missing-qobject-macro

Finds QObject derived classes that don't have a Q_OBJECT macro.

Reasons to use Q_OBJECT

Signals and slots
QObject::inherits
qobject_cast
metaObject()->className()
Use your custom widget as a selector in Qt stylesheets

Reasons not to use Q_OBJECT

Templated QObjects
Compilation time

This check can't be used with pre-compiled headers support. This check doesn't have false positives, but it's not included in level <= 1 because the missing Q_OBJECT might be intentional.