Hi, after applying Andy's patches I have problems building 21.2 under NT, because of event-msw.c ..\src\event-msw.c(76) : error C2011: 'tagNMHDR' : 'struct' type redefinition The relevant section is #ifndef CYGWIN_VERSION_DLL_MAJOR typedef struct tagNMHDR { HWND hwndFrom; UINT idFrom; UINT code; } NMHDR, *PNMHDR, *LPNMHDR; #endif I fixed the problem for me by #define'ing CYGWIN_VERSION_DLL_MAJOR right before the construct,but this isn't an option at all. Hmm, what causes the problem? CYGWIN_VERSION_DLL_MAJOR isn't defined. Therefore, the struct is declared and typedef'd. I've got cygwin (b20) installed on my machine, but do native builds. The struct is declared twice, elsewhere: ...\cygwin-b20\H-i586-cygwin32\i586-cygwin32\include\Windows32\Structure.h (line 2031) and ...\VC98\include\WINUSER.h (line 2223, VC++ 6.0) Here, it reads #if(WINVER >= 0x0400) typedef struct tagNMHDR { HWND hwndFrom; UINT idFrom; UINT code; // NM_ code } NMHDR; typedef NMHDR FAR * LPNMHDR; typedef struct tagSTYLESTRUCT { DWORD styleOld; DWORD styleNew; } STYLESTRUCT, * LPSTYLESTRUCT; #endif /* WINVER >= 0x0400 */ I guess, the VC98/include headers are used, aren't they? Thus, do we need the declaration at all for WinNT 4 and higher? Norbert.