Switch to C++20

PR #19336.

cmake/Modules/CommonConfig.cmake

@@ -12,11 +12,11 @@ set(CMAKE_AUTORCC_OPTIONS --compress 9 --threshold 5)
 
 add_library(qbt_common_cfg INTERFACE)
 
-# Full C++ 17 support is required
+# Full C++ 20 support is required
 # See also https://cmake.org/cmake/help/latest/prop_gbl/CMAKE_CXX_KNOWN_FEATURES.html
 # for a breakdown of the features that CMake recognizes for each C++ standard
 target_compile_features(qbt_common_cfg INTERFACE
-    cxx_std_17
+    cxx_std_20
 )
 
 target_compile_definitions(qbt_common_cfg INTERFACE

src/app/application.cpp

@@ -464,8 +464,7 @@ void Application::processMessage(const QString &message)
 #ifndef DISABLE_GUI
     if (message.isEmpty())
     {
-        // TODO: use [[likely]] in C++20
-        if (Q_LIKELY(BitTorrent::Session::instance()->isRestored()))
+        if (BitTorrent::Session::instance()->isRestored()) [[likely]]
         {
             m_window->activate(); // show UI
         }

src/base/bittorrent/customstorage.cpp

@@ -118,7 +118,7 @@ void CustomDiskIOThread::async_move_storage(lt::storage_index_t storage, std::st
         handleCompleteFiles(storage, newSavePath);
 
     m_nativeDiskIO->async_move_storage(storage, path, flags
-                                       , [=, handler = std::move(handler)](lt::status_t status, const std::string &path, const lt::storage_error &error)
+            , [=, this, handler = std::move(handler)](lt::status_t status, const std::string &path, const lt::storage_error &error)
     {
 #if LIBTORRENT_VERSION_NUM < 20100
         if ((status != lt::status_t::fatal_disk_error) && (status != lt::status_t::file_exist))
@@ -153,7 +153,7 @@ void CustomDiskIOThread::async_rename_file(lt::storage_index_t storage, lt::file
                                            , std::function<void (const std::string &, lt::file_index_t, const lt::storage_error &)> handler)
 {
     m_nativeDiskIO->async_rename_file(storage, index, name
-                                      , [=, handler = std::move(handler)](const std::string &name, lt::file_index_t index, const lt::storage_error &error)
+            , [=, this, handler = std::move(handler)](const std::string &name, lt::file_index_t index, const lt::storage_error &error)
     {
         if (!error)
             m_storageData[storage].files.rename_file(index, name);
@@ -171,7 +171,7 @@ void CustomDiskIOThread::async_set_file_priority(lt::storage_index_t storage, lt
                                                  , std::function<void (const lt::storage_error &, lt::aux::vector<lt::download_priority_t, lt::file_index_t>)> handler)
 {
     m_nativeDiskIO->async_set_file_priority(storage, std::move(priorities)
-                                            , [=, handler = std::move(handler)](const lt::storage_error &error, const lt::aux::vector<lt::download_priority_t, lt::file_index_t> &priorities)
+            , [=, this, handler = std::move(handler)](const lt::storage_error &error, const lt::aux::vector<lt::download_priority_t, lt::file_index_t> &priorities)
     {
         m_storageData[storage].filePriorities = priorities;
         handler(error, priorities);

src/base/bittorrent/sessionimpl.cpp

@@ -2904,7 +2904,7 @@ void SessionImpl::findIncompleteFiles(const TorrentInfo &torrentInfo, const Path
 
     const auto searchId = TorrentID::fromInfoHash(torrentInfo.infoHash());
     const PathList originalFileNames = (filePaths.isEmpty() ? torrentInfo.filePaths() : filePaths);
-    QMetaObject::invokeMethod(m_fileSearcher, [=]()
+    QMetaObject::invokeMethod(m_fileSearcher, [=, this]
     {
         m_fileSearcher->search(searchId, originalFileNames, savePath, downloadPath, isAppendExtensionEnabled());
     });

src/base/bittorrent/torrentimpl.cpp

@@ -1217,7 +1217,7 @@ QVector<qreal> TorrentImpl::filesProgress() const
 
     const int count = m_filesProgress.size();
     Q_ASSERT(count == filesCount());
-    if (Q_UNLIKELY(count != filesCount()))
+    if (count != filesCount()) [[unlikely]]
         return {};
 
     if (m_completedFiles.count(true) == count)
@@ -1613,8 +1613,7 @@ TrackerEntry TorrentImpl::updateTrackerEntry(const lt::announce_entry &announceE
     });
 
     Q_ASSERT(it != m_trackerEntries.end());
-    // TODO: use [[unlikely]] in C++20
-    if (Q_UNLIKELY(it == m_trackerEntries.end()))
+    if (it == m_trackerEntries.end()) [[unlikely]]
         return {};
 
 #ifdef QBT_USES_LIBTORRENT2
@@ -1813,7 +1812,7 @@ void TorrentImpl::moveStorage(const Path &newPath, const MoveStorageContext cont
 void TorrentImpl::renameFile(const int index, const Path &path)
 {
     Q_ASSERT((index >= 0) && (index < filesCount()));
-    if (Q_UNLIKELY((index < 0) || (index >= filesCount())))
+    if ((index < 0) || (index >= filesCount())) [[unlikely]]
         return;
 
     const Path wantedPath = wantedActualPath(index, path);
@@ -2276,7 +2275,7 @@ void TorrentImpl::doRenameFile(int index, const Path &path)
 
     Q_ASSERT(index >= 0);
     Q_ASSERT(index < nativeIndexes.size());
-    if (Q_UNLIKELY((index < 0) || (index >= nativeIndexes.size())))
+    if ((index < 0) || (index >= nativeIndexes.size())) [[unlikely]]
         return;
 
     ++m_renameCount;
@@ -2364,11 +2363,11 @@ void TorrentImpl::updateStatus(const lt::torrent_status &nativeStatus)
 void TorrentImpl::updateProgress()
 {
     Q_ASSERT(hasMetadata());
-    if (Q_UNLIKELY(!hasMetadata()))
+    if (!hasMetadata()) [[unlikely]]
         return;
 
     Q_ASSERT(!m_filesProgress.isEmpty());
-    if (Q_UNLIKELY(m_filesProgress.isEmpty()))
+    if (m_filesProgress.isEmpty()) [[unlikely]]
         m_filesProgress.resize(filesCount());
 
     const QBitArray oldPieces = std::exchange(m_pieces, LT::toQBitArray(m_nativeStatus.pieces));

src/base/http/connection.cpp

@@ -74,12 +74,12 @@ void Connection::read()
     const qint64 bytesAvailable = m_socket->bytesAvailable();
     m_receivedData.resize(previousSize + bytesAvailable);
     const qint64 bytesRead = m_socket->read((m_receivedData.data() + previousSize), bytesAvailable);
-    if (Q_UNLIKELY(bytesRead < 0))
+    if (bytesRead < 0) [[unlikely]]
     {
         m_socket->close();
         return;
     }
-    if (Q_UNLIKELY(bytesRead < bytesAvailable))
+    if (bytesRead < bytesAvailable) [[unlikely]]
         m_receivedData.chop(bytesAvailable - bytesRead);
 
     while (!m_receivedData.isEmpty())

src/base/orderedset.h

@@ -51,13 +51,6 @@ public:
 
     // The following are custom functions that are in line with Qt API interface, such as `QSet`
 
-#if __cplusplus < 202002L
-    bool contains(const key_type &value) const
-    {
-        return (BaseType::find(value) != BaseType::cend());
-    }
-#endif
-
     int count() const
     {
         return static_cast<int>(BaseType::size());

src/base/rss/rss_feed.cpp

@@ -524,8 +524,7 @@ void Feed::handleArticleLoadFinished(QVector<QVariantHash> articles)
     for (const QVariantHash &articleData : articles)
     {
         const auto articleID = articleData.value(Article::KeyId).toString();
-        // TODO: use [[unlikely]] in C++20
-        if (Q_UNLIKELY(m_articles.contains(articleID)))
+        if (m_articles.contains(articleID)) [[unlikely]]
             continue;
 
         auto *article = new Article(this, articleData);

src/gui/addnewtorrentdialog.cpp

@@ -898,7 +898,7 @@ void AddNewTorrentDialog::setMetadataProgressIndicator(bool visibleIndicator, co
 void AddNewTorrentDialog::setupTreeview()
 {
     Q_ASSERT(hasMetadata());
-    if (Q_UNLIKELY(!hasMetadata()))
+    if (!hasMetadata()) [[unlikely]]
         return;
 
     // Set dialog title

src/gui/rss/rsswidget.cpp

@@ -434,7 +434,7 @@ void RSSWidget::editSelectedRSSFeedURL()
     QTreeWidgetItem *item = selectedItems.first();
     RSS::Feed *rssFeed = qobject_cast<RSS::Feed *>(m_feedListWidget->getRSSItem(item));
     Q_ASSERT(rssFeed);
-    if (Q_UNLIKELY(!rssFeed))
+    if (!rssFeed) [[unlikely]]
         return;
 
     bool ok = false;

src/gui/torrentcontentmodel.cpp

@@ -212,7 +212,7 @@ void TorrentContentModel::updateFilesProgress()
     const QVector<qreal> &filesProgress = m_contentHandler->filesProgress();
     Q_ASSERT(m_filesIndex.size() == filesProgress.size());
     // XXX: Why is this necessary?
-    if (Q_UNLIKELY(m_filesIndex.size() != filesProgress.size()))
+    if (m_filesIndex.size() != filesProgress.size()) [[unlikely]]
         return;
 
     for (int i = 0; i < filesProgress.size(); ++i)
@@ -248,7 +248,7 @@ void TorrentContentModel::updateFilesAvailability()
 
         Q_ASSERT(m_filesIndex.size() == availableFileFractions.size());
         // XXX: Why is this necessary?
-        if (Q_UNLIKELY(m_filesIndex.size() != availableFileFractions.size()))
+        if (m_filesIndex.size() != availableFileFractions.size()) [[unlikely]]
             return;
 
         for (int i = 0; i < m_filesIndex.size(); ++i)

src/gui/torrentcontentwidget.cpp

@@ -454,7 +454,7 @@ void TorrentContentWidget::onItemDoubleClicked(const QModelIndex &index)
     const auto *contentHandler = m_model->contentHandler();
     Q_ASSERT(contentHandler && contentHandler->hasMetadata());
 
-    if (Q_UNLIKELY(!contentHandler || !contentHandler->hasMetadata()))
+    if (!contentHandler || !contentHandler->hasMetadata()) [[unlikely]]
         return;
 
     if (m_doubleClickAction == DoubleClickAction::Rename)

src/gui/transferlistfilters/trackersfilterwidget.cpp

@@ -392,7 +392,7 @@ void TrackersFilterWidget::handleFavicoDownloadFinished(const Net::DownloadResul
 {
     const QSet<QString> trackerHosts = m_downloadingFavicons.take(result.url);
     Q_ASSERT(!trackerHosts.isEmpty());
-    if (Q_UNLIKELY(trackerHosts.isEmpty()))
+    if (trackerHosts.isEmpty()) [[unlikely]]
         return;
 
     QIcon icon;
@@ -439,7 +439,7 @@ void TrackersFilterWidget::handleFavicoDownloadFinished(const Net::DownloadResul
 
         QListWidgetItem *trackerItem = item(rowFromTracker(trackerHost));
         Q_ASSERT(trackerItem);
-        if (Q_UNLIKELY(!trackerItem))
+        if (!trackerItem) [[unlikely]]
             continue;
 
         trackerItem->setData(Qt::DecorationRole, icon);

src/webui/api/synccontroller.cpp

@@ -880,7 +880,7 @@ void SyncController::onTorrentAboutToBeRemoved(BitTorrent::Torrent *torrent)
     {
         auto iter = m_knownTrackers.find(trackerEntry.url);
         Q_ASSERT(iter != m_knownTrackers.end());
-        if (Q_UNLIKELY(iter == m_knownTrackers.end()))
+        if (iter == m_knownTrackers.end()) [[unlikely]]
             continue;
 
         QSet<BitTorrent::TorrentID> &torrentIDs = iter.value();

test/testorderedset.cpp

@@ -42,20 +42,6 @@ public:
     TestOrderedSet() = default;
 
 private slots:
-#if __cplusplus < 202002L
-    void testContains() const
-    {
-        const OrderedSet<QString> set {u"a"_s, u"b"_s, u"c"_s};
-        QVERIFY(set.contains(u"a"_s));
-        QVERIFY(set.contains(u"b"_s));
-        QVERIFY(set.contains(u"c"_s));
-        QVERIFY(!set.contains(u"z"_s));
-
-        const OrderedSet<QString> emptySet;
-        QVERIFY(!emptySet.contains(u"a"_s));
-    }
-#endif
-
     void testCount() const
     {
         const OrderedSet<QString> set {u"a"_s, u"b"_s, u"c"_s, u"c"_s};