Moc is unable to parse some preprocessing lines in Boost lib (Qt bug).
One fix is to use the macro Q_MOC_RUN to prevent moc from processing OTB header files, where many boost headers are included.
More info here : https://bugreports.qt.io/browse/QTBUG-22829
Headers in Module/Wrappers/QtWidget were modified by a python script (QT4-boost-compat.py in DevUtils).
Each modified line is tagged with QT4-boost-compatibility.