Chapter 1. Status

Chapter 1. Status
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Implementation Status

C++ 1998/2003

Implementation 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 @@ -1083,7 +1083,7 @@ since C++14 and the implementation is complete.

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

C++ 202a

C++ 2020

In this implementation the -std=gnu++2a or -std=c++2a flag must be used to enable language and library @@ -1096,483 +1096,451 @@ 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 have been accepted into -the C++2a working draft. The "Proposal" column provides a link to the +the C++20 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). -The "SD-6 Feature Test" column shows the corresponding macro or header from +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++. -

Table 1.8. C++ 2020 Implementation Status

Library Feature Proposal Status SD-6 Feature Test

Endian just Endian - - P0463R1 - - 8.1

Extending make_shared to Support Arrays - - P0674R1 - -

Floating Point Atomic - - P0020R6 - - 10.1

C++ Synchronized Buffered Ostream - - P0053R7 - -

Add constexpr modifiers to functions in <algorithm> and <utility> Headers

+Feature-testing recommendations for C++ (where applicable) +or any notes about the implementation. +

Table 1.8. 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 std::complex + 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

Make std::memory_order a scoped enumeration + P0415R1 + 9.1 __cpp_lib_constexpr_complex >= 201711L (since 9.4, see Note 1)

P0595R2 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 + __cpp_lib_constexpr_string >= 201907L

Making std::vector constexpr + + P1004R2 + __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 + Partial

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 +

__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 + __cpp_lib_syncbuf >= 201711L

Manipulators for C++ Synchronized Buffered Ostream + + P0753R2 + __cpp_lib_syncbuf >= 201803L

Make std::memory_order a scoped enumeration - P0439R0 - - 9.1

String Prefix and Suffix Checking + P0439R0 + 9.1

The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange + + P0528R3 +

Atomic shared_ptr + + P0718R2 + __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 +

__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

+ Time, dates, calendars, time zones +

Extending chrono to Calendars and Time Zones + + P0355R7 + __cpp_lib_chrono >= 201803L

Miscellaneous minor fixes for chrono + + P1466R3 + __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 +

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 + + __cpp_lib_format >= 201907L +

Integration of chrono with text formatting + + P1361R2 + + __cpp_lib_format >= 201907L +

Printf corner cases in std::format + + P1652R1 + + __cpp_lib_format >= 201907L +

String Prefix and Suffix Checking - P0457R2 - - 9.1

Transformation Trait remove_cvref - - P0550R2 - - 9.1

nodiscard in the Library + 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 + __cpp_lib_generic_unordered_lookup >= 201811

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 + __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 + __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 - + P0600R1 9.1

de-pessimize legacy algorithms with std::move - P0616R0 - - 9.1

Utility to convert a pointer to a raw pointer - - P0653R2 - - 8.1

Atomic shared_ptr - - P0718R2 - -

Deprecate POD + P0616R0 + 9.1

Deprecate POD - P0767R1 - -

Library Support for the Spaceship (Comparison) Operator - - P0768R1 - -

Treating Unnecessary decay + P0767R1 + 10.1

Treating Unnecessary decay - P0777R1 - - 9.1

<span> - - P0122R7 - - 10.1 __cpp_lib_span >= 201803L

Extending chrono to Calendars and Time Zones - - P0355R7 - -

Thou Shalt Not Specialize std Function Templates! + P0777R1 + 9.1

Thou Shalt Not Specialize std Function Templates! - P0551R3 - -

Manipulators for C++ Synchronized Buffered Ostream - - P0753R2 - -

<version> - - P0754R2 - - 9.1

Comparing Unordered Containers - - P0809R0 - -

Constexpr iterator requirements - - P0858R0 - - 9.1 __cpp_lib_string_view >= 201803L - and __cpp_lib_array_constexpr >= 201803L

Symmetry for spaceship - - P0905R1 - -

string::reserve Should Not Shrink - - P0966R1 - -

Atomic Ref - - P0019R8 - - 10.1 __cpp_lib_atomic_ref >= 201806L

Checking for Existence of an Element in Associative Containers - - P0458R2 - - 9.1

LWG 2511: guaranteed copy elision for piecewise construction - - P0475R1 - - 7.1

Bit-casting object representations + P0551R3 +

Bit-casting object representations - P0476R2 - -

The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange - - P0528R3 - -

Support for contract based programming in C++ - - P0542R5 - -

Integral power-of-2 operations + P0476R2 + __cpp_lib_bit_cast >= 201806L

Integral power-of-2 operations - P0556R3 - - 9.1

Reviewing Deprecated Facilities of C++17 for C++20 + 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 - -

Improving the Return Value of Erase-Like Algorithms - - P0646R1 - - 9.1 __cpp_lib_list_remove_return_type >= 201806L

Efficient sized delete for variable sized classes - - P0722R3 - - 9.1 __cpp_lib_destroying_delete >= 201806L

Implicit conversion traits and utility functions - - P0758R1 - - 9.1

fpos Requirements + P0619R4 +

fpos Requirements - P0759R1 - - Note 1

Add shift to <algorithm> + P0759R1 + —

Add shift to <algorithm> - P0769R2 - -

Standard Library Specification in a Concepts and Contracts World + P0769R2 + 10.1 __cpp_lib_shift >= 201806L

Standard Library Specification in a Concepts and Contracts World - P0788R3 - -

Constexpr for swap and swap related functions - - P0879R0 - - 10.1 __cpp_lib_constexpr_algorithms >= 201806L

The identity metafunction - - P0887R1 - - 9.1

explicit(bool) + P0788R3 +

explicit(bool) - P0892R2 - - Note 1

Standard Library Concepts - - P0898R3 - - 10.1 __cpp_lib_concepts >= 201806L

Eradicating unnecessarily explicit default constructors from the standard library + P0892R2 + —

Eradicating unnecessarily explicit default constructors from the standard library - P0935R0 - - 9.1

Integrating feature-test macros into the C++ WD - - P0941R2 - - 5.1

constexpr comparison operators for std::array - - P1023R0 - - 10.1

Update The Reference To The Unicode Standard - - P1025R1 - -

Consistency improvements for <=> and other comparison operators - - P1120R0 - -

unwrap_ref_decay and unwrap_reference - - P0318R1 - - 9.1

Simplified partial function application + 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

reference_wrapper for incomplete types + 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

char8_t: A type for UTF-8 characters and strings - - P0482R6 - - 9.1 __cpp_lib_char8_t >= 201811L

Fixing operator>>(basic_istream&, CharT*) (LWG 2499) + P0357R3 + 9.1

Fixing operator>>(basic_istream&, CharT*) (LWG 2499) - P0487R1 - -

Utility functions to implement uses-allocator construction - - P0591R4 - - 9.1 - std::scoped_allocator_adaptor changes missing in 9.1.0 -

P0595R2 std::is_constant_evaluated() - - P0595R2 - - 9.1

variant and optional should propagate copy/move triviality + P0487R1 +

variant and optional should propagate copy/move triviality - P0602R4 - + P0602R4 8.3

A sane variant converting constructor - P0608R3 - + P0608R3 10.1

visit<R>: Explicit Return Type for visit - P0655R1 - - 9.1

std::function move constructor should be noexcept - - P0771R1 - - 7.2

The One Ranges Proposal - - P0896R4 - -

P0899R1 - LWG 3016 is not a defect + P0655R1 + 9.1

P0899R1 - LWG 3016 is not a defect - P0899R1 - - 7.1

Heterogeneous lookup for unordered containers - - P0919R3 - -

<chrono> zero(), min(), and max() should be noexcept - - P0972R0 - - 9.1

Constexpr in std::pointer_traits - - P1006R1 - - 9.1

std::assume_aligned - - P1007R3 - - 9.1

Smart pointer creation with default initialization - - P1020R1 - -

Misc constexpr bits - - P1032R1 - -

Should Span be Regular? - - P1085R2 - - 10.1 __cpp_lib_span >= 201902L

Editorial Guidance for merging P0019r8 and P0528r3 + P0899R1 + 7.1

Editorial Guidance for merging P0019r8 and P0528r3 - P1123R0 - - Note 1

Cleaning up Clause 20 + P1123R0 + —

Cleaning up Clause 20 - P1148R0 - -

Make stateful allocator propagation more consistent for operator+(basic_string) - - P1165R1 - - 10.1

Adopt Consistent Container Erasure from Library Fundamentals 2 for C++20 - - P1209R0 - - 9.1 __cpp_lib_erase_if >= 201811L

Completing the Rebase of Library Fundamentals, Version 3, Working Draft + P1148R0 +

Completing the Rebase of Library Fundamentals, Version 3, Working Draft - P1210R0 - -

Alternative Wording for P0907R4 Signed Integers are Two's Complement + P1210R0 +

Alternative Wording for P0907R4 Signed Integers are Two's Complement - P1236R1 - -

Remove CommonReference requirement from StrictWeakOrdering (a.k.a Fixing Relations) - - P1248R1 - -

Improving Completeness Requirements for Type Traits - - P1285R0 - - Partial

Well-behaved interpolation for numbers and pointers - - P0811R3 - - 9.1 __cpp_lib_interpolate >= 201902L

Missing feature test macros - - P1353R0 - - 9.1

- polymorphic_allocator<> - as a vocabulary type - - - P0339R6 - - 9.1

Making std::underlying_type SFINAE-friendly - - P0340R3 - - 9.1

+ P1236R1 + —

I Stream, You Stream, We All Stream for istream_iterator - P0738R2 - -

+ P0738R2 + 10.1

Mandating the Standard Library: Clause 16 - Language support library - P1458R1 - - Note 1

+ P1458R1 + —

Mandating the Standard Library: Clause 18 - Diagnostics library - P1459R1 - - Note 1

+ P1459R1 + —

Mandating the Standard Library: Clause 20 - Strings library - P1462R1 - - Note 1

+ P1462R1 + —

Mandating the Standard Library: Clause 21 - Containers library - P1463R1 - - 10

+ P1463R1 + 10.1

Mandating the Standard Library: Clause 22 - Iterators library - P1464R1 - + P1464R1

Make create_directory() Intuitive P1164R1 - 8.3 Treated as a DR for C++17

+ 8.3 Treated as a DR for C++17

Target Vectorization Policies from Parallelism V2 TS to C++20 - P1001R2 - -

Signed ssize() functions, unsigned size() functions - - P1227R2 - - 10.1

Ranges Design Cleanup - - P1252R2 - -

- Usability Enhancements for std::span - - - P1024R3 - - 10.1 __cpp_lib_span >= 201902L

Traits for [Un]bounded Arrays - - P1357R1 - - 9.1 __cpp_lib_bounded_array_traits >= 201902L

std::to_array - - P0325R4 - - 10.1 __cpp_lib_to_array >= 201907L

Bit operations + 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 - - 10.1 __cpp_lib_bitops >= 201907L

Mathematical constants + P0553R4 + 10.1 __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

Layout-compatibility and pointer-interconvertibility traits - - P0466R5 - - - __cpp_lib_is_layout_compatible >= 201907L, - __cpp_lib_is_layout_interconvertible >= 201907L, -

std::stop_token and std::jthread - - P0660R10 - - 10.1 __cpp_lib_jthread >= 201907L

Text formatting - - P0645R10 - - - __cpp_lib_format >= 201907L, -

constexpr std::invoke and related utilities - - P1065R2 - - 10.1 __cpp_lib_constexpr_invoke >= 201907L

constexpr std::allocator and related utilities - - P0784R7 - - 10.1 __cpp_constexpr_dynamic_alloc >= 201907L

Atomic waiting and notifying, std::semaphore, std::latch and std::barrier - - P1135R6 - - - __cpp_lib_atomic_lock_free_type_aliases >= 201907L in <atomic>, - __cpp_lib_atomic_flag_test >= 201907L in <atomic>, - __cpp_lib_atomic_wait >= 201907L in <atomic>, - __cpp_lib_semaphore >= 201907L in <semaphore>, - __cpp_lib_latch >= 201907L in <latch>, - __cpp_lib_barrier >= 201907L in <barrier> -

std::source_location + P0631R8 + 10.1 __cpp_lib_math_constants >= 201907L

std::source_location - P1208R6 - - - __cpp_lib_source_location >= 201907L, -

Adding <=> to the standard library - - P1614R2 - + P1208R6 - __cpp_lib_spaceship >= 201907L, + __cpp_lib_source_location >= 201907L

Efficient access to std::basic_stringbuf's Buffer - P0408R7 - + P0408R7

-Note 1: The changes in the proposal either do not affect the code in libstdc++, -or the changes are not required for conformance. -

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 202a draft. -

C++ TR1

+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. +

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 diff --git a/libstdc++-v3/doc/xml/manual/status_cxx2020.xml b/libstdc++-v3/doc/xml/manual/status_cxx2020.xml index 17f28887119..ade77cbb80b 100644 --- a/libstdc++-v3/doc/xml/manual/status_cxx2020.xml +++ b/libstdc++-v3/doc/xml/manual/status_cxx2020.xml @@ -1,8 +1,8 @@ -

-C++ 202a +C++ 2020 ISO C++ 2020 @@ -26,17 +26,20 @@ not in any particular release. The following table lists new library features that have been accepted into -the C++2a working draft. The "Proposal" column provides a link to the +the C++20 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). -The "SD-6 Feature Test" column shows the corresponding macro or header from +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++. +Feature-testing recommendations for C++ (where applicable) +or any notes about the implementation. - -C++ 2020 Implementation Status +

+C++ 2020 Library Features @@ -48,442 +51,755 @@ Feature-testing recommendations for C++. Library Feature Proposal Status - SD-6 Feature Test + SD-6 Feature Test / Notes - Endian just Endian + + Compile-time programming + + + + + Add constexpr modifiers to functions in <algorithm> and <utility> Headers - - P0463R1 - + + P0202R3 - 8.1 - + 10.1 + __cpp_lib_constexpr_algorithms >= 201703L - - Extending make_shared to Support Arrays + Constexpr for swap and swap related functions - - P0674R1 - + + P0879R0 - - + 10.1 + __cpp_lib_constexpr_algorithms >= 201806L - Floating Point Atomic + Constexpr for std::complex - - P0020R6 - + + P0415R1 + + 9.1 + __cpp_lib_constexpr_complex >= 201711L (since 9.4, see Note 1) + + + + P0595R2 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 - C++ Synchronized Buffered Ostream + Making std::string constexpr - - P0053R7 - + + P0980R1 - - + + __cpp_lib_constexpr_string >= 201907L - Add constexpr modifiers to functions in <algorithm> and <utility> Headers + + Making std::vector constexpr - - P0202R3 - + + P1004R2 - 10.1 - __cpp_lib_constexpr_algorithms >= 201703L + + __cpp_lib_constexpr_vector >= 201907L - Constexpr for std::complex + Constexpr in std::pointer_traits - - P0415R1 - + + P1006R1 9.1 - + __cpp_lib_constexpr_memory >= 201811L (since 9.4, see Note 1) - Make std::memory_order a scoped enumeration + constexpr for <numeric> algorithms - - P0439R0 - + + P1645R1 - 9.1 - + 10.1 + __cpp_lib_constexpr_numeric >= 201911L - String Prefix and Suffix Checking + Constexpr iterator requirements - - P0457R2 - + + 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 - + P0550R2 9.1 - + __cpp_lib_remove_cvref >= 201711L (since 9.4, see Note 1) - nodiscard in the Library + Implicit conversion traits and utility functions - - P0600R1 - + + 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 + + Partial - de-pessimize legacy algorithms with std::move + Missing feature test macros - - P0616R0 - + + P1353R0 9.1 - Utility to convert a pointer to a raw pointer + Making std::underlying_type SFINAE-friendly - - P0653R2 - + + P0340R3 - 8.1 + 9.1 + + Traits for [Un]bounded Arrays + + + P1357R1 + + 9.1 + __cpp_lib_bounded_array_traits >= 201902L + + - Atomic shared_ptr + Layout-compatibility and pointer-interconvertibility traits - - P0718R2 - + + P0466R5 + + + __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 + + - Deprecate POD + C++ Synchronized Buffered Ostream - - P0767R1 - + + P0053R7 - + __cpp_lib_syncbuf >= 201711L - Library Support for the Spaceship (Comparison) Operator + Manipulators for C++ Synchronized Buffered Ostream - - P0768R1 - + + P0753R2 - + __cpp_lib_syncbuf >= 201803L - Treating Unnecessary decay + Make std::memory_order a scoped enumeration - - P0777R1 - + + P0439R0 9.1 - <span> + + The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange - - P0122R7 - + + P0528R3 - 10.1 - __cpp_lib_span >= 201803L + + - Extending chrono to Calendars and Time Zones + Atomic shared_ptr - - P0355R7 - + + P0718R2 - + __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 - Thou Shalt Not Specialize std Function Templates! + Atomic waiting and notifying, std::semaphore, std::latch and std::barrier - - P0551R3 - + + P1135R6 + + + __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 - - Manipulators for C++ Synchronized Buffered Ostream + Ranges Design Cleanup - - P0753R2 - + + P1252R2 - + 10.1 + + - <version> + + Time, dates, calendars, time zones + + + + + + Extending chrono to Calendars and Time Zones - - P0754R2 - + + P0355R7 + + + __cpp_lib_chrono >= 201803L + + + + + Miscellaneous minor fixes for chrono + + + P1466R3 + + + __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 + + + - Comparing Unordered Containers + string::reserve Should Not Shrink - - P0809R0 - + + P0966R1 - Constexpr iterator requirements + char8_t: A type for UTF-8 characters and strings - - P0858R0 - + + P0482R6 9.1 - __cpp_lib_string_view >= 201803L - and __cpp_lib_array_constexpr >= 201803L + __cpp_lib_char8_t >= 201811L - - Symmetry for spaceship + char8_t backward compatibility remediation - - P0905R1 - + + P1423R3 - - + 10.1 + __cpp_lib_char8_t >= 201907L - string::reserve Should Not Shrink + Text formatting - - P0966R1 - + + P0645R10 - - - - - Atomic Ref - - P0019R8 - + __cpp_lib_format >= 201907L - 10.1 - __cpp_lib_atomic_ref >= 201806L - Checking for Existence of an Element in Associative Containers + + Integration of chrono with text formatting - - P0458R2 - + + P1361R2 - 9.1 - - - - - LWG 2511: guaranteed copy elision for piecewise construction + - - P0475R1 - + __cpp_lib_format >= 201907L - 7.1 - - Bit-casting object representations + Printf corner cases in std::format - - P0476R2 - + + P1652R1 - + + __cpp_lib_format >= 201907L + - - The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange + String Prefix and Suffix Checking - - P0528R3 - + + P0457R2 - - + 9.1 + __cpp_lib_starts_ends_with >= 201711L (since 9.4, see Note 1) - Support for contract based programming in C++ + Update The Reference To The Unicode Standard - - P0542R5 - + + P1025R1 + - Integral power-of-2 operations + + Containers + + + + + span: bounds-safe views for sequences of objects - - P0556R3 - + + P0122R7 - 9.1 - + 10.1 + __cpp_lib_span >= 201803L - - Reviewing Deprecated Facilities of C++17 for C++20 - - P0619R4 - + Usability Enhancements for std::span - - + + + P1024R3 + + 10.1 + __cpp_lib_span >= 201902L - Improving the Return Value of Erase-Like Algorithms + Should Span be Regular? - - P0646R1 - + + P1085R2 - 9.1 - __cpp_lib_list_remove_return_type >= 201806L + 10.1 + - Efficient sized delete for variable sized classes + Fixed-size <span> construction from dynamic range - - P0722R3 - + + P1976R2 - 9.1 - __cpp_lib_destroying_delete >= 201806L + 10.1 + __cpp_lib_span >= 202002L - Implicit conversion traits and utility functions + std::to_array - - P0758R1 - + + P0325R4 - 9.1 - + 10.1 + __cpp_lib_to_array >= 201907L - fpos Requirements + Checking for Existence of an Element in Associative Containers - - P0759R1 - + + P0458R2 - Note 1 + 9.1 - Add shift to <algorithm> + Comparing Unordered Containers - - P0769R2 - + + P0809R0 @@ -491,496 +807,470 @@ Feature-testing recommendations for C++. - Standard Library Specification in a Concepts and Contracts World + Heterogeneous lookup for unordered containers - - P0788R3 - + + P0919R3 - + __cpp_lib_generic_unordered_lookup >= 201811 - Constexpr for swap and swap related functions + Adopt Consistent Container Erasure from Library Fundamentals 2 for C++20 - - P0879R0 - + + P1209R0 - 10.1 - __cpp_lib_constexpr_algorithms >= 201806L + 9.1 + __cpp_lib_erase_if >= 201811L - The identity metafunction + Improving the Return Value of Erase-Like Algorithms - - P0887R1 - + + P0646R1 9.1 - + __cpp_lib_list_remove_return_type >= 201806L - explicit(bool) + Improving the Return Value of Erase-Like Algorithms II: Free erase/erase_if - - P0892R2 - + + P1115R3 + + 9.1 + + + __cpp_lib_erase_if >= 202002L + (defined to 201900L for GCC 9.1 and 9.2 so use > 201811L) + - Note 1 - - Standard Library Concepts + Signed ssize() functions, unsigned size() functions - - P0898R3 - + + P1227R2 10.1 - __cpp_lib_concepts >= 201806L + __cpp_lib_ssize >= 201902L + - Eradicating unnecessarily explicit default constructors from the standard library - - - P0935R0 - + + Memory management - 9.1 - - Integrating feature-test macros into the C++ WD + Utility to convert a pointer to a raw pointer - - P0941R2 - + + P0653R2 - 5.1 - + 8.1 + __cpp_lib_to_address >= 201711L (since 9.4, see Note 1) - constexpr comparison operators for std::array + + Extending make_shared to Support Arrays - - P1023R0 - + + P0674R1 - 10.1 - + + __cpp_lib_shared_ptr_arrays >= 201707L - - Update The Reference To The Unicode Standard + Efficient sized delete for variable sized classes - - P1025R1 - + + P0722R3 - - + 9.1 + __cpp_lib_destroying_delete >= 201806L - - Consistency improvements for <=> and other comparison operators + Utility functions to implement uses-allocator construction - - P1120R0 - + + P0591R4 + + 9.1 + + std::scoped_allocator_adaptor changes missing in 9.1.0 - - - unwrap_ref_decay and unwrap_reference + std::assume_aligned - - P0318R1 - + + P1007R3 9.1 - + __cpp_lib_assume_aligned >= 201811L (since 9.4, see Note 1) - Simplified partial function application + + Smart pointer creation with default initialization - - P0356R5 - + + P1020R1 - 9.1 - __cpp_lib_bind_front >= 201811L + + __cpp_lib_smart_ptr_for_overwrite >= 201811L - reference_wrapper for incomplete types + Make stateful allocator propagation more consistent for operator+(basic_string) - - P0357R3 - + + P1165R1 - 9.1 + 10.1 - char8_t: A type for UTF-8 characters and strings - - P0482R6 - + polymorphic_allocator<> as a vocabulary type + + + + P0339R6 9.1 - __cpp_lib_char8_t >= 201811L + + __cpp_lib_polymorphic_allocator >= 201902L (since 9.4, see Note 1) + - - Fixing operator>>(basic_istream&, CharT*) (LWG 2499) + LWG 2511: guaranteed copy elision for piecewise construction - - P0487R1 - + + P0475R1 - + 7.1 + - Utility functions to implement uses-allocator construction - - - P0591R4 - - - 9.1 - - std::scoped_allocator_adaptor changes missing in 9.1.0 + + Miscellaneous - P0595R2 std::is_constant_evaluated() + nodiscard in the Library - - P0595R2 - + + P0600R1 9.1 - variant and optional should propagate copy/move triviality + de-pessimize legacy algorithms with std::move - - P0602R4 - + + P0616R0 - 8.3 + 9.1 - A sane variant converting constructor + Deprecate POD - - P0608R3 - + + P0767R1 10.1 - visit<R>: Explicit Return Type for visit + Treating Unnecessary decay - - P0655R1 - + + P0777R1 9.1 - std::function move constructor should be noexcept + + Thou Shalt Not Specialize std Function Templates! - - P0771R1 - + + P0551R3 - 7.2 + - The One Ranges Proposal + Bit-casting object representations - - P0896R4 - + + P0476R2 - + __cpp_lib_bit_cast >= 201806L - P0899R1 - LWG 3016 is not a defect + Integral power-of-2 operations - - P0899R1 - + + P0556R3 - 7.1 - + 9.1 + __cpp_lib_int_pow2 >= 201806L (since 9.4, see Note 1) - - Heterogeneous lookup for unordered containers + On the names of low-level bit manipulation functions - - P0919R3 - + + P1956R1 - - + 10.1 + __cpp_lib_int_pow2 >= 202002L - <chrono> zero(), min(), and max() should be noexcept + Safe integral comparisons - - P0972R0 - + + P0586R2 - 9.1 - + 10.1 + __cpp_lib_integer_comparison_functions >= 202002L - Constexpr in std::pointer_traits + + Reviewing Deprecated Facilities of C++17 for C++20 - - P1006R1 - + + P0619R4 - 9.1 + - std::assume_aligned + fpos Requirements - - P1007R3 - + + P0759R1 - 9.1 + — - Smart pointer creation with default initialization + Add shift to <algorithm> - - P1020R1 - + + P0769R2 - - + 10.1 + __cpp_lib_shift >= 201806L - Misc constexpr bits + Standard Library Specification in a Concepts and Contracts World - - P1032R1 - + + P0788R3 - Should Span be Regular? + explicit(bool) - - P1085R2 - + + P0892R2 - 10.1 - __cpp_lib_span >= 201902L + — + - Editorial Guidance for merging P0019r8 and P0528r3 + Eradicating unnecessarily explicit default constructors from the standard library - - P1123R0 - + + P0935R0 - Note 1 + 9.1 - - Cleaning up Clause 20 + std::function move constructor should be noexcept - - P1148R0 - + + P0771R1 - + 7.2 - Make stateful allocator propagation more consistent for operator+(basic_string) + Simplified partial function application - - P1165R1 - + + P0356R5 - 10.1 - + 9.1 + __cpp_lib_bind_front >= 201811L - Adopt Consistent Container Erasure from Library Fundamentals 2 for C++20 + bind_front should not unwrap reference_wrapper - - P1209R0 - + + P1651R0 - 9.1 - __cpp_lib_erase_if >= 201811L + 9.3 + __cpp_lib_bind_front >= 201907L - - Completing the Rebase of Library Fundamentals, Version 3, Working Draft + reference_wrapper for incomplete types - - P1210R0 - + + P0357R3 - + 9.1 - Alternative Wording for P0907R4 Signed Integers are Two's Complement + Fixing operator>>(basic_istream&, CharT*) (LWG 2499) - - P1236R1 - + + P0487R1 - - Remove CommonReference requirement from StrictWeakOrdering (a.k.a Fixing Relations) + variant and optional should propagate copy/move triviality - - P1248R1 - + + P0602R4 - + 8.3 - - Improving Completeness Requirements for Type Traits + A sane variant converting constructor - - P1285R0 - + + P0608R3 - Partial + 10.1 - Well-behaved interpolation for numbers and pointers + visit<R>: Explicit Return Type for visit - - P0811R3 - + + P0655R1 9.1 - __cpp_lib_interpolate >= 201902L + - Missing feature test macros + P0899R1 - LWG 3016 is not a defect - - P1353R0 - + + P0899R1 - 9.1 + 7.1 + Editorial Guidance for merging P0019r8 and P0528r3 - polymorphic_allocator<> - as a vocabulary type + + P1123R0 + — + + + + + + Cleaning up Clause 20 - - P0339R6 - + + P1148R0 - 9.1 + - Making std::underlying_type SFINAE-friendly + + Completing the Rebase of Library Fundamentals, Version 3, Working Draft - - P0340R3 - + + P1210R0 - 9.1 + - + Alternative Wording for P0907R4 Signed Integers are Two's Complement + + + P1236R1 + + — + + + + I Stream, You Stream, We All Stream for istream_iterator - P0738R2 - + P0738R2 - + 10.1 @@ -991,11 +1281,10 @@ Feature-testing recommendations for C++. - P1458R1 - + P1458R1 - - Note 1 + — + @@ -1005,11 +1294,10 @@ Feature-testing recommendations for C++. - P1459R1 - + P1459R1 - - Note 1 + — + @@ -1019,11 +1307,10 @@ Feature-testing recommendations for C++. - P1462R1 - + P1462R1 - - Note 1 + — + @@ -1033,10 +1320,9 @@ Feature-testing recommendations for C++. - P1463R1 - + P1463R1 - 10 + 10.1 @@ -1048,8 +1334,7 @@ Feature-testing recommendations for C++. - P1464R1 - + P1464R1 @@ -1060,212 +1345,84 @@ Feature-testing recommendations for C++. P1164R1 - + 8.3 Treated as a DR for C++17 - Target Vectorization Policies from Parallelism V2 TS to C++20 - P1001R2 - + P1001R2 - - + 9.1 + __cpp_lib_execution >= 201902L (since 9.4, see Note 1) - Signed ssize() functions, unsigned size() functions + Merge Coroutines TS into C++20 working draft - - P1227R2 - + + P0912R5 10.1 - + __cpp_lib_coroutines >= 201902L - - Ranges Design Cleanup + Endian just Endian - - P1252R2 - + + P0463R1 - - + 8.1 + __cpp_lib_endian >= 201907L + Bit operations - Usability Enhancements for std::span - - - - P1024R3 - + + P0553R4 10.1 - __cpp_lib_span >= 201902L + __cpp_lib_bitops >= 201907L (since 9.4, see Note 1) - Traits for [Un]bounded Arrays + Well-behaved interpolation for numbers and pointers - - P1357R1 - + + P0811R3 9.1 - __cpp_lib_bounded_array_traits >= 201902L - - - - std::to_array - - - P0325R4 - - - 10.1 - __cpp_lib_to_array >= 201907L - - - - Bit operations - - - P0553R4 - - - 10.1 - __cpp_lib_bitops >= 201907L + __cpp_lib_interpolate >= 201902L Mathematical constants - P0631R8 - + P0631R8 10.1 __cpp_lib_math_constants >= 201907L - - - Layout-compatibility and pointer-interconvertibility traits - - - P0466R5 - - - - - __cpp_lib_is_layout_compatible >= 201907L, - __cpp_lib_is_layout_interconvertible >= 201907L, - - - - - std::stop_token and std::jthread - - - P0660R10 - - - 10.1 - __cpp_lib_jthread >= 201907L - - - - - Text formatting - - - P0645R10 - - - - - __cpp_lib_format >= 201907L, - - - - - constexpr std::invoke and related utilities - - - P1065R2 - - - 10.1 - __cpp_lib_constexpr_invoke >= 201907L - - - - constexpr std::allocator and related utilities - - - P0784R7 - - - 10.1 - __cpp_constexpr_dynamic_alloc >= 201907L - - - - - Atomic waiting and notifying, std::semaphore, std::latch and std::barrier - - - P1135R6 - - - - - __cpp_lib_atomic_lock_free_type_aliases >= 201907L in <atomic>, - __cpp_lib_atomic_flag_test >= 201907L in <atomic>, - __cpp_lib_atomic_wait >= 201907L in <atomic>, - __cpp_lib_semaphore >= 201907L in <semaphore>, - __cpp_lib_latch >= 201907L in <latch>, - __cpp_lib_barrier >= 201907L in <barrier> - - - std::source_location - P1208R6 - - - - - __cpp_lib_source_location >= 201907L, - - - - - - Adding <=> to the standard library - - - P1614R2 - + P1208R6 - __cpp_lib_spaceship >= 201907L, + __cpp_lib_source_location >= 201907L @@ -1274,8 +1431,7 @@ Feature-testing recommendations for C++. Efficient access to std::basic_stringbuf's Buffer - P0408R7 - + P0408R7 @@ -1286,23 +1442,9 @@ Feature-testing recommendations for C++.

-Note 1: The changes in the proposal either do not affect the code in libstdc++, -or the changes are not required for conformance. +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. - -

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 202a draft. - - - -

Part I. Introduction -

Chapter 1. Status

Implementation Status

C++ 1998/2003

Implementation Status

Chapter 1. Status

Implementation Status

C++ 1998/2003

Implementation Status

C++ 202a

C++ 2020

Implementation Specific Behavior

C++ TR1

C++ TR1