Problems with Qt?

LudwigJ · Today 15:20:29

I haven't found anyone complaining about this, but after a system update today, several applications are crashing, apparently due to problems with qt.

- Telegram fails thus:

QPainter::begin: Paint device returned engine == 0, type: 2
QWidget::render: Cannot render with an inactive painter
Segmentation fault (core dumped) Telegram

- ebook-viewer fails thus:

[3:3:0100/000000.908457:ERROR:../../../qtwebengine/src/3rdparty/chromium/content/zygote/zygote_linux.cc:621] Zygote could not fork: process_type renderer numfds 5 child_pid -1
[3:3:0100/000000.908513:ERROR:../../../qtwebengine/src/3rdparty/chromium/content/zygote/zygote_linux.cc:653] write: Broken pipe (32)
Segmentation fault (core dumped) ebook-viewer

- qbittorrent is more verbose:

qBittorrent version: v5.2.1

Caught signal: SIGSEGV
```
0# getStacktrace[abi:cxx11]() in qbittorrent
1# 0x00000000001F1364 in qbittorrent
2# 0x000000000003E8F0 in /usr/lib/libc.so.6
3# 0x000000000000E9AC in /usr/lib/libfontconfig.so.1
4# FcCharSetHasChar in /usr/lib/libfontconfig.so.1
5# QFontEngineMulti::stringToCMap(QChar const*, int, QGlyphLayout*, int*, QFlags<QFontEngine::ShaperFlag>) const in /usr/lib/libQt6Gui.so.6
6# QTextEngine::shapeText(int) const in /usr/lib/libQt6Gui.so.6
7# QTextLine::layout_helper(int) in /usr/lib/libQt6Gui.so.6
8# 0x0000000000361B71 in /usr/lib/libQt6Gui.so.6
9# QFontMetrics::size(int, QString const&, int, int*) const in /usr/lib/libQt6Gui.so.6
10# QCommonStyle::sizeFromContents(QStyle::ContentsType, QStyleOption const*, QSize const&, QWidget const*) const in /usr/lib/libQt6Widgets.so.6
11# QFusionStyle::sizeFromContents(QStyle::ContentsType, QStyleOption const*, QSize const&, QWidget const*) const in /usr/lib/libQt6Widgets.so.6
12# QHeaderView::sectionSizeFromContents(int) const in /usr/lib/libQt6Widgets.so.6
13# QHeaderView::sizeHint() const in /usr/lib/libQt6Widgets.so.6
14# QTreeView::updateGeometries() in /usr/lib/libQt6Widgets.so.6
15# QTreeView::doItemsLayout() in /usr/lib/libQt6Widgets.so.6
16# PeerListWidget::PeerListWidget(PropertiesWidget*) in qbittorrent
17# PropertiesWidget::PropertiesWidget(QWidget*) in qbittorrent
18# MainWindow::MainWindow(IGUIApplication*, WindowStateNS::WindowState, QString const&) in qbittorrent
19# 0x00000000001CA1BF in qbittorrent
20# 0x00000000001F081B in /usr/lib/libQt6Core.so.6
21# 0x00000000001F081B in /usr/lib/libQt6Core.so.6
22# QObject::~QObject() in /usr/lib/libQt6Core.so.6
23# 0x000000000029917A in qbittorrent
24# QObject::event(QEvent*) in /usr/lib/libQt6Core.so.6
25# QApplicationPrivate::notify_helper(QObject*, QEvent*) in /usr/lib/libQt6Widgets.so.6
26# QCoreApplication::notifyInternal2(QObject*, QEvent*) in /usr/lib/libQt6Core.so.6
27# QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) in /usr/lib/libQt6Core.so.6
28# 0x000000000049FC98 in /usr/lib/libQt6Core.so.6
29# 0x0000000000061BFD in /usr/lib/libglib-2.0.so.0
30# 0x0000000000063E57 in /usr/lib/libglib-2.0.so.0
31# g_main_context_iteration in /usr/lib/libglib-2.0.so.0
32# QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) in /usr/lib/libQt6Core.so.6
33# QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) in /usr/lib/libQt6Core.so.6
34# QCoreApplication::exec() in /usr/lib/libQt6Core.so.6
35# Application::exec() in qbittorrent
36# main in qbittorrent
37# 0x0000000000027741 in /usr/lib/libc.so.6
38# __libc_start_main in /usr/lib/libc.so.6
39# _start in qbittorrent
```

Segmentation fault (core dumped) qbittorrent

- Other apps like audacious, calibre, etc. fail with a terse Segmentation fault (core dumped)

floriv · Today 15:33:40

I had the same problem. Have you tried restarting yet? After I restarted, I had the same problem as described here:

https://bbs.archlinux.org/viewtopic.php?id=313796

floriv · Today 16:13:58

You can try downgrading fontconfig; that worked for me.

sudo pacman -U https://archive.archlinux.org/packages/f/fontconfig/fontconfig-2:2.17.1-1-x86_64.pkg.tar.zst

LudwigJ · Today 18:05:37

Indeed, downgrading fontconfig to 2:2.17.1-1 solved the problem.
This shouldn't happen, though, should it? Should we report it somewhere?

V1del · Today 18:32:03

Worksforme™ do you potentially have some other tools that might not have been rebuilt yet or similar/are you using a non-standard Qt build/theme? There was a bug in 2.18 fontconfig that "should" be fixed in 2.18.1 is that the version you were running? Some "exotic" fonts?

LudwigJ · Today 18:42:11

Non-standard Qt build/theme? No.
"Exotic" fonts? I can't imagine any of the fonts I use could be classified as "exotic", but then again I'm not sure what kind of founts would be considered "exotic".
For now it Worksforme™, which is all I care for in the short term, since I need urgent access to some documents that happen to be in epub format.
I had fontconfig 2:2.18.1-1, downgrading to 2:2.17.1-1 did the trick. Right now I can't afford to spend time investigating further, maybe tomorrow.

Last edited by LudwigJ (Today 18:43:31)

floriv · Today 18:47:44

V1del wrote:

There was a bug in 2.18 fontconfig that "should" be fixed in 2.18.1 is that the version you were running?

I tested both 2.18 versions, and the problem occurred in both. (The problem occurred this morning)

$ cat /var/log/pacman.log | grep -a fontconfig | grep -Ei 'downgrade|install|upgrade'
[2026-02-18T12:22:15+0100] [ALPM] upgraded fontconfig (2:2.17.1-1 -> 2:2.17.1-1.1)
[2026-06-03T07:48:45+0200] [ALPM] upgraded fontconfig (2:2.17.1-1.1 -> 2:2.18.1-1.1)
[2026-06-03T15:54:30+0200] [ALPM] downgraded fontconfig (2:2.18.1-1.1 -> 2:2.18.0-3)
[2026-06-03T16:04:55+0200] [ALPM] upgraded fontconfig (2:2.18.0-3 -> 2:2.18.1-1.1)
[2026-06-03T18:09:13+0200] [ALPM] downgraded fontconfig (2:2.18.1-1.1 -> 2:2.17.1-1)

V1del wrote:

Some "exotic" fonts?

Do you mean in use or in the Fonts directory? In use: No, I don't think so.

Last edited by floriv (Today 18:52:58)

seth · Today 19:43:33

x-ref, https://bbs.archlinux.org/viewtopic.php?id=313799

archdub · Today 21:47:34

After today's update, Telegram was failing for me with this message:

Telegram
error: empty dic file
Hash Manager Error : 2
QPainter::begin: Paint device returned engine == 0, type: 2
QWidget::render: Cannot render with an inactive painter
qt.gui.imageio.jpeg: Corrupt JPEG data: premature end of data segment

Downgrading (and pinning) fontconfig fixed it for me. Thanks a lot for mentioning that solution.

Update: in Arch gitlab on the issues register for fontconfig, someone suggested that running "fc-cache" would fix the issue. It did not for me. Downgrading fixed it.

Last edited by archdub (Today 22:09:47)

seth · Today 22:05:06

Do you mean in use or in the Fonts directory? In use: No, I don't think so.

Do you have the output of

fc-match -s sans-serif

for either fc version?
It seems the resolution strategy for the generic fonts has changed and something in the resolution chain tries to trigger a crash when testing the glyph coverage.

Arch Linux

#1 Today 15:20:29

Problems with Qt?

#2 Today 15:33:40

Re: Problems with Qt?

#3 Today 16:13:58

Re: Problems with Qt?

#4 Today 18:05:37

Re: Problems with Qt?

#5 Today 18:32:03

Re: Problems with Qt?

#6 Today 18:42:11

Re: Problems with Qt?

#7 Today 18:47:44

Re: Problems with Qt?

#8 Today 19:43:33

Re: Problems with Qt?

#9 Today 21:47:34

Re: Problems with Qt?

#10 Today 22:05:06

Re: Problems with Qt?

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