Bug 830135 – kde-apps/dolphin-21.08.3 crashes on startup with QFont::setPointSizeF error

• Status: RESOLVED WORKSFORME
• Product: Gentoo Linux

[Description Xi 2021-12-28 03:54:43 UTC]

Previously, I had this issue, https://bugs.gentoo.org/829596, when starting Dolphin. After I upgraded systemd, the `cgroup` error is gone, but I got another error.

```
Dec 28 14:46:57 gentoo systemd[1957]: Started Dolphin - File Manager.                                                                                                                                                                                                         [201/1286]
Dec 28 14:46:57 gentoo kded5[2236]: Registering ":1.112/StatusNotifierItem" to system tray
Dec 28 14:46:57 gentoo plasmashell[2286]: QFont::setPointSizeF: Point size <= 0 (0.000000), must be greater than 0
Dec 28 14:46:57 gentoo plasmashell[2286]: file:///usr/share/plasma/plasmoids/org.kde.plasma.taskmanager/contents/ui/Task.qml:377: Unable to assign [undefined] to QString
```

Reproducible: Always

Steps to Reproduce:
1. Emerge kde-apps/dolphin-21.08.3 and sys-apps/systemd-249.7
2. Start Dolphin
3.
Actual Results:  
Dolphin crashes on startup

Expected Results:  
Dolphin starts

After the Dolphin crashed for a while, I got this massive error (attached) in my journal log. A similar error also occurs when I try to launch KCalc, but not Kate.

[Comment 1 Xi 2021-12-28 03:55:50 UTC]

Created attachment 760605 [details]
dolphin crash log

[Comment 2 Xi 2021-12-28 05:36:06 UTC]

Created attachment 760608 [details]
systemd core dump

[Comment 3 Xi 2021-12-28 05:37:20 UTC]

Created attachment 760609 [details]
kcrash info for Dolphin

[Comment 4 Xi 2021-12-29 02:00:53 UTC]

After taking sam's advice to recompile plasma related packages using GCC, I can use dolphin and KCalc now. I don't think recompiling ALL plasma packages is necessary, since most of the system works with clang, but since qt5 is not actively maintained upstream, I suspect more clang compiling related issues may occur in the future until we move to qt6.

[Comment 5 Andreas Sturmlechner 2021-12-29 08:55:13 UTC]

I doubt recompiling Plasma packages helps at all, since dolphin has no dependencies on it. But hey, there you go.

[Comment 6 Sam James 2021-12-29 09:04:26 UTC]

For posterity: my advice was to rebuild Qt bits with GCC rather than Clang given the changes in LLVM 13 which seem to end up manifesting as UB-causing-null-or-near-null pointers. Unless a decent bug report is made to Qt upstream and they fix it, there's not much prospect of us getting it fixed.

So easier to just use GCC.

[Comment 7 Andreas Sturmlechner 2021-12-29 09:12:20 UTC]

There are various UB related fixes in upstream's 5.15 branch not yet picked in KDE repos.

https://invent.kde.org/groups/qt/-/issues?scope=all&state=opened&search=ub