From d625665cde1f38496b3bf3ac36d71c7d758f8018 Mon Sep 17 00:00:00 2001
From: Larry Masinter <LMM@acm.org>
Date: Mon, 24 May 2021 12:26:31 -0700
Subject: [PATCH] WIP still, trying for a fix

---
 bin/makefile-linux.x86_64-x |  2 +-
 inc/stack.h                 |  8 ++++----
 src/hardrtn.c               |  9 +++++++--
 src/mvs.c                   | 13 +++++++++----
 4 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/bin/makefile-linux.x86_64-x b/bin/makefile-linux.x86_64-x
index f280cba..f2dafe3 100644
--- a/bin/makefile-linux.x86_64-x
+++ b/bin/makefile-linux.x86_64-x
@@ -17,7 +17,7 @@ XFILES = $(OBJECTDIR)xmkicon.o \
 XFLAGS = -DXWINDOW
 
 # OPTFLAGS is normally -O2.
-OPTFLAGS =  -O2 -g3
+OPTFLAGS =  -O0 -g3
 DFLAGS = $(XFLAGS) -DRELEASE=351
 
 LDFLAGS = -L/usr/X11/lib -lX11 -lc -lm
diff --git a/inc/stack.h b/inc/stack.h
index 7aac6c4..4f3606a 100644
--- a/inc/stack.h
+++ b/inc/stack.h
@@ -78,7 +78,7 @@ typedef struct fnhead {
 typedef struct frameex1 {
   unsigned flags : 3;
   unsigned fast : 1;
-  unsigned nil2 : 1; /* not used, prev: This frame treats N-func */
+  unsigned mvscase : 1; /* was not used, prev: This frame treats N-func */
   unsigned incall : 1;
   unsigned validnametable : 1;
   /* 0: look for FunctionHeader
@@ -109,7 +109,7 @@ typedef struct frameex1 {
 typedef struct frameex2 {
   unsigned flags : 3;
   unsigned fast : 1;
-  unsigned nil2 : 1; /* not used, prev: This frame treats N-func */
+  unsigned mvscase : 1; /* not used, prev: This frame treats N-func */
   unsigned incall : 1;
   unsigned validnametable : 1;
   /* 0: look for FunctionHeader
@@ -200,7 +200,7 @@ typedef struct frameex1 {
   /* 0: look for FunctionHeader
      1: look for NameTable on this FrameEx */
   unsigned incall : 1;
-  unsigned nil2 : 1; /* not used, prev: This frame treats N-func */
+  unsigned mvscase : 1; /* not used, prev: This frame treats N-func */
   unsigned fast : 1;
   unsigned flags : 3; /* hi word */
 
@@ -235,7 +235,7 @@ typedef struct frameex2 {
   /* 0: look for FunctionHeader
      1: look for NameTable on this FrameEx */
   unsigned incall : 1;
-  unsigned nil2 : 1; /* not used, prev: This frame treats N-func */
+  unsigned mvscase : 1; /* not used, prev: This frame treats N-func */
   unsigned fast : 1;
   unsigned flags : 3;
 
diff --git a/src/hardrtn.c b/src/hardrtn.c
index 6ed187e..0ddfa61 100644
--- a/src/hardrtn.c
+++ b/src/hardrtn.c
@@ -211,8 +211,13 @@ retry: /* this is retry entry after MAKE_FXCOPY etc */
     } else {
       if (CURRENTFX->nopush) {
         CURRENTFX->nopush = NIL;
-        CurrentStackPTR = next68k - 2;
-        TopOfStack = *((LispPTR *)CurrentStackPTR);
+        if (CURRENTFX->mvscase) {
+	  CurrentStackPTR = next68k;
+	  CURRENTFX->mvscase = NIL;
+	} else {
+	  CurrentStackPTR = next68k - 2;
+	  TopOfStack = *((LispPTR *)CurrentStackPTR);
+	}
         CurrentStackPTR -= 2;
 
       } else
diff --git a/src/mvs.c b/src/mvs.c
index dd92d34..b4de634 100644
--- a/src/mvs.c
+++ b/src/mvs.c
@@ -100,9 +100,14 @@ newpc:
         /* BUT 3's not enough for big atoms, so add diff between FN op size & MISCN op size */
         if (caller == immediate_caller) PC = pc + (FN_OPCODE_SIZE - 3);
 #endif /* BIGATOMS */
-
-        else
+        else {
           caller->pc = (UNSIGNED)pc + FN_OPCODE_SIZE - (UNSIGNED)fnhead;
+	  /* skip over FN opcode when we get there */
+	  prevcaller->fast = 0;
+	  caller->mvscase = 1;
+	  caller->nopush = 1;
+	}
+	
         return (make_value_list(arg_count, args));
       }
       break;
@@ -287,8 +292,8 @@ void simulate_unbind(FX2 *frame, int unbind_count, FX2 *returner) {
     ppvar = (LispPTR *)((DLword *)frame + FRAMESIZE + 2 + GetLoWord(value));
     for (i = num; --i >= 0;) { *--ppvar = 0xffffffff; }         
   }
-  if (returner)
-    returner->fast = 0; /* since we've destroyed contiguity */
+  /* if (returner)	
+    returner->fast = 0; since we've destroyed contiguity */
                         /* in the stack, but that only
                            matters if there's a return. */
 }