Public bug reported:
Summary
gddccontrol prints:
I/O warning : failed to load external entity "/usr/share/ddccontrol-
db/monitor/AOC2703.xml"
Document not parsed successfully.
Error while opening ddccontrol home directory.: No such file or
directory
Then segfaults on exit.
Reinstalling ddccontrol-db, ddccontrol, gddccontrol, libddccontrol0 does
not fix it.
ddcutil works correctly with the same monitors, so this appears specific
to gddccontrol/ddccontrol-db/libddccontrol.
Environment
OS: Ubuntu 24.04 LTS (Noble)
Package versions (from apt):
gddccontrol 1.0.3-1build2
ddccontrol 1.0.3-1build2
ddccontrol-db 20240209-1
libddccontrol0 1.0.3-1build2
Monitors:
AOC U27B3AF (multiple units)
Also a Hisense/Hitachi device present where DDC fails (likely TV), but
not required to reproduce
Steps to reproduce
Install packages:
bash
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sudo apt update
sudo apt install -y gddccontrol ddccontrol ddccontrol-db
Run:
bash
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gddccontrol
Close the app (quit normally).
Expected result
gddccontrol starts, lists monitors, and exits cleanly without warnings
or crashes.
Actual result
Terminal output includes:
pgsql
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I/O warning : failed to load external entity
"/usr/share/ddccontrol-db/monitor/AOC2703.xml"
Document not parsed successfully.
Error while opening ddccontrol home directory.: No such file or directory
Segmentation fault (core dumped)
Under gdb, crash occurs during GTK widget destruction.
Additional information / Evidence
1) ddcutil detects monitors successfully
(Shows DDC works on AOC monitors; one device fails DDC)
yaml
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ddcutil detect
Invalid display
I2C bus: /dev/i2c-7
DRM connector: card1-DP-3
EDID synopsis:
Mfg id: HEC - Hitachi Engineering Company Ltd
Model: HISENSE
...
DDC communication failed
Display 1
I2C bus: /dev/i2c-9
DRM connector: card1-DP-1
EDID synopsis:
Mfg id: AOC - UNK
Model: U27B3AF
...
VCP version: 2.2
...
2) ddcutil can read brightness
java
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ddcutil -d 1 getvcp 10
VCP code 0x10 (Brightness): current value = 80, max value = 100
3) ddccontrol warns about missing/broken DB profile
vbnet
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I/O warning : failed to load external entity
"/usr/share/ddccontrol-db/monitor/AOC2703.xml"
Document not parsed successfully.
...
There is no support for your monitor in the database, but ddccontrol is using a
basic generic profile.
4) gdb backtrace on exit
bash
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Thread 1 "gddccontrol" received signal SIGSEGV, Segmentation fault.
0x00007ffff7c7c805 in IA__gtk_widget_destroy (widget=0x55555583ca40)
at .../gtk/gtkwidget.c:3187
#0 IA__gtk_widget_destroy (widget=0x55555583ca40) at .../gtkwidget.c:3187
#1 delete_monitor_manager () at notebook.c:721
#2 main (...) at main.c:607
Workarounds
ddcutil works for brightness control, so users can use CLI directly.
gddccontrol is currently unusable due to the crash.
What I suspect
gddccontrol / ddccontrol-db references a monitor XML (AOC2703.xml) that
is not shipped (or is shipped elsewhere / wrong filename), and the
failure path plus shutdown cleanup triggers a use-after-free or NULL
deref in delete_monitor_manager() / GTK cleanup.
Upstream GitHub issue (ddccontrol/ddccontrol)
Title
pgsql
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gddccontrol segfaults on exit on Ubuntu 24.04 and tries to load missing
AOC2703.xml; GTK destroy crash from delete_monitor_manager()
Describe the bug
gddccontrol emits libxml warning trying to open /usr/share/ddccontrol-
db/monitor/AOC2703.xml, then on exit it segfaults.
ddcutil works on the same monitors, so DDC is functional and this is
likely GUI/db handling.
To Reproduce
Ubuntu 24.04 (Noble)
sudo apt install gddccontrol ddccontrol ddccontrol-db
Run gddccontrol, then quit → segfault.
Expected behavior
Exit cleanly.
Actual behavior
Crash during gtk_widget_destroy call stack.
Environment
Ubuntu 24.04 LTS (Noble)
gddccontrol 1.0.3-1build2
Monitors: AOC U27B3AF (3 units), plus one non-DDC device present
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: gddccontrol (not installed)
ProcVersionSignature: Ubuntu 6.14.0-37.37~24.04.1-generic 6.14.11
Uname: Linux 6.14.0-37-generic x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sun Jan 4 07:48:58 2026
InstallationDate: Installed on 2025-11-24 (41 days ago)
InstallationMedia: Ubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
SourcePackage: ddccontrol
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: ddccontrol (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
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https://bugs.launchpad.net/bugs/2137411
Title:
gddccontrol did not recognize my monitors correctly
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