_iterator` | N |
7.12.2.1 | `regex_token_iterator` constructors | N |
7.12.2.2 | `regex_token_iterator` comparisons | N |
7.12.2.3 | `regex_token_iterator` dereference | N |
7.12.2.4 | `regex_token_iterator` increment | N |
7.13 | Modified ECMAScript regular expression grammar | N |
8 | C Compatibility
8.1 | Additions to header `<complex>` | Y |
8.1.1 | Synopsis | Y |
8.1.2 | Function `acos` | Y |
8.1.3 | Function `asin` | Y |
8.1.4 | Function `atan` | Y |
8.1.5 | Function `acosh` | Y |
8.1.6 | Function `asinh` | Y |
8.1.7 | Function `atanh` | Y |
8.1.8 | Function `fabs` | Y |
8.1.9 | Additional Overloads | Y |
8.2 | Header `<ccomplex>` | N | DR 551
8.3 | Header `<complex.h>` | N | DR 551
8.4 | Additions to header `<cctype>` | Y |
8.4.1 | Synopsis | Y |
8.4.2 | Function `isblank` | Y |
8.5 | Additions to header `<ctype.h>` | Y |
8.6 | Header `<cfenv>` | Y |
8.6.1 | Synopsis | Y |
8.6.2 | Definitions | Y |
8.7 | Header `<fenv.h>` | Y |
8.8 | Additions to header `<cfloat>` | Y |
8.9 | Additions to header `<float.h>` | Y |
8.10 | Additions to header `<ios>` | N |
8.10.1 | Synopsis | N |
8.10.2 | Function `hexfloat` | N |
8.11 | Header `<cinttypes>` | Y |
8.11.1 | Synopsis | Y | DR 557
8.11.2 | Definitions | Y |
8.12 | Header `<inttypes.h>` | Y |
8.13 | Additions to header `<climits>` | Y |
8.14 | Additions to header `<limits.h>` | Y |
8.15 | Additions to header `<locale>` | N |
8.16 | Additions to header `<cmath>` | Y |
8.16.1 | Synopsis | Y |
8.16.2 | Definitions | Y |
8.16.3 | Function template definitions | Y |
8.16.4 | Additional overloads | Y | DR 568; DR 550
8.17 | Additions to header `<math.h>` | Y |
8.18 | Additions to header `<cstdarg>` | Y |
8.19 | Additions to header `<stdarg.h>` | Y |
8.20 | The header `<cstdbool>` | Y |
8.21 | The header `<stdbool.h>` | Y |
8.22 | The header `<cstdint>` | Y |
8.22.1 | Synopsis | Y |
8.22.2 | Definitions | Y |
8.23 | The header `<stdint.h>` | Y |
8.24 | Additions to header `<cstdio>` | Y |
8.24.1 | Synopsis | Y |
8.24.2 | Definitions | Y |
8.24.3 | Additional format specifiers | Y | C library dependency
8.24.4 | Additions to header `<stdio.h>` | Y |
8.25 | Additions to header `<cstdlib>` | Y |
8.25.1 | Synopsis | Y |
8.25.2 | Definitions | Y |
8.25.3 | Function `abs` | Y |
8.25.4 | Function `div` | Y |
8.26 | Additions to header `<stdlib.h>` | Y |
8.27 | Header `<ctgmath>` | Y | DR 551
8.28 | Header `<tgmath.h>` | Y | DR 551
8.29 | Additions to header `<ctime>` | Y | C library dependency
8.30 | Additions to header `<cwchar>` | Y |
8.30.1 | Synopsis | Y |
8.30.2 | Definitions | Y |
8.30.3 | Additional wide format specifiers | Y | C library dependency
8.31 | Additions to header `<wchar.h>` | Y |
8.32 | Additions to header `<cwctype>` | Y |
8.32.1 | Synopsis | Y |
8.32.2 | Function `iswblank` | Y |
8.33 | Additions to header `<wctype.h>` | Y |

#### Implementation Specific Behavior

For behaviour which is specified by the 1998 and 2003 standards, see C++ 1998/2003 Implementation Specific Behavior. This section documents behaviour which is required by TR1.

3.6.4 [tr.func.bind.place]/1 There are 29 placeholders defined and the placeholder types are `Assignable`.

### C++ TR 24733

This table is based on the table of contents of ISO/IEC TR 24733:2011, "Extensions for the programming language C++ to support decimal floating-point arithmetic".

This page describes the TR 24733 support in mainline GCC, not in any particular release.

Table 1.13. C++ TR 24733 Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
0 | Introduction
1 | Normative references
2 | Conventions
3 | Decimal floating-point types
3.1 | Characteristics of decimal floating-point types |  |
3.2 | Decimal Types |  |
3.2.1 | Class `decimal` synopsis | Partial | Missing declarations for formatted input/output; non-conforming extension for functions converting to integral type
3.2.2 | Class `decimal32` | Partial | Missing 3.2.2.5 conversion to integral type; conforming extension for conversion from scalar decimal floating-point
3.2.3 | Class `decimal64` | Partial | Missing 3.2.3.5 conversion to integral type; conforming extension for conversion from scalar decimal floating-point
3.2.4 | Class `decimal128` | Partial | Missing 3.2.4.5 conversion to integral type; conforming extension for conversion from scalar decimal floating-point
3.2.5 | Initialization from coefficient and exponent | Y |
3.2.6 | Conversion to generic floating-point type | Y |
3.2.7 | Unary arithmetic operators | Y |
3.2.8 | Binary arithmetic operators | Y |
3.2.9 | Comparison operators | Y |
3.2.10 | Formatted input | N |
3.2.11 | Formatted output | N |
3.3 | Additions to header `limits` | N |
3.4 | Headers `cfloat` and `float.h` |  |
3.4.2 | Additions to header `cfloat` synopsis | Y |
3.4.3 | Additions to header `float.h` synopsis | N |
3.4.4 | Maximum finite value | Y |
3.4.5 | Epsilon | Y |
3.4.6 | Minimum positive normal value | Y |
3.4.7 | Minimum positive subnormal value | Y |
3.4.8 | Evaluation format | Y |
3.5 | Additions to `cfenv` and `fenv.h` | Outside the scope of GCC |
3.6 | Additions to `cmath` and `math.h` | Outside the scope of GCC |
3.7 | Additions to `cstdio` and `stdio.h` | Outside the scope of GCC |
3.8 | Additions to `cstdlib` and `stdlib.h` | Outside the scope of GCC |
3.9 | Additions to `cwchar` and `wchar.h` | Outside the scope of GCC |
3.10 | Facets | N |
3.11 | Type traits | N |
3.12 | Hash functions | N |
4 | Notes on C compatibility

### C++ IS 29124

This table is based on the table of contents of ISO/IEC FDIS 29124, Doc No: N3060, Date: 2010-03-06, "Extensions to the C++ Library to support mathematical special functions".

Complete support for IS 29124 is in GCC 6.1 and later releases, when using at least C++11 (for older releases or C++98/C++03 use TR1 instead). For C++11 and C++14 the additions to the library are not declared by their respective headers unless `__STDCPP_WANT_MATH_SPEC_FUNCS__` is defined as a macro that expands to a non-zero integer constant. For C++17 the special functions are always declared (since GCC 7.1).

When the special functions are declared the macro `__STDCPP_MATH_SPEC_FUNCS__` is defined to `201003L`.

In addition to the special functions defined in IS 29124, for non-strict modes (i.e. `-std=gnu++NN` modes) the hypergeometric functions and confluent hypergeometric functions from TR1 are also provided, defined in namespace `__gnu_cxx`.

Table 1.14. C++ Special Functions Implementation Status

Section | Description | Status | Comments
--- | --- | --- | ---
7 | Macro names | Partial | No diagnostic for inconsistent definitions of `__STDCPP_WANT_MATH_SPEC_FUNCS__`
8 | Mathematical special functions | Y |
8.1 | Additions to header `<cmath>` synopsis | Y |
8.1.1 | associated Laguerre polynomials | Y |
8.1.2 | associated Legendre functions | Y |
8.1.3 | beta function | Y |
8.1.4 | (complete) elliptic integral of the first kind | Y |
8.1.5 | (complete) elliptic integral of the second kind | Y |
8.1.6 | (complete) elliptic integral of the third kind | Y |
8.1.7 | regular modified cylindrical Bessel functions | Y |
8.1.8 | cylindrical Bessel functions (of the first kind) | Y |
8.1.9 | irregular modified cylindrical Bessel functions | Y |
8.1.10 | cylindrical Neumann functions | Y |
8.1.11 | (incomplete) elliptic integral of the first kind | Y |
8.1.12 | (incomplete) elliptic integral of the second kind | Y |
8.1.13 | (incomplete) elliptic integral of the third kind | Y |
8.1.14 | exponential integral | Y |
8.1.15 | Hermite polynomials | Y |
8.1.16 | Laguerre polynomials | Y |
8.1.17 | Legendre polynomials | Y |
8.1.18 | Riemann zeta function | Y |
8.1.19 | spherical Bessel functions (of the first kind) | Y |
8.1.20 | spherical associated Legendre functions | Y |
8.1.21 | spherical Neumann functions | Y |
8.2 | Additions to header `<math.h>` | Y |
8.3 | The header `<ctgmath>` | Partial | Conflicts with C++ 2011 requirements.
8.4 | The header `<tgmath.h>` | N | Conflicts with C++ 2011 requirements.

#### Implementation Specific Behavior

For behaviour which is specified by the 2011 standard, see C++ 2011 Implementation Specific Behavior. This section documents behaviour which is required by IS 29124.

7.2 [macro.user]/3 /4 The functions declared in Clause 8 are only declared when `__STDCPP_WANT_MATH_SPEC_FUNCS__ == 1` (or in C++17 mode, for GCC 7.1 and later).

8.1.1 [sf.cmath.Lnm]/1 The effect of calling these functions with `n >= 128` or `m >= 128` should be described here.

8.1.2 [sf.cmath.Plm]/3 The effect of calling these functions with `l >= 128` should be described here.

8.1.3 [sf.cmath.I]/3 The effect of calling these functions with `nu >= 128` should be described here.

8.1.8 [sf.cmath.J]/3 The effect of calling these functions with `nu >= 128` should be described here.

8.1.9 [sf.cmath.K]/3 The effect of calling these functions with `nu >= 128` should be described here.

8.1.10 [sf.cmath.N]/3 The effect of calling these functions with `nu >= 128` should be described here.

8.1.15 [sf.cmath.Hn]/3 The effect of calling these functions with `n >= 128` should be described here.

8.1.16 [sf.cmath.Ln]/3 The effect of calling these functions with `n >= 128` should be described here.

8.1.17 [sf.cmath.Pl]/3 The effect of calling these functions with `l >= 128` should be described here.

8.1.19 [sf.cmath.j]/3 The effect of calling these functions with `n >= 128` should be described here.

8.1.20 [sf.cmath.Ylm]/3 The effect of calling these functions with `l >= 128` should be described here.

8.1.21 [sf.cmath.n]/3 The effect of calling these functions with `n >= 128` should be described here.

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