From 265f4b49e5c2bbf66401b43b2aac42c80be75491 Mon Sep 17 00:00:00 2001
From: Richard Cornwell <rich@sky-visions.com>
Date: Sun, 7 Nov 2021 12:04:28 -0500
Subject: [PATCH] IBM360: Fixed bug in AP instruction, thanks to Roberto Sancho
 for finding this.

---
 IBM360/ibm360_cpu.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/IBM360/ibm360_cpu.c b/IBM360/ibm360_cpu.c
index ff1cbd4..ba403b5 100644
--- a/IBM360/ibm360_cpu.c
+++ b/IBM360/ibm360_cpu.c
@@ -5750,7 +5750,8 @@ dec_add(int op, uint32 addr1, uint8 len1, uint32 addr2, uint8 len2)
 
     if (op & 1)
         sb = !sb;
-    len = 2*(len+1)+1;
+    /* Length is 1 plus number of digits times two, including the sign nibble. */
+    len = 2*(len+1)-1;
     /* On all but ZAP load first operand */
     if ((op & 3) != 0) {
         if (dec_load(a, addr1, (int)len1, &sa))
@@ -5765,7 +5766,7 @@ dec_add(int op, uint32 addr1, uint8 len1, uint32 addr2, uint8 len2)
     cy = addsub;
     zero = 1;
     /* Add numbers together */
-    for (i = 1; i < len; i++) {
+    for (i = 1; i <= len; i++) {
         acc = b[i] + ((addsub)? (0x9 - a[i]):a[i]) + cy;
         if (acc > 0x9)
            acc += 0x6;
@@ -5784,7 +5785,7 @@ dec_add(int op, uint32 addr1, uint8 len1, uint32 addr2, uint8 len2)
            /* We need to recomplent the result */
            cy = 1;
            zero = 1;
-           for (i = 1; i < len; i++) {
+           for (i = 1; i <= len; i++) {
                 acc = (0x9 - a[i]) + cy;
                 if (acc > 0x9)
                    acc += 0x6;
@@ -5803,7 +5804,7 @@ dec_add(int op, uint32 addr1, uint8 len1, uint32 addr2, uint8 len2)
     if ((op & 3) != 1) {
         if (!zero && !ov) {
            /* Start at len1 and go to len2 and see if any non-zero digits */
-           for (i = (len1+1)*2; i < len; i++) {
+           for (i = (len1+1)*2; i <= len; i++) {
                if (a[i] != 0) {
                   ov = 1;
                   break;