diff -up diffutils-2.8.1/src/cmp.c.cmp-s-empty diffutils-2.8.1/src/cmp.c
--- diffutils-2.8.1/src/cmp.c.cmp-s-empty	2002-04-05 21:37:31.000000000 +0100
+++ diffutils-2.8.1/src/cmp.c	2010-06-25 14:56:08.464802321 +0100
@@ -316,12 +316,15 @@ main (int argc, char **argv)
 
   /* If only a return code is needed,
      and if both input descriptors are associated with plain files,
+     and if both files are larger than 0 bytes (procfs files are always 0),
      conclude that the files differ if they have different sizes
      and if more bytes will be compared than are in the smaller file.  */
 
   if (comparison_type == type_status
       && S_ISREG (stat_buf[0].st_mode)
-      && S_ISREG (stat_buf[1].st_mode))
+      && S_ISREG (stat_buf[1].st_mode)
+      && stat_buf[0].st_size > 0
+      && stat_buf[1].st_size > 0)
     {
       off_t s0 = stat_buf[0].st_size - file_position (0);
       off_t s1 = stat_buf[1].st_size - file_position (1);