In upgrading Qt from 5.2.1 to 5.3.1, it was discovered that the Menu Merge feature of QAction and QMenuBar did not operate the same on a previously released application. Exit, About and Preferences menu items that were normally Merged into the Application Menu were no longer being moved.
Trial and error testing showed that the "string matching" on the text of the QAction was significantly different. This will affect the operation of existing application code and is not backwards compatible
A sample application is attached. The application operates as expected on 5.2.1, but the menus are not merged on 5.3.1. Some additional working and non-working example lines are shown in the CreateActions() routine in mainwindow.cpp