Difference between revisions of "C++20"

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(Mark as usable std::make_unique_for_overwrite, ranges and heterogenous lookup)
 
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See also [[C++11]], [[C++17]].
See also [[C++11]], [[C++17]], [[C++23]].


Some things that will be interesting to use once C++20 is common:
Some things that will be interesting to use once C++20 is common:
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! Feature                          !! Since !! Can use?                                    !! GCC    !! Apple Clang !! Comment
! Feature                          !! Since !! Can use?                                    !! GCC    !! Apple Clang !! Comment
|-
|-
| <code>std::span</code>            || C++20 || style="background: lightgreen;" | from 1.3? || 10    || 11.0.3 || Handle buffers like standard library containers without risk of overflow.
| <code>std::span</code>            || C++20 || style="background: lightgreen;" | from 1.4  || 10    || 11.0.3 || Handle buffers like standard library containers without risk of overflow.
|-
|-
| <code>std::format</code>          || C++20 || style="background: pink;"       |           || 13    || N/A    || Better and more efficient formatting of strings. [https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0645r10.html Text Formatting]
| <code>std::format</code>          || C++20 || style="background: lightgreen;" | from 1.5 || 13    || 15.3  || Better and more efficient formatting of strings. [https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0645r10.html Text Formatting]
|-
|-
| <code>std::lerp</code>            || C++20 || style="background: lightgreen;" | from 1.4? ||  9    || 11.0.3 || Linear interpolation. (ui/tools/pencil-tool.cpp)
| <code>std::lerp</code>            || C++20 || style="background: lightgreen;" | from 1.4 ||  9    || 11.0.3 || Linear interpolation. (ui/tools/pencil-tool.cpp)
|-
|-
| <code>std::bit_floor</code>      || C++20 || style="background: lightgreen;" | from 1.4? || 9/10  || 11.0.3/13.0.0 || Compute floor(log2(x)). (helper/mathfns.h)
| <code>std::bit_floor</code>      || C++20 || style="background: lightgreen;" | from 1.4 || 9/10  || 11.0.3/13.0.0 || Compute <code>floor(log2(x))</code>. (helper/mathfns.h)
|-
|-
| <code>Concepts</code>            || C++20 ||                                   from 1.4? || 6/10  || 12.0.0 Partial || Safer templating. (ui/controller.h)
| Concepts                         || C++20 || style="background: lightgreen;" | from 1.5 || 6/10  || 12.0.0 Partial || Safer templating. (ui/controller.h)
|-
|-
| <code>Coroutines</code>          || C++20 ||                                             || 10    || 10.0.1 Partial || Simpler asynchronous code. (trace/trace.cpp)
| Coroutines                       || C++20 || style="background: lightgreen;" | from 1.5 || 10    || 10.0.1 Partial,<br/> 15.3 Full || Simpler asynchronous code. (trace/trace.cpp)
|-
|-
| <code>std::make_unique_for_overwrite</code> || C++20 || style="background: pink;" |       || 11    || N/A    || Don't zero arrays allocated using std::make_unique. (util/pool.cpp)
| <code>std::make_unique_for_overwrite</code>
                                    || C++20 || style="background: lightgreen;" | from 1.5 || 11    || 15.0.0 || Don't zero arrays allocated using std::make_unique. (util/pool.cpp)
|-
|-
| <code>Ranges</code>              || C++20 ||                                   from 1.4? ||        || ?     || for (init; decl : expr). (ui/dialog/swatches.cpp)
| Ranges                           || C++20 || style="background: lightgreen;" | from 1.5 ||        || ? || (ui/dialog/swatches.cpp)
|-
|-
| <code>[https://stackoverflow.com/a/60244416/5075760 Structural templates]</code> || C++20 || from 1.4? ||   || Partial     || Allow instances of arbitrary literal classes as template parameters. (display/drawing.cpp)
| [https://stackoverflow.com/a/60244416/5075760 Structural templates]
                                    || C++20 ||                                   from 1.4? ||       || Partial || Allow instances of arbitrary literal classes as template parameters. (display/drawing.cpp)
|-
| Mathematical Constants            || C++20 ||                                            || 10    || 12.0.5 || Constants like <code>std::numbers::pi</code>.
|-
| Heterogenous lookup in <code>std::unordered_map</code>
                                    || C++20 || style="background: lightgreen;" | from 1.5 ||        ||        || Faster lookup, use of smart pointers as keys.
|-
|<code>consteval static</code> member functions
|C++20
| style="background: pink;" | not yet
|
|
|Guaranteed compile time evaluation of member functions (stronger than <code>constexpr</code>)
|}
 
References:
 
* General: https://en.cppreference.com/w/Template:cpp/compiler_support/20
* Apple Clang: https://developer.apple.com/documentation/xcode-release-notes
 
As of 21 September 2025, the CI runners for the various supported platforms are
* Linux: GCC 13.3.0 (on Ubuntu 24.04)
* Windows: GCC 15.1.0
* macOS: Apple Clang 17.0.0
* Android: Clang 19.0.0 (on Ubuntu 24.04)
 
We support the latest Debian stable and latest Ubuntu LTS.
{| class="wikitable"
|-
! Distro                        || gcc    || clang  || glib || glibmm || gtk4 || gtkmm4
|-
| Debian 13 (Trixie)            || 14.2.0 || 19.0  || 2.84.4 || 2.84.0 || 4.18.6 || 4.18.0
|-
| Ubuntu 24.04 (Noble)          || 13.3.0 || 18.1.3 || 2.80.0 || 2.78.1 || 4.14.2 || style="background: wheat;" | 4.10.1
|}
|}


As of 1 September 2023, the CI runners for:
The build requires glibmm >= 2.78.1 and gtkmm4 >= 4.14, however Inkscape will compile its own gtkmm4 if the system version is too old, so building on Ubuntu 24.04 still works out of the box.
* Linux:
** appimage:linux GNU 9.4.0 (Using Ubuntu 20.04)
** inkscape:linux GNU 11.4.0
* Windows
** inkscape:windows:build Gnu 13.1.0
** inkscape:windows:dist Same as above.
* macOS:
** inkscape::macos:arm Apple Clang 13.1.6
** inkscape:macos:x64: Apple Clang 14.0.0.


Errors and Deprecated items that we use:
Deprecated items that we still use:
* error: call of overloaded ‘lerp(double, double&, double&)’ is ambiguous  (ui/knot/knot-holder-entity.cpp)
* warning: implicit capture of ‘this’ via ‘[=]’ is deprecated in C++20 [-Wdeprecated] https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0806r2.html
* warning: implicit capture of ‘this’ via ‘[=]’ is deprecated in C++20 [-Wdeprecated] https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0806r2.html
* warning: bitwise operation between different enumeration types ‘Box3D::Axis’ and ‘Box3D::FrontOrRear’ is deprecated [-Wdeprecated-enum-enum-conversion]
* warning: bitwise operation between different enumeration types ‘Box3D::Axis’ and ‘Box3D::FrontOrRear’ is deprecated [-Wdeprecated-enum-enum-conversion]

Latest revision as of 21:16, 21 September 2025

See also C++11, C++17, C++23.

Some things that will be interesting to use once C++20 is common:

Feature Since Can use? GCC Apple Clang Comment
std::span C++20 from 1.4 10 11.0.3 Handle buffers like standard library containers without risk of overflow.
std::format C++20 from 1.5 13 15.3 Better and more efficient formatting of strings. Text Formatting
std::lerp C++20 from 1.4 9 11.0.3 Linear interpolation. (ui/tools/pencil-tool.cpp)
std::bit_floor C++20 from 1.4 9/10 11.0.3/13.0.0 Compute floor(log2(x)). (helper/mathfns.h)
Concepts C++20 from 1.5 6/10 12.0.0 Partial Safer templating. (ui/controller.h)
Coroutines C++20 from 1.5 10 10.0.1 Partial,
15.3 Full		 Simpler asynchronous code. (trace/trace.cpp)
std::make_unique_for_overwrite C++20 from 1.5 11 15.0.0 Don't zero arrays allocated using std::make_unique. (util/pool.cpp)
Ranges C++20 from 1.5 ? (ui/dialog/swatches.cpp)
Structural templates C++20 from 1.4? Partial Allow instances of arbitrary literal classes as template parameters. (display/drawing.cpp)
Mathematical Constants C++20 10 12.0.5 Constants like std::numbers::pi.
Heterogenous lookup in std::unordered_map C++20 from 1.5 Faster lookup, use of smart pointers as keys.
consteval static member functions C++20 not yet Guaranteed compile time evaluation of member functions (stronger than constexpr)

References:

As of 21 September 2025, the CI runners for the various supported platforms are

  • Linux: GCC 13.3.0 (on Ubuntu 24.04)
  • Windows: GCC 15.1.0
  • macOS: Apple Clang 17.0.0
  • Android: Clang 19.0.0 (on Ubuntu 24.04)

We support the latest Debian stable and latest Ubuntu LTS.

Distro gcc clang glib glibmm gtk4 gtkmm4
Debian 13 (Trixie) 14.2.0 19.0 2.84.4 2.84.0 4.18.6 4.18.0
Ubuntu 24.04 (Noble) 13.3.0 18.1.3 2.80.0 2.78.1 4.14.2 4.10.1

The build requires glibmm >= 2.78.1 and gtkmm4 >= 4.14, however Inkscape will compile its own gtkmm4 if the system version is too old, so building on Ubuntu 24.04 still works out of the box.

Deprecated items that we still use:

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