How do I delete the current QTreeWidget element correctly?

VRonin

@Helg1980
Start the debugger. If you have a debugger in the background it will tell you where the assertion occurred.

Q_ASSERT and Q_ASSUME are used to test implicit assumptions you make in your code.

Looking at the sources QTreeWidget it looked like item->parent() for a top level item would return the invisible root item. I tested this implicit assumption with Q_ASSERT and it turns out I was wrong (but at least we know why)

void SelectPreset::on_actionRemove_preset_clicked()  // Remove preset
{
    QTreeWidgetItem *item = ui_selectpreset->treeWidget->currentItem();
    if(!item)
        return;
    QTreeWidgetItem *parentItem = item->parent();
    QTreeWidgetItem *takenItem = nullptr;
    if(parentItem)
        takenItem  = parentItem->takeChild(parentItem->indexOfChild(item));
    else
        takenItem  = ui_selectpreset->treeWidget->takeTopLevelItem(ui_selectpreset->treeWidget->indexOfTopLevelItem(item));
    Q_ASSERT(takenItem==item);
    delete takenItem;
}

Helg1980

Finally, I finished the program and ran it through 'valgrind'. The result was disappointing:

valgrind --leak-check=full --leak-resolution=med /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/build-cine_encoder-Desktop-Debug/cine_encoder
.
.
.
==2615== HEAP SUMMARY:
==2615==     in use at exit: 568,907 bytes in 7,703 blocks
==2615==   total heap usage: 880,287 allocs, 872,584 frees, 5,593,630,039 bytes allocated
==2615== 
==2615== 24 bytes in 1 blocks are definitely lost in loss record 89 of 557
==2615==    at 0x483A77F: malloc (vg_replace_malloc.c:307)
==2615==    by 0xDE61E5E: XextCreateExtension (in /usr/lib/libXext.so.6.4.0)
==2615==    by 0x1074014B: ???
==2615==    by 0x1073775C: ???
==2615==    by 0x10662091: ??? (in /usr/lib/qt/plugins/xcbglintegrations/libqxcb-glx-integration.so)
==2615==    by 0xA28C084: QXcbWindow::create() (in /usr/lib/libQt5XcbQpa.so.5.15.1)
==2615==    by 0xA27A746: QXcbIntegration::createPlatformWindow(QWindow*) const (in /usr/lib/libQt5XcbQpa.so.5.15.1)
==2615==    by 0x5842F26: QWindowPrivate::create(bool, unsigned long long) (in /usr/lib/libQt5Gui.so.5.15.1)
==2615==    by 0x51F78A7: QWidgetPrivate::create() (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x51F7E20: QWidget::create(unsigned long long, bool, bool) (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x520551B: QWidgetPrivate::setVisible(bool) (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x117E3F: main (main.cpp:10)
==2615== 
==2615== 96 (64 direct, 32 indirect) bytes in 1 blocks are definitely lost in loss record 316 of 557
==2615==    at 0x483ADEF: operator new(unsigned long) (vg_replace_malloc.c:342)
==2615==    by 0x159CCB: SelectPreset::SelectPreset(QWidget*) (selectpreset.cpp:28)
==2615==    by 0x129258: MainWindow::on_actionPreset_clicked() (mainwindow.cpp:1279)
==2615==    by 0x1659B3: MainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (moc_mainwindow.cpp:156)
==2615==    by 0x165B5F: MainWindow::qt_metacall(QMetaObject::Call, int, void**) (moc_mainwindow.cpp:204)
==2615==    by 0x60B5D71: ??? (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x52B5B22: QAbstractButton::clicked(bool) (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x52B64AB: ??? (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x52B7E52: ??? (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x52B8032: QAbstractButton::mouseReleaseEvent(QMouseEvent*) (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x5205B0D: QWidget::event(QEvent*) (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615==    by 0x51C4751: QApplicationPrivate::notify_helper(QObject*, QEvent*) (in /usr/lib/libQt5Widgets.so.5.15.1)
==2615== 
==2615== 160 bytes in 1 blocks are possibly lost in loss record 369 of 557
==2615==    at 0x483A77F: malloc (vg_replace_malloc.c:307)
==2615==    by 0x60A8595: QObjectPrivate::addConnection(int, QObjectPrivate::Connection*) (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x60AC9DE: QObjectPrivate::connectImpl(QObject const*, int, QObject const*, void**, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, int const*, QMetaObject const*) (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x60ACEB5: QObject::connectImpl(QObject const*, void**, QObject const*, void**, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, int const*, QMetaObject const*) (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0xA3D1BBD: QDBusConnectionInterface::QDBusConnectionInterface(QDBusConnection const&, QObject*) (in /usr/lib/libQt5DBus.so.5.15.1)
==2615==    by 0xA3CEB3A: ??? (in /usr/lib/libQt5DBus.so.5.15.1)
==2615==    by 0xA3CFD13: ??? (in /usr/lib/libQt5DBus.so.5.15.1)
==2615==    by 0x60AB7E1: QObject::event(QEvent*) (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x607ECAF: QCoreApplication::notifyInternal2(QObject*, QEvent*) (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x60817D2: QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x60D8303: ??? (in /usr/lib/libQt5Core.so.5.15.1)
==2615==    by 0x6A2CBFB: g_main_context_dispatch (in /usr/lib/libglib-2.0.so.0.6600.0)
==2615== 
==2615== 302 (256 direct, 46 indirect) bytes in 1 blocks are definitely lost in loss record 409 of 557
==2615==    at 0x483A77F: malloc (vg_replace_malloc.c:307)
==2615==    by 0xA38F9E2: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615==    by 0xA3902E4: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615==    by 0xA391BEB: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615==    by 0xA399E59: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615==    by 0xA5309E7: ??? (in /usr/lib/libexpat.so.1.6.11)
==2615==    by 0xA52EDDC: ??? (in /usr/lib/libexpat.so.1.6.11)
==2615==    by 0xA532620: ??? (in /usr/lib/libexpat.so.1.6.11)
==2615==    by 0xA5348CB: XML_ParseBuffer (in /usr/lib/libexpat.so.1.6.11)
==2615==    by 0xA397024: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615==    by 0xA397657: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615==    by 0xA397713: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==2615== 
==2615== LEAK SUMMARY:
==2615==    definitely lost: 344 bytes in 3 blocks
==2615==    indirectly lost: 78 bytes in 3 blocks
==2615==      possibly lost: 160 bytes in 1 blocks
==2615==    still reachable: 568,305 bytes in 7,694 blocks
==2615==                       of which reachable via heuristic:
==2615==                         newarray           : 4,264 bytes in 1 blocks
==2615==         suppressed: 20 bytes in 2 blocks
==2615== Reachable blocks (those to which a pointer was found) are not shown.
==2615== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==2615== 
==2615== Use --track-origins=yes to see where uninitialised values come from
==2615== For lists of detected and suppressed errors, rerun with: -s
==2615== ERROR SUMMARY: 107 errors from 107 contexts (suppressed: 0 from 0)

Christian Ehrlicher

@Helg1980 said in How do I delete the current QTreeWidget element correctly?:

The result was disappointing:

Why? There is only one leak which should interest you:

==2615== by 0x159CCB: SelectPreset::SelectPreset(QWidget*) (selectpreset.cpp:28)

The rest are no real 'leaks' and can be ignored.

Helg1980

Here is a part of the text where there may be an error:

SelectPreset::SelectPreset(QWidget *parent) :
    QDialog(parent),
    ui_selectpreset(new Ui::SelectPreset)
{
    ui_selectpreset->setupUi(this);
    ui_selectpreset->treeWidget->clear();
    int n =  _preset_table[0].size();
    int m = _preset_table.size();
    QString type;
    QColor color;
    color.setRgba(qRgb(120, 120, 150));
    QFont font;
    font.setBold(true);
    QTreeWidgetItem *item = new QTreeWidgetItem();    //    line 28  -  deleted this line
    for (int i = 0; i < n; i++) {
        type = _preset_table[23][i];
        if (type == "TopLewelItem") {
            QTreeWidgetItem *root = new QTreeWidgetItem();
            root->setText(0, _preset_table[0][i]);
            ui_selectpreset->treeWidget->addTopLevelItem(root);
            ui_selectpreset->treeWidget->setCurrentItem(root);
            root->setFlags(Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsEditable);
            root->setFont(0, font);
            root->setForeground(0, color);
        };
        if (type == "ChildItem") {
            item = ui_selectpreset->treeWidget->currentItem();   // replaced with: QTreeWidgetItem *item =  ....
            QTreeWidgetItem *child = new QTreeWidgetItem();
            for (int j = 0; j < 23; j++) {
                child->setText(j, _preset_table[j][i]);
            };
            child->setFlags(Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsEditable);
            item->addChild(child);
        };
    };
    item = ui_selectpreset->treeWidget->topLevelItem(pos_top)->child(pos_cld);   // replaced with: QTreeWidgetItem *item =  ....
    ui_selectpreset->treeWidget->setCurrentItem(item);
    std::cout << n << " x " << m << std::endl; // Table size
    ui_selectpreset->treeWidget->expandAll();
    for (int i=1; i<=24; i++) {
        ui_selectpreset->treeWidget->hideColumn(i);
    };
    QAction *addsection = new QAction(tr("Add section"), this);
    QAction *addpreset = new QAction(tr("Add new preset"), this);
    connect(addsection, &QAction::triggered, this, &SelectPreset::add_section);
    connect(addpreset, &QAction::triggered, this, &SelectPreset::add_preset);
    QMenu* menu = new QMenu(this);
    menu->addAction(addsection);
    menu->addAction(addpreset);
    menu->setStyleSheet("QMenu {background-color: rgb(5, 20, 25);} "
                        "QMenu::item {background-color: transparent;} "
                        "QMenu::item:selected {background-color: rgb(5, 40, 45);}");
    ui_selectpreset->actionAdd_preset->setMenu(menu);
}

JonB

@Helg1980 said in How do I delete the current QTreeWidget element correctly?:

QTreeWidgetItem *item = new QTreeWidgetItem(); // line 28

So, as the valgrind tells you, in all cases you do not use/overwrite this newed item without using it. Hence the leak.

Helg1980

This post is deleted!

JonB

@Helg1980
So I see. So now has that leak gone away? That's all you are looking to resolve.

Helg1980

It looks like the error has disappeared. I don't work very well with valgrind yet. So I understand that I only need to search for lines where there are links to my files.

==7099== HEAP SUMMARY:
==7099==     in use at exit: 571,790 bytes in 7,682 blocks
==7099==   total heap usage: 833,977 allocs, 826,295 frees, 5,575,110,174 bytes allocated
==7099== 
==7099== 24 bytes in 1 blocks are definitely lost in loss record 94 of 561
==7099==    at 0x483A77F: malloc (vg_replace_malloc.c:307)
==7099==    by 0xDE61E5E: XextCreateExtension (in /usr/lib/libXext.so.6.4.0)
==7099==    by 0x1074014B: ???
==7099==    by 0x1073775C: ???
==7099==    by 0x10662091: ??? (in /usr/lib/qt/plugins/xcbglintegrations/libqxcb-glx-integration.so)
==7099==    by 0xA28C084: QXcbWindow::create() (in /usr/lib/libQt5XcbQpa.so.5.15.1)
==7099==    by 0xA27A746: QXcbIntegration::createPlatformWindow(QWindow*) const (in /usr/lib/libQt5XcbQpa.so.5.15.1)
==7099==    by 0x5842F26: QWindowPrivate::create(bool, unsigned long long) (in /usr/lib/libQt5Gui.so.5.15.1)
==7099==    by 0x51F78A7: QWidgetPrivate::create() (in /usr/lib/libQt5Widgets.so.5.15.1)
==7099==    by 0x51F7E20: QWidget::create(unsigned long long, bool, bool) (in /usr/lib/libQt5Widgets.so.5.15.1)
==7099==    by 0x520551B: QWidgetPrivate::setVisible(bool) (in /usr/lib/libQt5Widgets.so.5.15.1)
==7099==    by 0x117E3F: main (main.cpp:10)
==7099== 
==7099== 160 bytes in 1 blocks are possibly lost in loss record 372 of 561
==7099==    at 0x483A77F: malloc (vg_replace_malloc.c:307)
==7099==    by 0x60A8595: QObjectPrivate::addConnection(int, QObjectPrivate::Connection*) (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0x60AC9DE: QObjectPrivate::connectImpl(QObject const*, int, QObject const*, void**, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, int const*, QMetaObject const*) (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0x60ACEB5: QObject::connectImpl(QObject const*, void**, QObject const*, void**, QtPrivate::QSlotObjectBase*, Qt::ConnectionType, int const*, QMetaObject const*) (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0xA3D1BBD: QDBusConnectionInterface::QDBusConnectionInterface(QDBusConnection const&, QObject*) (in /usr/lib/libQt5DBus.so.5.15.1)
==7099==    by 0xA3CEB3A: ??? (in /usr/lib/libQt5DBus.so.5.15.1)
==7099==    by 0xA3CFD13: ??? (in /usr/lib/libQt5DBus.so.5.15.1)
==7099==    by 0x60AB7E1: QObject::event(QEvent*) (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0x607ECAF: QCoreApplication::notifyInternal2(QObject*, QEvent*) (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0x60817D2: QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0x60D8303: ??? (in /usr/lib/libQt5Core.so.5.15.1)
==7099==    by 0x6A2CBFB: g_main_context_dispatch (in /usr/lib/libglib-2.0.so.0.6600.0)
==7099== 
==7099== 302 (256 direct, 46 indirect) bytes in 1 blocks are definitely lost in loss record 414 of 561
==7099==    at 0x483A77F: malloc (vg_replace_malloc.c:307)
==7099==    by 0xA38F9E2: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099==    by 0xA3902E4: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099==    by 0xA391BEB: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099==    by 0xA399E59: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099==    by 0xA5309E7: ??? (in /usr/lib/libexpat.so.1.6.11)
==7099==    by 0xA52EDDC: ??? (in /usr/lib/libexpat.so.1.6.11)
==7099==    by 0xA532620: ??? (in /usr/lib/libexpat.so.1.6.11)
==7099==    by 0xA5348CB: XML_ParseBuffer (in /usr/lib/libexpat.so.1.6.11)
==7099==    by 0xA397024: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099==    by 0xA397657: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099==    by 0xA397713: ??? (in /usr/lib/libfontconfig.so.1.12.0)
==7099== 
==7099== LEAK SUMMARY:
==7099==    definitely lost: 280 bytes in 2 blocks
==7099==    indirectly lost: 46 bytes in 2 blocks
==7099==      possibly lost: 160 bytes in 1 blocks
==7099==    still reachable: 571,284 bytes in 7,675 blocks
==7099==                       of which reachable via heuristic:
==7099==                         newarray           : 4,264 bytes in 1 blocks
==7099==         suppressed: 20 bytes in 2 blocks
==7099== Reachable blocks (those to which a pointer was found) are not shown.
==7099== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==7099== 
==7099== Use --track-origins=yes to see where uninitialised values come from
==7099== For lists of detected and suppressed errors, rerun with: -s
==7099== ERROR SUMMARY: 80 errors from 80 contexts (suppressed: 0 from 0)

JonB

@Helg1980
Are you running valgrind yourself with those command-line arguments? I run it from inside Qt Creator, from the menu item. I (Ubuntu 20.04) always get exactly 32 leaks, which with the default of the checkbox which says something about "don't report system ones" being checked, are always suppressed, so I don't see them. Any genuine ones from my own code are then the only ones reported.

Helg1980

This post is deleted!

Helg1980

Here's what valgrind QtCreator gives me. There are 35 errors in total.

160 bytes in 1 blocks are possibly lost in loss record 6,742 of 8,837
  in Ui_MainWindow::setupUi(QMainWindow*) in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/build-cine_encoder-Desktop-Debug/ui_mainwindow.h:556
  1: malloc in /build/valgrind/src/valgrind-3.16.1/coregrind/m_replacemalloc/vg_replace_malloc.c:307
  2: QObjectPrivate::addConnection(int, QObjectPrivate::Connection*) in /usr/lib/libQt5Core.so.5.15.1
  3: /usr/lib/libQt5Core.so.5.15.1
  4: QObject::connect(QObject const*, char const*, QObject const*, char const*, Qt::ConnectionType) in /usr/lib/libQt5Core.so.5.15.1
  5: /usr/lib/libQt5Widgets.so.5.15.1
  6: Ui_MainWindow::setupUi(QMainWindow*) in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/build-cine_encoder-Desktop-Debug/ui_mainwindow.h:556
  7: MainWindow::MainWindow(QWidget*) in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/cine-encoder-3.0/app/mainwindow.cpp:71
  8: main in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/cine-encoder-3.0/app/main.cpp:9
288 bytes in 1 blocks are possibly lost in loss record 7,317 of 8,837
  in Ui_MainWindow::setupUi(QMainWindow*) in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/build-cine_encoder-Desktop-Debug/ui_mainwindow.h:556
  1: malloc in /build/valgrind/src/valgrind-3.16.1/coregrind/m_replacemalloc/vg_replace_malloc.c:307
  2: QObjectPrivate::addConnection(int, QObjectPrivate::Connection*) in /usr/lib/libQt5Core.so.5.15.1
  3: /usr/lib/libQt5Core.so.5.15.1
  4: QObject::connect(QObject const*, char const*, QObject const*, char const*, Qt::ConnectionType) in /usr/lib/libQt5Core.so.5.15.1
  5: /usr/lib/libQt5Widgets.so.5.15.1
  6: Ui_MainWindow::setupUi(QMainWindow*) in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/build-cine_encoder-Desktop-Debug/ui_mainwindow.h:556
  7: MainWindow::MainWindow(QWidget*) in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/cine-encoder-3.0/app/mainwindow.cpp:71
  8: main in /run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/cine-encoder-3.0/app/main.cpp:9

VRonin

All looks good to me, only false positives left

Helg1980

Thanks!

I'm still confused by these lines, I don't know what to do with it:

QCssParser::parseColorValue: Specified color without alpha value but alpha given: 'rgb 27, 29, 35, 0'
QCssParser::parseColorValue: Specified color without alpha value but alpha given: 'rgb 27, 29, 35, 0'
kf.kio.core: We got some errors while running testparm "Error loading services."
kf.kio.core: We got some errors while running 'net usershare info'
kf.kio.core: "Can't load /etc/samba/smb.conf - run testparm to debug it\n"
kf.kio.widgets.kdirmodel: No node found for item that was just removed: QUrl("file:///run/media/helg/GOODRAM-SDB/QtCreatorProjects/CineEncoder/build-cine_encoder-Desktop-Debug/Makefile")

Christian Ehrlicher

@Helg1980 said in How do I delete the current QTreeWidget element correctly?:

QCssParser::parseColorValue: Specified color without alpha value but alpha given: 'rgb 27, 29, 35, 0'

You have a css somewhere which defines a wrong color rgb value.