While building 32-bit Tk from checkout [42c5de9b] (= core-8-6-b3-rc 2012/09/13) with MSVC2010 on Windows 7:
tk\win\..\win\tkWinWm.c(5529) : warning C4133: 'function' : incompatible types - from 'TkWindow *' to 'Tk_Window'