/usr/include/KF5/KAlarmCal/KAlarmCal/CompatibilityAttribute is in libkf5alarmcalendar-dev 4:17.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 | #include "kalarmcal/compatibilityattribute.h"
|