Qmake builds for MSVC.

I _think_ MSVC would want "/Wall" but qmake is giving it "-Wall" might be worth backing up and editing the relevant &lt;QtBaseDir&gt;gcc/mkspecs/win32-msvc20##/qmake.conf file to change say the:
    
    QMAKE_CFLAGS_WARN_ON    = -W3
    QMAKE_CFLAGS_WARN_OFF  = -W0
    
lines to:
    
    QMAKE_CFLAGS_WARN_ON    = /W3
    QMAKE_CFLAGS_WARN_OFF   = /W0

and see if the CONFIG += warn_on or warn_off _THEN_  work.  That being the case then Qt people have messed up (of course it may tie in with Windoze path mangling but as I say they do use '/' as the command line argument prefix for the linker so why not the complier?)