diff options
| author | Andreas Buhr <andreas.buhr@qt.io> | 2020-11-17 16:36:02 +0100 |
|---|---|---|
| committer | Qt Cherry-pick Bot <cherrypick_bot@qt-project.org> | 2020-12-03 15:09:12 +0000 |
| commit | 0902ff112e7167d29c00838672497c755c1051b4 (patch) | |
| tree | de314e334db1bd9487aff5ee58208c13b470d75e /src/corelib/doc/src | |
| parent | 2537b5c6c34a360f943fd79327eee7a7ba6c3fc8 (diff) | |
Extend container overview documentation, mention Q_DECLARE_TYPEINFO
The container overview documentation did not mention
Q_DECLARE_TYPEINFO and the related optimizations. This patch
adds a short paragraph about it.
Task-number: QTBUG-86584
Change-Id: I5b0b8ce92a47da5f0398cc413fbf3e07b0921e59
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
(cherry picked from commit d545fbb61b699802e9ae1a3c19f4c4bef724fbda)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
Diffstat (limited to 'src/corelib/doc/src')
| -rw-r--r-- | src/corelib/doc/src/containers.qdoc | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/src/corelib/doc/src/containers.qdoc b/src/corelib/doc/src/containers.qdoc index 84cde51a17..c5b70c2675 100644 --- a/src/corelib/doc/src/containers.qdoc +++ b/src/corelib/doc/src/containers.qdoc @@ -474,6 +474,29 @@ with the expected number of items before you insert the items. The next section discusses this topic in more depth. + \section1 Optimizations for Primitive and Relocatable Types + + Qt containers can use optimized code paths if the stored + elements are relocatable or even primitive. + However, whether types are primitive or relocatable + cannot be detected in all cases. + You can declare your types to be primitive or relocatable + by using the Q_DECLARE_TYPEINFO macro with the Q_PRIMITIVE_TYPE + flag or the Q_RELOCATABLE_TYPE flag. See the documentation + of Q_DECLARE_TYPEINFO for further details and usage examples. + + If you do not use Q_DECLARE_TYPEINFO, + Qt will use + \l {https://en.cppreference.com/w/cpp/types/is_trivial} {std::is_trivial_v<T>} + to indentify primitive + types and it will require both + \l {https://en.cppreference.com/w/cpp/types/is_trivially_copyable} {std::is_trivially_copyable_v<T>} + and + \l {https://en.cppreference.com/w/cpp/types/is_destructible} {std::is_trivially_destructible_v<T>} + to identify relocatable types. + This is always a safe choice, albeit + of maybe suboptimal performance. + \section1 Growth Strategies QList<T>, QString, and QByteArray store their items |