diff --no-dereference -uNr tcludp-1.0.11.orig/generic/udp_tcl.c tcludp-1.0.11-fixerrno/generic/udp_tcl.c
--- tcludp-1.0.11.orig/generic/udp_tcl.c 2014-08-24 02:17:21.000000000 -0500
+++ tcludp-1.0.11-fixerrno/generic/udp_tcl.c 2019-01-18 09:57:47.320471347 -0600
@@ -31,6 +31,9 @@
#error "Neither sys/ioctl.h nor sys/filio.h found. We need ioctl()"
#endif
#endif /* WIN32 */
+#if defined(HAVE_STRERROR)
+#include <string.h>
+#endif
#if HAVE_FCNTL_H
# include <fcntl.h>
@@ -1833,7 +1836,6 @@
Tcl_AppendUnicodeToObj(errObj, (LPWSTR)sMsg, len - 1);
LocalFree(sMsg);
#elif defined(HAVE_STRERROR)
- extern int errno;
errObj = Tcl_NewStringObj(prefix, -1);
Tcl_AppendStringsToObj(errObj, ": ", strerror(errno), NULL);
#endif