Crash using background fill symbol in Ubuntu

[Kaemer1645]

What is the bug or the crash?

The crash happened when I use QgsTextBackgroundSettings.fillSymbol() python command.

This is the error message:

QGIS died on signal 11[New LWP 59102]
[New LWP 59103]
[New LWP 59104]
[New LWP 59105]
[New LWP 59107]
[New LWP 59109]
[New LWP 59110]
[New LWP 59111]
[New LWP 59112]
[New LWP 59114]
[New LWP 59118]
[New LWP 59121]
[New LWP 59130]
[New LWP 59145]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
0x00007f95accf849f in __GI___wait4 (pid=59159, stat_loc=0x562770e600ec, options=0, usage=0x0) at ../sysdeps/unix/sysv/linux/wait4.c:30
30 ../sysdeps/unix/sysv/linux/wait4.c: No such file or directory.
[Current thread is 1 (Thread 0x7f959991b240 (LWP 59098))]
#0 0x00007f95accf849f in __GI___wait4 (pid=59159, stat_loc=0x562770e600ec, options=0, usage=0x0) at ../sysdeps/unix/sysv/linux/wait4.c:30
sc_ret = -512
sc_cancel_oldtype = 0
#1 0x000056276c4d2a7c in ()
#2 0x00007f95acc50520 in () at /lib/x86_64-linux-gnu/libc.so.6
#3 __pthread_kill_implementation (no_tid=0, signo=11, threadid=140280503317056) at ./nptl/pthread_kill.c:44
tid =
ret = 0
pd = 0x7f959991b240
old_mask = {__val = {140277891095632, 2451, 5415323478377983999, 140278387127280, 513, 24, 94558943120320, 0, 140278352472546, 4, 11, 24, 140280503314720, 0, 140278352472546, 140278351322501}}
ret =
#4 __pthread_kill_internal (signo=11, threadid=140280503317056) at ./nptl/pthread_kill.c:78
#5 __GI___pthread_kill (threadid=140280503317056, signo=signo@entry=11) at ./nptl/pthread_kill.c:89
#6 0x00007f95acc50476 in __GI_raise (sig=11) at ../sysdeps/posix/raise.c:26
ret =
#7 0x00007f95acc50520 in () at /lib/x86_64-linux-gnu/libc.so.6
#8 0x00007f95adb92617 in QgsTextBackgroundSettings::fillSymbol() const () at /lib/libqgis_core.so.3.28.2
#9 0x00007f9514b75547 in () at /usr/lib/python3/dist-packages/qgis/_core.cpython-310-x86_64-linux-gnu.so
#10 0x00007f95193516b8 in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#11 0x00007f951930c1ac in _PyObject_MakeTpCall () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#12 0x00007f95192a1a0c in _PyEval_EvalFrameDefault () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#13 0x00007f95193ec81f in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#14 0x00007f951929feee in _PyEval_EvalFrameDefault () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#15 0x00007f95193ec81f in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#16 0x00007f951929feee in _PyEval_EvalFrameDefault () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#17 0x00007f95193ec81f in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#18 0x00007f951930d618 in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#19 0x00007f95192a19b8 in _PyEval_EvalFrameDefault () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#20 0x00007f95193ec81f in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#21 0x00007f951930d598 in () at /lib/x86_64-linux-gnu/libpython3.10.so.1.0
#22 0x00007f9519131ba0 in () at /usr/lib/python3/dist-packages/PyQt5/QtCore.abi3.so
#23 0x00007f95191355ae in () at /usr/lib/python3/dist-packages/PyQt5/QtCore.abi3.so
#24 0x00007f95af3f64e5 in () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#25 0x00007f95affea696 in QGroupBox::toggled(bool) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#26 0x00007f95affeb43b in QGroupBox::setChecked(bool) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#27 0x00007f95affeb485 in () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#28 0x00007f95affeb720 in QGroupBox::mouseReleaseEvent(QMouseEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#29 0x00007f9518319ae3 in sipQgsCollapsibleGroupBox::mouseReleaseEvent(QMouseEvent*) () at /usr/lib/python3/dist-packages/qgis/_gui.cpython-310-x86_64-linux-gnu.so
#30 0x00007f95afef14ee in QWidget::event(QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#31 0x00007f95affebba9 in QGroupBox::event(QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#32 0x00007f95183196e3 in sipQgsCollapsibleGroupBox::event(QEvent*) () at /usr/lib/python3/dist-packages/qgis/_gui.cpython-310-x86_64-linux-gnu.so
#33 0x00007f95afeae713 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#34 0x00007f95afeb6364 in QApplication::notify(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#35 0x00007f95adbd95a3 in QgsApplication::notify(QObject*, QEvent*) () at /lib/libqgis_core.so.3.28.2
#36 0x00007f95af3bee3a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#37 0x00007f95afeb4e47 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer&, bool, bool) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#38 0x00007f95aff0ad40 in () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#39 0x00007f95aff0dfd5 in () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#40 0x00007f95afeae713 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#41 0x00007f95adbd95a3 in QgsApplication::notify(QObject*, QEvent*) () at /lib/libqgis_core.so.3.28.2
#42 0x00007f95af3bee3a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#43 0x00007f95af7a5307 in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) () at /lib/x86_64-linux-gnu/libQt5Gui.so.5
#44 0x00007f95af77aa2c in QWindowSystemInterface::sendWindowSystemEvents(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Gui.so.5
#45 0x00007f958fef5d6e in () at /lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#46 0x00007f95a5310d3b in g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#47 0x00007f95a53656c8 in () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#48 0x00007f95a530e3e3 in g_main_context_iteration () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#49 0x00007f95af4180b8 in QEventDispatcherGlib::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#50 0x00007f95af3bd75b in QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#51 0x00007f95af3c5cf4 in QCoreApplication::exec() () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#52 0x000056276c4cf2df in ()
#53 0x00007f95acc37d90 in __libc_start_call_main (main=main@entry=0x56276c4cc960, argc=argc@entry=1, argv=argv@entry=0x7fffc0bdc268) at ../sysdeps/nptl/libc_start_call_main.h:58
self =
result =
unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, -3688092470276969511, 140736427049576, 94727320684896, 94727321027064, 140280919650368, 3688098500729056217, 3745335686942895065}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x56276c521008, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 1817317384}}}
not_first_call =
#54 0x00007f95acc37e40 in __libc_start_main_impl (main=0x56276c4cc960, argc=1, argv=0x7fffc0bdc268, init=, fini=, rtld_fini=, stack_end=0x7fffc0bdc258) at ../csu/libc-start.c:392
#55 0x000056276c4d1c85 in ()
[Inferior 1 (process 59098) detached]
gdb returned 0
Aborted (core dumped)

Steps to reproduce the issue

Use this code.

lyr = iface.activeLayer()
labeling = lyr.labeling()
settings = labeling.settings()
background = settings.format().background()
symbols = background.fillSymbol().symbolLayers()

Versions

Ubuntu 22.04.1 LTS jammy

QGIS version
3.28.2-Firenze
QGIS code revision
b47e00b
Qt version
5.15.3
Python version
3.10.6
GDAL/OGR version
3.4.1
PROJ version
8.2.1
EPSG Registry database version
v10.041 (2021-12-03)
GEOS version
3.10.2-CAPI-1.16.0
SQLite version
3.37.2
PDAL version
2.3.0
PostgreSQL client version
unknown
SpatiaLite version
5.0.1
QWT version
6.1.4
QScintilla2 version
2.11.6
OS version
Ubuntu 22.04.1 LTS

Active Python plugins
QMapa
2.0.0
plugin_reloader
0.9.2
sagaprovider
2.12.99
db_manager
0.1.20
MetaSearch
0.3.6
processing
2.12.99
grassprovider
2.12.99

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

I tried to check this issue using Ubuntu 22.10 kinetic and I got the same error.

[nicogodet]

Confirmed on Windows too

[nyalldawson]

Change your code to something like this:

text_format = settings.format()
background = text_format.background()
background_fill_symbol = background.fillSymbol()
symbols = background_fill_symbol.symbolLayers()

The Python garbage collector is cleaning up the underlying c++ objects too aggressively -- if you store them in variables then you can prevent this.