In response to: http://lists.fedoraproject.org/pipermail/fedora-mingw/2008-November/00001... MinGW and Cygwin are wholly separate and different things. Do not confuse them. MinGW is just a compiler and some Win32 header files. Cross- compilation using MinGW (which is what the Fedora MinGW project is all about) uses Win32 API calls, and so Unix programs require significant porting efforts to work. eg. If your Unix program calls 'fork(2)', then forget it - it's never going to work under Win32 API until that dependency is removed or replaced. Cygwin is, essentially, a Unix emulator for Windows. Unix programs can usually be compiled directly for Cygwin with no changes, because Cygwin offers the familiar Unix/POSIX API to programs (by emulating it at great cost, including features like 'fork' which are not found on Windows and expensive to emulate). Cygwin has fatal licensing problems which prevent commercial use, apart from being inefficient, which is why we didn't go that route. So back to your program ... ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This is your problem - the cross-compilers that we ship are configured so they never look in /usr/include or /usr/local/include. Header files in /usr/include are for the build system (Fedora), and are wrong for the host system (Windows). If you specifically add /usr/include and /usr/local/include back in, then you'll pick up the wrong headers, and anything can go wrong from there. I gather that you didn't write Poco's build system, but you need to go back and find out why it's including this. Probably (as demonstrated by the MinGW / Cygwin confusion above), Poco either hasn't been ported to MinGW, or needs some different options to compile under a true MinGW cross-compiler. If that doesn't help, try reading my porting notes: http://camltastic.blogspot.com/2008/10/mingw-compile-software-for-windows... (or maybe I'd better say, read them again, because I see you put a comment there already). Rich. -- Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones Read my OCaml programming blog: http://camltastic.blogspot.com/ Fedora now supports 68 OCaml packages (the OPEN alternative to F#) http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora