Qt6 application Crash on startup on Linux

[sierdzio]

Check if you can reproduce this with some minimal example - if yes please report it on Qt bug tracker.

There have been important changes to QMetaType and QVariant, that may be the cause of this: https://doc-snapshots.qt.io/qt6-dev/qtcore-changes-qt6.html#the-qvariant-class

[JoeCFD]

@nitingera said in Qt6 application Crash on startup on Linux:

from Qt 4.8.6 to Qt 6.2.

from Qt 4.8.6 to Qt 6.2===> pretty big jump. 5.15.2 might be a better choice.

[nitingera]

@sierdzio It is crashing in setstylesheet function. Maybe some significant changes made to it

[nitingera]

@JoeCFD It is not by choice... More of driven by customer demands so no option :)

[SGaist]

Hi,

The two steps port is not a bad idea. Follow the porting guide from Qt 4 to Qt 5 and then do the small adjustments for Qt 6.

Depending on what you are using you should wait for 6.2 so it's still a good idea to go through 5.15

[nitingera]

@SGaist agreed... but not much time... The application is successfully ported on Windows and MAC but only giving issues in Linux. Crashing in stylesheet functions

[SGaist]

Which version of Qt are you using on Linux ?

Did you try to start from an empty stylesheet and add back elements until it crashes ?

Which version of Linux are you using ?

[nitingera]

Built the Qt6.2 branch on CentOS 7.6

The debug output gives this call stack

1 QMetaType::canConvert qmetatype.cpp 2415 0x7fffee147754
2 QVariant::canConvert qvariant.h 252 0x7fffee1ae916
3 QVariant::convert qvariant.cpp 2054 0x7fffee1ad48c
4 parseColorValue qcssparser.cpp 714 0x7fffefc4c58a
5 parseBrushValue qcssparser.cpp 814 0x7fffefc4d0aa
6 QCss::ValueExtractor::borderValue qcssparser.cpp 1009 0x7fffefc4e808
7 QCss::ValueExtractor::extractBorder qcssparser.cpp 631 0x7fffefc4bebc
8 QRenderRule::QRenderRule qstylesheetstyle.cpp 968 0x7ffff06b7469
9 QStyleSheetStyle::renderRule qstylesheetstyle.cpp 1854 0x7ffff06bc65c
10 QStyleSheetStyle::setGeometry qstylesheetstyle.cpp 2571 0x7ffff06be69f
11 QStyleSheetStyle::polish qstylesheetstyle.cpp 2884 0x7ffff06c08db
12 QWidget::event qwidget.cpp 8759 0x7ffff062d538
13 QApplicationPrivate::notify_helper qapplication.cpp 3396 0x7ffff05af110
14 QApplication::notify qapplication.cpp 3346 0x7ffff05aef18
15 My_Application::notify My_Application.cpp 490 0x7ffff7e46343
16 My_Application::notify My_Application.cpp 64 0x7ffff1bc190e
17 MyApplicationWithExceptionHandling::notify MyApplicationWithExceptionHandling.cpp 66 0x113d179
18 MyApplication::notify My_Application.cpp 301 0x96112a
19 QCoreApplication::notifyInternal2 qcoreapplication.cpp 1061 0x7fffee104944
20 QCoreApplication::sendEvent qcoreapplication.cpp 1469 0x7fffee1052f0
21 QWidget::ensurePolished qwidget.cpp 9907 0x7ffff062f152
22 QWidget::ensurePolished qwidget.cpp 9916 0x7ffff062f1de
23 QWidget::ensurePolished qwidget.cpp 9916 0x7ffff062f1de
24 QWidgetPrivate::setVisible qwidget.cpp 8078 0x7ffff062b91b
25 QWidget::setVisible qwidget.cpp 8052 0x7ffff062b7b2
26 QWidget::show qwidget.cpp 7678 0x7ffff062a5c7
27 QStackedLayout::setCurrentIndex qstackedlayout.cpp 323 0x7ffff060cffa
28 QStackedLayout::insertWidget qstackedlayout.cpp 233 0x7ffff060cc0e
29 QStackedWidget::insertWidget qstackedwidget.cpp 181 0x7ffff089e88d
30 My_LayoutFrame::addTab myulayoutframe.cpp 459 0x7ffff4af0427
31 My_LayoutArea::add mylayoutarea.cpp 94 0x7ffff4ae8a25

[nitingera]

@SGaist Can it be due to missing style plugin on Linux?
As there are style plugins for Mac and Windows (qwindowsvistastyle.dll) in plugin/styles but nothing for Linux.
Maybe any missing dependency while building?

The Config summary states the following

Qt Widgets:
GTK+ ................................... yes
Styles ................................. Fusion Windows

[SGaist]

Sorry, I lost track of this thread.

No as in the case of style sheets there's a dedicated QStyle subclass for it.

Can you reproduce that with a minimal compilable example ?

[A.A.SEZEN]

Although I think that you have cleaned the build directory of your project, I still wanted to go over the topic.

[nitingera]

@SGaist
Although I can't produce a minimal compilable example as of now but I could find atleast one instance where it is crashing
This line crashes
framePoint->setStyleSheet(QString("border: 1px solid lightGray; background-color: rgb(%1, %2, %3 );")).arg(backgroundCol.red()).arg(backgroundCol.green()).arg(backgroundCol.blue());

But this one works fine
framePoint->setStyleSheet(QString("border: 1px; border-color: rgb(211, 211, 211); background-color: rgb(%1, %2, %3 );")).arg(backgroundCol.red()).arg(backgroundCol.green()).arg(backgroundCol.blue());

Maybe some issue with parsing in stylesheet

[nitingera]

@A-A-SEZEN Commenting some specific stylesheet statements works. Rebuilding the project doesn't solve my issue. Is there anything specific that I need to cleanup?

[SGaist]

You may have found a bug.

Can you reproduce that on a dummy widget ?

[nitingera]

Apologies for false alarm....
It was crashing trying to set style sheet to a non existent plugin...
Issue resolved..
Thanks for the help :)