In file included from ../windows/window.c:29:0: D:/CodeBlocks/MinGW/i686-w64-mingw32/include/multimon.h: In function 'IsPlatformNT': D:/CodeBlocks/MinGW/i686-w64-mingw32/include/multimon.h:130:38: error: 'osvi' undeclared (first use in this function) oi.dwOSVersionInfoSize = sizeof (osvi); ^~~~ D:/CodeBlocks/MinGW/i686-w64-mingw32/include/multimon.h:130:38: note: each undeclared identifier is reported only once for each function it appears in mingw32-make: *** [.\Makefile.mgw:963: window.o] Error 1