From 68d4a61bf1cf321cc03ce45d0082c28de986ffce Mon Sep 17 00:00:00 2001
From: Larry Masinter <LMM@acm.org>
Date: Sat, 15 May 2021 12:21:06 -0700
Subject: [PATCH] WIP: make variable types in simulate_unbind match OP_unbind

---
 src/mvs.c | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/mvs.c b/src/mvs.c
index 90592d9..8d60b5c 100644
--- a/src/mvs.c
+++ b/src/mvs.c
@@ -69,6 +69,8 @@ newframe:
     fnhead = (struct fnhead *)FuncObj;
     pc = (ByteCode *)PC + 3; /* to skip the miscn opcode we're in now */
   } else {
+    unbind_count = 0; /* different frame */
+
     fnhead = (struct fnhead *)Addr68k_from_LADDR(POINTERMASK & SWA_FNHEAD((int)caller->fnheader));
     pc = (ByteCode *)fnhead + (caller->pc);
   }
@@ -271,23 +273,25 @@ LispPTR make_value_list(int argcount, LispPTR *argarray) {
 
 void simulate_unbind(FX2 *frame, int unbind_count, FX2 *returner) {
   int unbind;
-  LispPTR *stackptr = (LispPTR *)(Stackspace + frame->nextblock);
+  LispPTR *stack_pointer = (LispPTR *)(Stackspace + frame->nextblock);
   for (unbind = 0; unbind < unbind_count; unbind++) {
-    register int value;
-    register LispPTR *lastpvar;
-    int bindnvalues;
-    for (; ((int)*--stackptr >= 0);)
-      ; /* find the binding mark */
-    value = (int)*stackptr;
-    lastpvar = (LispPTR *)((DLword *)frame + FRAMESIZE + 2 + GetLoWord(value));
-    ;
-    bindnvalues = (~value) >> 16;
-    for (value = bindnvalues; --value >= 0;) { *--lastpvar = 0xffffffff; }
-    /* This line caused \NSMAIL.READ.HEADING to smash memory, */
-    /* so I removed it 21 Jul 91 --JDS.  This was the only	  */
-    /* difference between this function and the UNWIND code   */
-    /* in inlineC.h						  */
-    /*	MAKEFREEBLOCK(stackptr, (DLword *)stackptr-nextblock); */
+    register LispPTR value;
+    register LispPTR *ppvar;
+    register DLword num;
+    register DLword i;
+    
+    /* now, stack_pointer points the latter part in slot */
+    for (; !(*--stack_pointer & 0x80000000);)
+      ; /* scan (until MSB == 1) */
+
+    value = *stack_pointer;
+    num = (DLword) ~(value >> 16);
+    ppvar = (LispPTR *)((DLword *)frame + FRAMESIZE + 2 + GetLoWord(value));
+
+    value = 0xffffffff;
+    for (i = 0; i < num; i++) { *--ppvar = value; }
+
+    /* MAKEFREEBLOCK(stack_pointer, (DLword *)stack_pointer-nextblock); */
   }
   if (returner)
     returner->fast = 0; /* since we've destroyed contiguity */