First add a new class to a project and be sure not based on QObject.
Then build the project.
Then add Q_OBJECT to the class and change the base class to QObject.
Then build again,then there will be linking error.The cause is although we add Q_OBJECT to the header,the build system still doesn't run moc.exe on the header file.
The only solution is to delete the shadow build folder.So there seems to be many data sync problem related to shadow build folder.
Similar problem is QTCREATORBUG-15658