diff -ub -r mpack-1.6-orig/unixos.c mpack-1.6/unixos.c
--- mpack-1.6-orig/unixos.c	2003-07-21 22:54:05.000000000 +0200
+++ mpack-1.6/unixos.c	2009-01-12 17:11:50.000000000 +0100
@@ -23,6 +23,7 @@
  * SOFTWARE.
  */
 #include <stdio.h>
+#include <stdlib.h>
 #include <ctype.h>
 #include <string.h>
 #include <errno.h>
@@ -38,10 +39,6 @@
 #define MAXHOSTNAMELEN 64
 #endif
 
-extern int errno;
-extern char *malloc();
-extern char *getenv();
-
 int overwrite_files = 0;
 int didchat;
 
diff -ub -r mpack-1.6-orig/unixpk.c mpack-1.6/unixpk.c
--- mpack-1.6-orig/unixpk.c	2003-07-21 22:50:41.000000000 +0200
+++ mpack-1.6/unixpk.c	2009-01-12 17:11:32.000000000 +0100
@@ -23,6 +23,9 @@
  * SOFTWARE.
  */
 #include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <getopt.h>
 #include <string.h>
 #include <errno.h>
 #include "common.h"
@@ -31,12 +34,6 @@
 
 #define MAXADDRESS 100
 
-extern char *getenv();
-
-extern int errno;
-extern int optind;
-extern char *optarg;
-
 void usage(void);
 void sendmail(FILE *infile, char **addr, int start);
 void inews(FILE *infile);
diff -ub -r mpack-1.6-orig/unixunpk.c mpack-1.6/unixunpk.c
--- mpack-1.6-orig/unixunpk.c	2003-07-21 22:51:55.000000000 +0200
+++ mpack-1.6/unixunpk.c	2009-01-12 17:12:25.000000000 +0100
@@ -23,6 +23,7 @@
  * SOFTWARE.
  */
 #include <stdio.h>
+#include <stdlib.h>
 #include "version.h"
 #include "part.h"
 
diff -ub -r mpack-1.6-orig/xmalloc.c mpack-1.6/xmalloc.c
--- mpack-1.6-orig/xmalloc.c	2003-07-21 22:35:31.000000000 +0200
+++ mpack-1.6/xmalloc.c	2009-01-12 17:12:07.000000000 +0100
@@ -23,8 +23,8 @@
  * SOFTWARE.
  */
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-extern char *malloc(), *realloc();
 
 char *xmalloc (int size)
 {