From e46e22baa6cccf1f74a9ad2cf9c6f7e066cf1a5c Mon Sep 17 00:00:00 2001
From: phil <phil@ultimate.com>
Date: Sun, 20 Oct 2019 13:55:40 -0400
Subject: [PATCH] cas.s performs zero word writes: a7out was die-ing: make it a
 noop

---
 tools/a7out | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/a7out b/tools/a7out
index 4835c1b..46b3f1e 100755
--- a/tools/a7out
+++ b/tools/a7out
@@ -1124,7 +1124,7 @@ sub sys_write {
     my $count = $Mem[ $PC + 2 ];
     my $end   = ( $start + $count - 1 ) & MAXADDR;
     die("sys_write: bad start/end addresses $start $end\n")
-      if ( $end < $start );
+      if ( $count != 0 && $end < $start );
     printf( "write: %d words from %s to fd %d\n", $count, addr($start), $fd )
 					if ( ($debug) || ($singlestep) );