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C++20

From cppreference.com
< cpp

The current revision of the C++ standard

Contents

[edit] New language features

[edit] New library features

[edit] New headers

in Thread support library:

[edit] Library features

[edit] Defect reports

Defect Reports fixed in C++20 (158 core, 345 library)

[edit] Compiler support

Main Article: C++ compiler support

[edit] C++20 core language features

C++20 feature
 
Paper(s)
 
GCC
Clang
MSVC
Apple Clang
EDG eccp
Intel C++
IBM XLC++
Sun/Oracle C++
Embarcadero C++ Builder
Cray
Nvidia HPC C++
(ex Portland Group/PGI)
Nvidia nvcc
Allow lambda-capture [=, this] P0409R2 8 6 19.22*

10.0.0*

5.1 20.7
__VA_OPT__ P0306R4
P1042R1
8 (partial)*
10 (partial)*
12
9 19.25*

11.0.3*

5.1 20.7
Designated initializers P0329R4 4.7 (partial)*
8
3.0 (partial)*
10
19.21* (partial)* 5.1 20.7
template-parameter-list for generic lambdas P0428R2 8 9 19.22*

11.0.0*

5.1 20.7
Default member initializers for bit-fields P0683R1 8 6 19.25*

10.0.0*

5.1 20.7
Initializer list constructors in class template argument deduction P0702R1 8 6 19.14* Yes 5.0 20.7
const&-qualified pointers to members P0704R1 8 6 19.0 (2015)*

10.0.0*

5.1 20.7
Concepts P0734R0 6
(TS only)
10
10 19.23* (partial)*
19.30*

12.0.0* (partial)

6.1 20.11
Lambdas in unevaluated contexts P0315R4 9 13 (partial)*
14 (partial)*
19.28 (16.8)*
Three-way comparison operator P0515R3 10 8 (partial)
10
19.20* 5.1 20.7
DR: Simplifying implicit lambda capture P0588R1 8 19.24* 5.1 20.7
init-statements for range-based for P0614R1 9 8 19.25*

11.0.0*

6.0 20.11
Default constructible and assignable stateless lambdas P0624R2 9 8 19.22*

10.0.1*

5.1 20.7
const mismatch with defaulted copy constructor P0641R2 9 8 19.0 (2015)*

10.0.1*

5.1 20.7
Access checking on specializations P0692R1 Yes 8 (partial)
14
19.26*

10.0.1* (partial)

5.1 20.7
ADL and function templates that are not visible P0846R0 9 9 19.21*

11.0.3*

5.1 20.7
DR: Specify when constexpr function definitions are needed for constant evaluation P0859R0 5.2 (partial)*
9
8 19.27* (partial)*
19.31*
Attributes [[likely]] and [[unlikely]] P0479R5 9 12 19.26*

13.0.0*

5.1 20.7
Make typename more optional P0634R3 9 19.29 (16.10)* 5.1 20.7
Pack expansion in lambda init-capture P0780R2 9 9 19.22*

11.0.3*

6.1 20.11
Attribute [[no_unique_address]] P0840R2 9 9 19.28 (16.9)**

11.0.3*

5.1 20.7
Conditionally Trivial Special Member Functions P0848R3 10 19.28 (16.8)* 6.1 20.11
DR: Relaxing the structured bindings customization point finding rules P0961R1 8 8 19.21*

10.0.1*

5.1 20.7
DR: Relaxing the range-for loop customization point finding rules P0962R1 8 8 19.25* 5.1 20.7
DR: Allow structured bindings to accessible members P0969R0 8 8 19.21*

10.0.1*

5.1 20.7
Destroying operator delete P0722R3 9 6 19.27*

10.0.0*

6.1 20.11
Class types in non-type template parameters P0732R2 9 12 (partial) 19.26*(partial)*
19.28 (16.9)*
6.2
Deprecate implicit capture of this via [=] P0806R2 9 7 19.22* 5.1 20.7
explicit(bool) P0892R2 9 9 19.24*

11.0.3*

5.1 20.7
Integrating feature-test macros P0941R2 5 3.4 19.15* (partial)
19.20*
Yes 5.0 20.7
Prohibit aggregates with user-declared constructors P1008R1 9 8 19.20*

10.0.1*

5.1 20.7
constexpr virtual function P1064R0 9 9 19.28 (16.9)*

11.0.3*

5.1 20.7
Consistency improvements for comparisons P1120R0 10 8 (partial)
10
19.22*

10.0.1* (partial)

5.1 20.7
char8_t P0482R6 9 7 19.22*

10.0.0*

5.1 20.7
std::is_constant_evaluated() P0595R2 9 9 19.25*

11.0.3*

5.1 19.1
constexpr try-catch blocks P1002R1 9 8 19.25*

10.0.1*

5.1 20.7
Immediate functions (consteval) P1073R3 10 (partial)*
11
11 (partial)
14 (partial)*
19.28 (16.8)**
(partial)
19.29 (16.10)*
5.1 20.7
Nested inline namespaces P1094R2 9 8 19.27*

10.0.1*

5.1 20.7
Yet another approach for constrained declarations P1141R2 10 10 19.26* (partial)
19.28 (16.9)*
6.1 20.11
Signed integers are two's complement P1236R1 9 9 Yes

11.0.3*

N/A yes
dynamic_cast and polymorphic typeid in constant expressions P1327R1 10 9 19.29 (16.10)*

11.0.3*

5.1 20.7
Changing the active member of a union inside constexpr P1330R0 9 9 19.10*

11.0.3*

5.1 20.7
Coroutines P0912R5 10 8 (partial) 19.0 (2015)* (partial)
19.10* (TS only)
19.28 (16.8)*

10.0.1* (partial)

5.1
Parenthesized initialization of aggregates P0960R3 10 19.28 (16.8)* 5.1 20.7
DR: Array size deduction in new-expressions P1009R2 11 9 19.27*

11.0.3*

5.1 20.7
Modules P1103R3 11 (partial) 8 (partial) 19.0 (2015)* (partial)
19.10* (TS only)
19.28 (16.8)*

10.0.1* (partial)

Stronger Unicode requirements P1041R4
P1139R2
10 Yes 19.0 (2015)* (P1041R4)
19.26* (P1139R2)
Yes N/A
<=> != == P1185R2 10 10 19.22* 5.1 20.7
DR: Explicitly defaulted functions with different exception specifications P1286R2 10 9 19.28 (16.8)*

11.0.3*

5.1 20.7
Lambda capture and storage class specifiers of structured bindings P1091R3
P1381R1
10 8 (partial) 19.11*(P1381R1)
19.24*(P1091R3)

10.0.1* (partial)

5.1 20.7
Permit conversions to arrays of unknown bound P0388R4 10 14 19.27* 6.0 20.11
constexpr container operations P0784R7 10 10 19.28 (16.9)* 6.0 20.11
Deprecating some uses of volatile P1152R4 10 10 19.27* 6.0 20.11
constinit P1143R2 10 10 19.29 (16.10)* 6.1 20.11
Deprecate comma operator in subscripts P1161R3 10 9 19.25*

11.0.3*

6.0 20.11
[[nodiscard]] with message P1301R4 10 9 19.25*

11.0.3*

6.0 20.11
Trivial default initialization in constexpr functions P1331R2 10 10 19.27* 6.1 20.11
Unevaluated asm-declaration in constexpr functions P1668R1 10 10 19.28 (16.9)* 6.1 20.11
using enum P1099R5 11 13 19.24* 6.3
Synthesizing three-way comparison for specified comparison category P1186R3 11 10 19.24* 6.0 20.11
DR: [[nodiscard]] for constructors P1771R1 10 9 19.24*

11.0.3*

6.0 20.11
Class template argument deduction for alias templates P1814R0 10 19.27*
Class template argument deduction for aggregates P1816R0
P2082R1
10(P1816R0)
11(P2082R1)
19.27*
DR: Implicit move for more local objects and rvalue references P1825R0 11* 13 19.24* 6.0 20.11
Allow defaulting comparisons by value P1946R0 10 10 19.25* 6.1 20.11
Remove std::weak_equality and std::strong_equality P1959R0 10 10 19.25* 6.1 20.11
Inconsistencies with non-type template parameters P1907R1 10 (partial)
11
12 (partial) 19.26* 6.2
DR: Pseudo-destructors end object lifetimes P0593R6 11 11 Yes N/A
DR: Converting from T* to bool should be considered narrowing P1957R2 10*
11*
11 19.27* 6.1
C++20 feature
 
Paper(s)
 
GCC
Clang
MSVC
Apple Clang
EDG eccp
Intel C++
IBM XLC++
Sun/Oracle C++
Embarcadero C++ Builder
Cray
Nvidia HPC C++
Nvidia nvcc

[edit] C++20 library features

C++20 feature
 
Paper(s)
 
GCC libstdc++
Clang libc++
MSVC STL
Apple Clang
Sun/Oracle C++
Standard Library
Embarcadero C++ Builder
Standard Library
Cray C++
Standard Library
std::endian P0463R1 8 7 19.22*

10.0.0*

Extending std::make_shared() to support arrays P0674R1 19.27*
Floating-point atomic P0020R6 10 19.22*
Synchronized buffered (std::basic_osyncstream) P0053R7 11 19.29 (16.10)*
constexpr for <algorithm> and <utility> P0202R3 10 8 (partial)
12
19.26*

10.0.1* (partial)
12.0.5*

More constexpr for <complex> P0415R1 9 7 (partial) 19.27*

10.0.0* (partial)

Make std::memory_order a scoped enumeration P0439R0 9 9 19.25*

11.0.3*

String prefix and suffix checking: string(_view) ::starts_with/ends_with P0457R2 9 6 19.21*

10.0.0*

Library support for operator<=> <compare> P0768R1 10 7 (partial)
12
19.20* (partial)
19.28 (16.9)*

10.0.0* (partial)

std::remove_cvref P0550R2 9 6 19.20*

10.0.0*

[[nodiscard]] in the standard library P0600R1 9 7 (partial) 19.13* (partial)
19.22*

10.0.0* (partial)

Using std::move in numeric algorithms P0616R0 9 12 19.23*
Utility to convert a pointer to a raw pointer P0653R2 8 6 19.22* Yes
Atomic std::shared_ptr and std::weak_ptr P0718R2 19.27*
std::span P0122R7 10 7 19.26*

10.0.0*

Calendar and timezone P0355R7 11 (partial) 7 (partial) 19.29 (16.10)*

10.0.0* (partial)

<version> P0754R2 9 7 19.22*

10.0.0*

Comparing unordered containers P0809R0 Yes Yes 16.0* Yes
ConstexprIterator requirements P0858R0 9 12 19.11*
std::basic_string::reserve() should not shrink P0966R1 11 8 19.25*

10.0.1*

Atomic Compare-And-Exchange with padding bits P0528R3 19.28 (16.8)*
std::atomic_ref P0019R8 10 19.28 (16.8)*
contains() member function of associative containers, e.g. std::map::contains() P0458R2 9 9 (partial)*
13
19.21*

11.0.3*

DR: Guaranteed copy elision for piecewise construction P0475R1 9 Yes 19.29 (16.10)* Yes
std::bit_cast() P0476R2 11 14 19.27*
Integral power-of-2 operations:

std::bit_ceil(), std::bit_floor(), std::bit_width(), std::has_single_bit()

P0556R3 P1956R1 9 (P0556R3)
10 (P1956R1)
9 (P0556R3)
12 (P1956R1)
19.25* (P0556R3)*
19.27* (P1956R1)*
19.28 (16.8)*
Improving the return value of erase-like algorithms P0646R1 9 10 19.21*
std::destroying_delete P0722R3 9 9 19.27*

11.0.3*

std::is_nothrow_convertible P0758R1 9 9 19.23*

11.0.3*

Add std::shift_left/right to <algorithm> P0769R2 10 12 19.21*
Constexpr for std::swap() and swap related functions P0879R0 10 12 (partial)
13
19.26*
std::type_identity P0887R1 9 8 19.21*

10.0.1*

Concepts library P0898R3 10 13 19.23*

12.0.0* (partial)

constexpr comparison operators for std::array P1023R0 10 8 19.27*

10.0.1*

std::unwrap_ref_decay and std::unwrap_reference P0318R1 9 8 19.21*

10.0.1*

std::bind_front() P0356R5 9 13 19.25*
std::reference_wrapper for incomplete types P0357R3 9 8 19.26*

10.0.1*

Fixing operator>>(basic_istream&, CharT*) P0487R1 11 8 19.23*

10.0.1*

Library support for char8_t P0482R6 9 8 (partial)*
19.22*
Utility functions to implement uses-allocator construction P0591R4 9 19.29 (16.10)*
DR: std::variant and std::optional should propagate copy/move triviality P0602R4 8.3 8 19.11*

10.0.1*

A sane std::variant converting constructor P0608R3 10 9 19.29 (16.10)*

11.0.3*

std::function's move constructor should be noexcept P0771R1 7.2 6 19.22* Yes
The One Ranges Proposal P0896R4 10 13 (partial) 19.29 (16.10)*
Heterogeneous lookup for unordered containers P0919R3 P1690R1 11 12 19.23* (P0919R3)
19.25* (P1690R1)
<chrono> zero(), min(), and max() should be noexcept P0972R0 9 8 19.14*

10.0.1*

constexpr in std::pointer_traits P1006R1 9 8 19.26*

10.0.1*

std::assume_aligned() P1007R3 9*
11
19.28 (16.9)*
Smart pointer creation with default initialization (e.g. make_unique_for_overwrite) P1020R1
P1973R1
19.28 (16.9)*
Misc constexpr bits P1032R1 10 13 19.28 (16.8)*
Remove comparison operators of std::span P1085R2 10 8 19.26*

10.0.1*

Make stateful allocator propagation more consistent for operator+(basic_string) P1165R1 10 19.26*
Consistent container erasure, e.g. std::erase(std::vector), or std::erase_if(std::map) P1209R0 P1115R3 9 (P1209R0)
10 (P1115R3)
8 (P1209R0)
11 (P1115R3)
19.25* (P1209R0)
19.27* (P1115R3)

10.0.1* (P1209R0)

Standard library header units P1502R1 11 19.29 (16.10)*
polymorphic_allocator<> as a vocabulary type P0339R6 9 19.28 (16.9)*
std::execution::unseq P1001R2 9 19.28 (16.8)*
std::lerp() and std::midpoint() P0811R3 9 9 19.23* (partial)
19.28 (16.8)*

11.0.3*

Usability enhancements for std::span P1024R3 10 9*
14
19.26*

11.0.3*

DR: Make create_directory() intuitive P1164R1 8.3 12 19.20*
std::ssize() and unsigned extent for std::span P1227R2 10 9 19.25*

11.0.3*

Traits for (un)bounded arrays P1357R1 9 9 19.25*

11.0.3*

std::to_array() P0325R4 10 10 19.25*
Efficient access to std::basic_stringbuf’s buffer P0408R7 11 19.29 (16.10)*
Layout-compatibility and pointer-interconvertibility traits P0466R5 12 19.29 (16.10)**
Bit operations: std::

rotl(), rotr(), countl_zero(), countl_one(), countr_zero(), countr_one(), popcount()

P0553R4 9 9 19.25**
19.28 (16.8)*

11.0.3*

Mathematical constants P0631R8 10 11 19.25*
Text formatting P0645R10 14 (partial)* 19.29 (16.10)*
std::stop_token and std::jthread P0660R10 10 19.28 (16.9)*
constexpr std::allocator and related utilities P0784R7 10 12 19.29 (16.10)*
constexpr std::string P0980R1 12 19.29 (16.10)*
19.30**


constexpr std::vector P1004R2 12 19.29 (16.10)*
19.30**


Input range adaptors P1035R7 10 19.29 (16.10)*
constexpr std::invoke() and related utilities P1065R2 10 12 19.28 (16.8)*
Atomic waiting and notifying, std::counting_semaphore, std::latch and std::barrier P1135R6 11 11 19.28 (16.8)*
std::source_location P1208R6 11 19.29 (16.10)*
Adding <=> to the standard library P1614R2 10 14 19.29 (16.10)*
constexpr default constructor of std::atomic and std::atomic_flag P0883R2 10 13 19.26*
constexpr for numeric algorithms P1645R1 10 12 19.26*
Safe integral comparisons P0586R2 10 13 19.27*
C++20 feature
 
Paper(s)
 
GCC libstdc++
Clang libc++
MSVC STL
Apple Clang
Sun/Oracle C++
Standard Library
Embarcadero C++ Builder
Standard Library
Cray C++
Standard Library

* - hover over the version number to see notes