Changing settings on a PC with different versions of QGIS with Qt5 and Qt6 generates a large QGIS3.ini file

[pigreco]

What is the bug or the crash?

I use OSGeo4w Installer and I have installed various versions of QGIS including the version with Qt6 dev. After changing the color setting of the gui (on QGIS with Qt 6.8) it is no longer possible to use QGIS with Qt5 or Qt6, everything is slowed down, starting QGIS (any version) takes a long time.

I looked at the folder 'C:\Users[username]\AppData\Roaming\QGIS\QGIS3\profiles\default\QGIS' and inside there were strange files and the QGIS3.ini file weighed over 160 MB, I analyzed the file and I noticed that dozens of lines had incredible lengths, the longest exceeded 123 million characters.

I managed to fix the QGIS3.ini file by eliminating all the lines with over 5000 characters, and now everything works again also recovering all the default profile settings.

I opened an issue because it might be useful to someone else.

Steps to reproduce the issue

read above

Versions

Versione di QGIS	3.40.6-Bratislava
Revisione codice QGIS	5d7f6a3e26
Librerie
Versione Qt	5.15.13
Versione Python	3.12.10
GDAL version	3.10.3
Versione PROJ	9.6.0
Versione database del Registro EPSG	v12.004 (2025-03-02)
Versione GEOS	3.13.1-CAPI-1.19.2
Versione SQLite	3.46.1
Versione PDAL	2.8.3
Versione client PostgreSQL	unknown
Versione SpatiaLite	5.1.0
Versione QWT	6.3.0
Versione QScintilla2	2.14.1
Versione SO	Windows 11 Version 2009
Plugins Python attivi
plugin_reloader	0.17
qduckdb	2.1.2
qgis_plugin_gpq_downloader	0.8.0
quick_map_services	0.21.2
db_manager	0.1.20
processing	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

No response