Index: signed.c
--- signed.c.orig
+++ signed.c
@@ -32,12 +32,13 @@ to preserve same.
 */
 #include "xplot.h"
 #include <stdio.h>
+#include <stdlib.h>
 
 char *signed_unparse(coord c)
 {
   char *r;
   char buf[50];
-  (void) sprintf(buf,"%d",c.i);
+  (void) sprintf(buf,"%ld",c.i);
   r = malloc((unsigned) strlen(buf)+1);
   if (r == 0)
     fatalerror("malloc returned 0");
@@ -48,9 +49,11 @@ char *signed_unparse(coord c)
 coord signed_parse(char *s)
 {
   coord r;
-  extern int atoi();
+  const char *errstr;
 
-  r.i = atoi(s);
+  r.i = strtonum(s, LONG_MIN, LONG_MAX, &errstr);
+  if (errstr != NULL)
+    fprintf(stderr, "warning: signed_parse value is %s: %s\n", errstr, s);
   return r;
 }