It is currently not tested to build 64 bit Qt and Qt applications using the following lines

QMAKE_CFLAGS += -Wp64 -W3
QMAKE_CXXFLAGS += -Wp64 -W3

as recommended from Microsoft

-> http://msdn.microsoft.com/en-us/library/aa384267(VS.85).aspx

However it would be useful if this was tested and supported as this is the official recommendation from Microsoft when
porting software to Microsoft 64bit OS. (At the moment heaps of warnings are issued when doing so).