I needed the attached change to cross compile Octave for i686-w64-mingw32.
Without it, rpl_gethostname was undefined because w64 has a gethostname
function so gethostname.c is not added to the list of files to build but
gethostname was still being redefined to rpl_gethostname.
jwe
diff -uNr a/libgnu/unistd.in.h b/libgnu/unistd.in.h
--- a/libgnu/unistd.in.h 2016-06-18 18:47:32.000000000 -0400
+++ b/libgnu/unistd.in.h 2016-06-23 18:45:42.410781867 -0400
@@ -734,7 +734,7 @@
Null terminate it if the name is shorter than LEN.
If the host name is longer than LEN, set errno = EINVAL and return -1.
Return 0 if successful, otherwise set errno and return -1. */
-# if @UNISTD_H_HAVE_WINSOCK2_H@
+# if !@HAVE_GETHOSTNAME@ && @UNISTD_H_HAVE_WINSOCK2_H@
# if !(defined __cplusplus && defined GNULIB_NAMESPACE)
# undef gethostname
# define gethostname rpl_gethostname
