QOpenGLWidget with QPainter coredump

lygstate

I was trying to calling QPainter after OpenGL rendering for tangram-es. and then it's coredump

void GLWidget::paintGL()
{
    QPainter painter;
    painter.begin(this);

    painter.beginNativePainting();

    tangramProcessNetworkQueue();
    double timeNow = currentTime();
    tangramUpdate(map, timeNow - lastTime);
    lastTime = timeNow;

    tangramRender(map);

    painter.endNativePainting();

    painter.setPen(Qt::black);
    painter.drawText(20, 40, QStringLiteral(" paintGL calls / s"));
    painter.end();

    update();

}

The stack trace is:

Program received signal SIGSEGV, Segmentation fault.
0x00007fffe4e24ec0 in ?? () from /usr/lib64/dri/swrast_dri.so


#0  0x00007fffe4e24ec0 in ?? () from /usr/lib64/dri/swrast_dri.so
#1  0x00007fffe4e3af58 in ?? () from /usr/lib64/dri/swrast_dri.so
#2  0x00007fffe4e240ec in ?? () from /usr/lib64/dri/swrast_dri.so
#3  0x00007fffe4e24474 in ?? () from /usr/lib64/dri/swrast_dri.so
#4  0x00007ffff6ba2bfd in ?? () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
#5  0x00007ffff6ba4284 in QOpenGL2PaintEngineEx::drawTextItem(QPointF const&, QTextItem const&) () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
#6  0x00007ffff6b01905 in ?? () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
#7  0x00007ffff6b02380 in QPainter::drawText(QPointF const&, QString const&, int, int) () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
#8  0x000000000040c47d in QPainter::drawText (this=0x7fffffffce50, x=20, y=40, 
    s=...) at ../../../../Qt5.7.0/5.7/gcc_64/include/QtGui/qpainter.h:890
#9  0x0000000000409cd1 in GLWidget::paintGL (this=0x6620b0)
    at ../../opengl/qopenglwidget/glwidget.cpp:346
#10 0x00007ffff70e2a25 in ?? ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#11 0x00007ffff70c2b78 in QWidget::event(QEvent*) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#12 0x00007ffff707d52c in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#13 0x00007ffff7084220 in QApplication::notify(QObject*, QEvent*) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#14 0x00007ffff6091ae0 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
---Type <return> to continue, or q <return> to quit---
    () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
#15 0x00007ffff70bb54a in QWidgetPrivate::sendPaintEvent(QRegion const&) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#16 0x00007ffff70e28c1 in QOpenGLWidget::resizeEvent(QResizeEvent*) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#17 0x00007ffff70c300e in QWidget::event(QEvent*) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#18 0x00007ffff707d52c in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#19 0x00007ffff7084220 in QApplication::notify(QObject*, QEvent*) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#20 0x00007ffff6091ae0 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
    () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
#21 0x00007ffff70bb4d2 in QWidgetPrivate::sendPendingMoveAndResizeEvents(bool, bool) () from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#22 0x00007ffff70bf9a6 in QWidgetPrivate::show_helper() ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#23 0x00007ffff70bf8f0 in QWidgetPrivate::showChildren(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#24 0x00007ffff70bf9c2 in QWidgetPrivate::show_helper() ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#25 0x00007ffff70c2635 in QWidget::setVisible(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
---Type <return> to continue, or q <return> to quit---
#26 0x00007ffff70bf958 in QWidgetPrivate::showChildren(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#27 0x00007ffff70bf9c2 in QWidgetPrivate::show_helper() ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#28 0x00007ffff70c2635 in QWidget::setVisible(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#29 0x00007ffff70bf958 in QWidgetPrivate::showChildren(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#30 0x00007ffff70bf9c2 in QWidgetPrivate::show_helper() ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#31 0x00007ffff70c2635 in QWidget::setVisible(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#32 0x00007ffff70bf958 in QWidgetPrivate::showChildren(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#33 0x00007ffff70bf9c2 in QWidgetPrivate::show_helper() ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#34 0x00007ffff70c2635 in QWidget::setVisible(bool) ()
   from /opt/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#35 0x0000000000407df6 in main (argc=1, argv=0x7fffffffdba8)
    at ../../opengl/qopenglwidget/main.cpp:69

So what's going on after all?

kshegunov

@lygstate said in QOpenGLWidget with QPainter coredump:

QPainter::drawText (this=0x7fffffffce50, x=20, y=40, s=...) at ../../../../Qt5.7.0/5.7/gcc_64/include/QtGui/qpainter.h:890

This this=0x7fffffffce50 looks invalid.

What happens if you run this code instead:

void GLWidget::paintGL()
{
    QPainter painter(this);
    painter.beginNativePainting();

    tangramProcessNetworkQueue();
    double timeNow = currentTime();
    tangramUpdate(map, timeNow - lastTime);
    lastTime = timeNow;

    tangramRender(map);

    painter.endNativePainting();

    update(); //< Do this externaly
}

By the way why do you use a native painting block? It's somewhat unusual.

lygstate

OK, I found the cause, it's because the tangramUpdate doesn't release some buffer