I recently compiled the x11 version of cfclient for cygwin and had to do 2 minor modifications to make it compile. If it's a flaw that <errno.h> is missing it might be a good idea to remove the #ifdef __CYGWIN__ below is the output from cvs -q diff: Index: common/client.c =================================================================== RCS file: /cvsroot/crossfire/client/common/client.c,v retrieving revision 1.2 diff -r1.2 client.c 48a49,52 > #ifdef __CYGWIN__ > #include <errno.h> > #endif > Index: x11/x11.c =================================================================== RCS file: /cvsroot/crossfire/client/x11/x11.c,v retrieving revision 1.3 diff -r1.3 x11.c 89a90,94 > #ifdef __CYGWIN__ > #include <errno.h> > #endif > > /Henric (aka Gambold)