Marble does produce a lot of "device not found" warning messages while running.

I've found out why - if MarbleDebug::isEnabled() is false, a NullDevice is created in the MarbleDebug.cpp code, but not opened - thus Qt produces qWarning every time mDebug() is called in Marble code. It happens with Qt 5.2.1 and Qt 5.3 beta (haven't tested any other version).

It's an annoying bug, but pretty easy to fix. Just open the NullDevice, maybe when constructing it:

NullDevice() { open(QIODevice::WriteOnly); }

the above line fixes the issue. I don't have an idea if this is a proper patch, but would love to see this fixed.

Thanks, committed in http://commits.kde.org/marble/14574f3