attempt to clear stale references on VM C stack

* libguile/vm-engine.h (DEAD): New macro, nulls out a value.

* libguile/vm-i-system.c:
* libguile/vm-i-loader.c:
* libguile/vm-i-scheme.c: Use DEAD when variables become dead.

Later we can #ifdef this out, but I want to give the buildbots a try
with this patch to make sure it's correct.

diff --git a/libguile/vm-engine.h b/libguile/vm-engine.h
index 000397d..52467c2 100644 (file)
--- a/libguile/vm-engine.h
+++ b/libguile/vm-engine.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -152,6 +152,8 @@
 #define ASSERT_BOUND(x)
 #endif
 
+#define DEAD(v) v = SCM_UNDEFINED
+
 #if VM_CHECK_OBJECT
 #define SET_OBJECT_COUNT(n) object_count = n
 #else
@@ -325,6 +327,7 @@ do                                          \
       CONS (l, x, l);                           \
     }                                           \
   PUSH (l);                                    \
+  DEAD (l);                                     \
 } while (0)
 
 /* The opposite: push all of the elements in L onto the list. */
@@ -350,7 +353,9 @@ do {                                                \
       CONS (l, o, l);                          \
       POP (o);                                 \
     }                                          \
+  DEAD (o);                                     \
   PUSH (l);                                    \
+  DEAD (l);                                     \
 } while (0)
 
 #define POP_CONS_MARK()                                \
@@ -363,7 +368,9 @@ do {                                                \
       CONS (l, o, l);                          \
       POP (o);                                 \
     }                                          \
+  DEAD (o);                                     \
   PUSH (l);                                    \
+  DEAD (l);                                     \
 } while (0)
 
 \f

diff --git a/libguile/vm-i-loader.c b/libguile/vm-i-loader.c
index 6fa8eb2..19f5271 100644 (file)
--- a/libguile/vm-i-loader.c
+++ b/libguile/vm-i-loader.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001,2008,2009,2010,2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001,2008,2009,2010,2011,2012 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -73,6 +73,9 @@ VM_DEFINE_LOADER (104, load_program, "load-program")
 
   PUSH (scm_make_program (objcode, objs, SCM_BOOL_F));
 
+  DEAD (objs);
+  DEAD (objcode);
+
   ip += len;
 
   NEXT;
@@ -84,6 +87,7 @@ VM_DEFINE_INSTRUCTION (105, link_now, "link-now", 0, 1, 1)
   POP (what);
   SYNC_REGISTER ();
   PUSH (resolve_variable (what, scm_current_module ()));
+  DEAD (what);
   NEXT;
 }
 
@@ -95,6 +99,8 @@ VM_DEFINE_LOADER (106, load_array, "load-array")
   POP2 (shape, type);
   SYNC_REGISTER ();
   PUSH (scm_from_contiguous_typed_array (type, shape, ip, len));
+  DEAD (type);
+  DEAD (shape);
   ip += len;
   NEXT;
 }

diff --git a/libguile/vm-i-scheme.c b/libguile/vm-i-scheme.c
index 243e1a3..fa1179e 100644 (file)
--- a/libguile/vm-i-scheme.c
+++ b/libguile/vm-i-scheme.c
@@ -33,6 +33,7 @@ VM_DEFINE_FUNCTION (128, not, "not", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (scm_is_false (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -40,6 +41,7 @@ VM_DEFINE_FUNCTION (129, not_not, "not-not", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (!scm_is_false (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -47,6 +49,8 @@ VM_DEFINE_FUNCTION (130, eq, "eq?", 2)
 {
   ARGS2 (x, y);
   RETURN (scm_from_bool (scm_is_eq (x, y)));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -54,6 +58,8 @@ VM_DEFINE_FUNCTION (131, not_eq, "not-eq?", 2)
 {
   ARGS2 (x, y);
   RETURN (scm_from_bool (!scm_is_eq (x, y)));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -61,6 +67,7 @@ VM_DEFINE_FUNCTION (132, nullp, "null?", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (scm_is_null (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -68,6 +75,7 @@ VM_DEFINE_FUNCTION (133, not_nullp, "not-null?", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (!scm_is_null (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -83,6 +91,8 @@ VM_DEFINE_FUNCTION (134, eqv, "eqv?", 2)
       SYNC_REGISTER ();
       RETURN (scm_eqv_p (x, y));
     }
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -98,6 +108,8 @@ VM_DEFINE_FUNCTION (135, equal, "equal?", 2)
       SYNC_REGISTER ();
       RETURN (scm_equal_p (x, y));
     }
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -105,6 +117,7 @@ VM_DEFINE_FUNCTION (136, pairp, "pair?", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (scm_is_pair (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -112,6 +125,7 @@ VM_DEFINE_FUNCTION (137, listp, "list?", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (scm_ilength (x) >= 0));
+  DEAD (x);
   NEXT;
 }
 
@@ -119,6 +133,7 @@ VM_DEFINE_FUNCTION (138, symbolp, "symbol?", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (scm_is_symbol (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -126,6 +141,7 @@ VM_DEFINE_FUNCTION (139, vectorp, "vector?", 1)
 {
   ARGS1 (x);
   RETURN (scm_from_bool (SCM_I_IS_VECTOR (x)));
+  DEAD (x);
   NEXT;
 }
 
@@ -139,6 +155,8 @@ VM_DEFINE_FUNCTION (140, cons, "cons", 2)
   ARGS2 (x, y);
   CONS (x, x, y);
   RETURN (x);
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -155,6 +173,7 @@ VM_DEFINE_FUNCTION (141, car, "car", 1)
   ARGS1 (x);
   VM_VALIDATE_CONS (x, "car");
   RETURN (SCM_CAR (x));
+  DEAD (x);
   NEXT;
 }
 
@@ -163,6 +182,7 @@ VM_DEFINE_FUNCTION (142, cdr, "cdr", 1)
   ARGS1 (x);
   VM_VALIDATE_CONS (x, "cdr");
   RETURN (SCM_CDR (x));
+  DEAD (x);
   NEXT;
 }
 
@@ -172,6 +192,8 @@ VM_DEFINE_INSTRUCTION (143, set_car, "set-car!", 0, 2, 0)
   POP2 (y, x);
   VM_VALIDATE_CONS (x, "set-car!");
   SCM_SETCAR (x, y);
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -181,6 +203,8 @@ VM_DEFINE_INSTRUCTION (144, set_cdr, "set-cdr!", 0, 2, 0)
   POP2 (y, x);
   VM_VALIDATE_CONS (x, "set-cdr!");
   SCM_SETCDR (x, y);
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -201,6 +225,8 @@ VM_DEFINE_INSTRUCTION (144, set_cdr, "set-cdr!", 0, 2, 0)
         SYNC_REGISTER ();                                               \
         RETURN (srel (x, y));                                           \
       }                                                                 \
+    DEAD (x);                                                           \
+    DEAD (y);                                                           \
     NEXT;                                                               \
   }
 
@@ -250,11 +276,15 @@ VM_DEFINE_FUNCTION (149, ge, "ge?", 2)
         if (SCM_FIXABLE (n))                                    \
           {                                                     \
             RETURN (SCM_I_MAKINUM (n));                         \
+            DEAD (x);                                           \
+            DEAD (y);                                           \
             NEXT;                                               \
           }                                                     \
       }                                                         \
     SYNC_REGISTER ();                                           \
     RETURN (SFUNC (x, y));                                      \
+    DEAD (x);                                                   \
+    DEAD (y);                                                   \
     NEXT;                                                       \
   }
 
@@ -319,6 +349,8 @@ VM_DEFINE_FUNCTION (150, add, "add", 2)
   ASM_ADD (x, y);
   SYNC_REGISTER ();
   RETURN (scm_sum (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 #endif
 }
@@ -340,12 +372,15 @@ VM_DEFINE_FUNCTION (151, add1, "add1", 1)
       if (SCM_LIKELY (SCM_I_INUMP (result)))
         {
           RETURN (result);
+          DEAD (result);
           NEXT;
         }
+      DEAD (result);
     }
 
   SYNC_REGISTER ();
   RETURN (scm_sum (x, SCM_I_MAKINUM (1)));
+  DEAD (x);
   NEXT;
 }
 
@@ -358,6 +393,8 @@ VM_DEFINE_FUNCTION (152, sub, "sub", 2)
   ASM_SUB (x, y);
   SYNC_REGISTER ();
   RETURN (scm_difference (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 #endif
 }
@@ -379,12 +416,15 @@ VM_DEFINE_FUNCTION (153, sub1, "sub1", 1)
       if (SCM_LIKELY (SCM_I_INUMP (result)))
         {
           RETURN (result);
+          DEAD (result);
           NEXT;
         }
+      DEAD (result);
     }
 
   SYNC_REGISTER ();
   RETURN (scm_difference (x, SCM_I_MAKINUM (1)));
+  DEAD (x);
   NEXT;
 }
 
@@ -396,6 +436,8 @@ VM_DEFINE_FUNCTION (154, mul, "mul", 2)
   ARGS2 (x, y);
   SYNC_REGISTER ();
   RETURN (scm_product (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -404,6 +446,8 @@ VM_DEFINE_FUNCTION (155, div, "div", 2)
   ARGS2 (x, y);
   SYNC_REGISTER ();
   RETURN (scm_divide (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -412,6 +456,8 @@ VM_DEFINE_FUNCTION (156, quo, "quo", 2)
   ARGS2 (x, y);
   SYNC_REGISTER ();
   RETURN (scm_quotient (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -420,6 +466,8 @@ VM_DEFINE_FUNCTION (157, rem, "rem", 2)
   ARGS2 (x, y);
   SYNC_REGISTER ();
   RETURN (scm_remainder (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -428,6 +476,8 @@ VM_DEFINE_FUNCTION (158, mod, "mod", 2)
   ARGS2 (x, y);
   SYNC_REGISTER ();
   RETURN (scm_modulo (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -440,6 +490,8 @@ VM_DEFINE_FUNCTION (159, ash, "ash", 2)
         /* Right shift, will be a fixnum. */
         {
           RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) >> -SCM_I_INUM (y)));
+          DEAD (x);
+          DEAD (y);
           NEXT;
         }
       else
@@ -455,6 +507,8 @@ VM_DEFINE_FUNCTION (159, ash, "ash", 2)
                   (SCM_SRS (nn, (SCM_I_FIXNUM_BIT-1 - bits_to_shift)) + 1)
                   <= 1))
             {
+              DEAD (x);
+              DEAD (y);
               RETURN (SCM_I_MAKINUM (nn << bits_to_shift));
               NEXT;
             }
@@ -464,6 +518,8 @@ VM_DEFINE_FUNCTION (159, ash, "ash", 2)
     }
   SYNC_REGISTER ();
   RETURN (scm_ash (x, y));
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -477,6 +533,8 @@ VM_DEFINE_FUNCTION (160, logand, "logand", 2)
       SYNC_REGISTER ();
       RETURN (scm_logand (x, y));
     }
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -490,6 +548,8 @@ VM_DEFINE_FUNCTION (161, logior, "logior", 2)
       SYNC_REGISTER ();
       RETURN (scm_logior (x, y));
     }
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -503,6 +563,8 @@ VM_DEFINE_FUNCTION (162, logxor, "logxor", 2)
       SYNC_REGISTER ();
       RETURN (scm_logxor (x, y));
     }
+  DEAD (x);
+  DEAD (y);
   NEXT;
 }
 
@@ -525,6 +587,8 @@ VM_DEFINE_FUNCTION (163, vector_ref, "vector-ref", 2)
       SYNC_REGISTER ();
       RETURN (scm_vector_ref (vect, idx));
     }
+  DEAD (vect);
+  DEAD (idx);
   NEXT;
 }
 
@@ -543,6 +607,9 @@ VM_DEFINE_INSTRUCTION (164, vector_set, "vector-set", 0, 3, 0)
       SYNC_REGISTER ();
       scm_vector_set_x (vect, idx, val);
     }
+  DEAD (vect);
+  DEAD (idx);
+  DEAD (val);
   NEXT;
 }
 
@@ -558,8 +625,10 @@ VM_DEFINE_INSTRUCTION (165, make_array, "make-array", 3, -1, 1)
   SYNC_REGISTER ();
   PRE_CHECK_UNDERFLOW (len);
   ret = scm_from_contiguous_array (shape, sp - len + 1, len);
+  DEAD (shape);
   DROPN (len);
   PUSH (ret);
+  DEAD (ret);
   NEXT;
 }
 
@@ -579,6 +648,7 @@ VM_DEFINE_FUNCTION (166, struct_p, "struct?", 1)
 {
   ARGS1 (obj);
   RETURN (scm_from_bool (SCM_STRUCTP (obj)));
+  DEAD (obj);
   NEXT;
 }
 
@@ -587,6 +657,7 @@ VM_DEFINE_FUNCTION (167, struct_vtable, "struct-vtable", 1)
   ARGS1 (obj);
   VM_VALIDATE_STRUCT (obj, "struct_vtable");
   RETURN (SCM_STRUCT_VTABLE (obj));
+  DEAD (obj);
   NEXT;
 }
 
@@ -616,9 +687,11 @@ VM_DEFINE_INSTRUCTION (168, make_struct, "make-struct", 2, -1, 1)
     }
   else
     ret = scm_c_make_structv (vtable, 0, n - 1, (scm_t_bits *) inits);
+  DEAD (vtable);
 
   DROPN (n);
   PUSH (ret);
+  DEAD (ret);
 
   NEXT;
 }
@@ -646,12 +719,16 @@ VM_DEFINE_FUNCTION (169, struct_ref, "struct-ref", 2)
        {
           scm_t_bits *data = SCM_STRUCT_DATA (obj);
           RETURN (SCM_PACK (data[index]));
+          DEAD (obj);
+          DEAD (pos);
           NEXT;
        }
     }
 
   SYNC_REGISTER ();
   RETURN (scm_struct_ref (obj, pos));
+  DEAD (obj);
+  DEAD (pos);
   NEXT;
 }
 
@@ -677,13 +754,20 @@ VM_DEFINE_FUNCTION (170, struct_set, "struct-set", 3)
        {
           scm_t_bits *data = SCM_STRUCT_DATA (obj);
           data[index] = SCM_UNPACK (val);
+          /* FIXME: Shouldn't be returning anything, right? */
           RETURN (val);
+          DEAD (obj);
+          DEAD (pos);
+          DEAD (val);
           NEXT;
        }
     }
 
   SYNC_REGISTER ();
   RETURN (scm_struct_set_x (obj, pos, val));
+  DEAD (obj);
+  DEAD (pos);
+  DEAD (val);
   NEXT;
 }
 
@@ -701,6 +785,7 @@ VM_DEFINE_FUNCTION (171, class_of, "class-of", 1)
       SYNC_REGISTER ();
       RETURN (scm_class_of (obj));
     }
+  DEAD (obj);
   NEXT;
 }
 
@@ -710,7 +795,9 @@ VM_DEFINE_FUNCTION (172, slot_ref, "slot-ref", 2)
   size_t slot;
   ARGS2 (instance, idx);
   slot = SCM_I_INUM (idx);
+  DEAD (idx);
   RETURN (SCM_PACK (SCM_STRUCT_DATA (instance) [slot]));
+  DEAD (instance);
   NEXT;
 }
 
@@ -721,7 +808,10 @@ VM_DEFINE_INSTRUCTION (173, slot_set, "slot-set", 0, 3, 0)
   size_t slot;
   POP3 (val, idx, instance);
   slot = SCM_I_INUM (idx);
+  DEAD (idx);
   SCM_STRUCT_DATA (instance) [slot] = SCM_UNPACK (val);
+  DEAD (instance);
+  DEAD (val);
   NEXT;
 }
 
@@ -746,11 +836,17 @@ VM_DEFINE_INSTRUCTION (173, slot_set, "slot-set", 0, 3, 0)
   SCM endianness;                                                       \
   POP (endianness);                                                     \
   if (scm_is_eq (endianness, scm_i_native_endianness))                  \
-    goto VM_LABEL (bv_##stem##_native_ref);                             \
+    {                                                                   \
+      DEAD (endianness);                                                \
+      goto VM_LABEL (bv_##stem##_native_ref);                           \
+    }                                                                   \
   {                                                                     \
     ARGS2 (bv, idx);                                                    \
     SYNC_REGISTER ();                                                  \
     RETURN (scm_bytevector_##fn_stem##_ref (bv, idx, endianness));      \
+    DEAD (bv);                                                          \
+    DEAD (idx);                                                         \
+    DEAD (endianness);                                                  \
     NEXT;                                                               \
   }                                                                     \
 }
@@ -798,6 +894,8 @@ BV_REF_WITH_ENDIANNESS (f64, ieee_double)
       SYNC_REGISTER ();                                                        \
       RETURN (scm_bytevector_ ## fn_stem ## _ref (bv, idx));            \
     }                                                                  \
+  DEAD (bv);                                                            \
+  DEAD (idx);                                                           \
   NEXT;                                                                 \
 }
 
@@ -830,6 +928,8 @@ BV_REF_WITH_ENDIANNESS (f64, ieee_double)
       SYNC_REGISTER ();                                                        \
       RETURN (scm_bytevector_ ## stem ## _native_ref (bv, idx));       \
     }                                                                  \
+  DEAD (bv);                                                            \
+  DEAD (idx);                                                           \
   NEXT;                                                                 \
 }
 
@@ -851,6 +951,8 @@ BV_REF_WITH_ENDIANNESS (f64, ieee_double)
     RETURN (scm_from_double (*float_ptr));                             \
   else                                                                 \
     RETURN (scm_bytevector_ ## fn_stem ## _native_ref (bv, idx));      \
+  DEAD (bv);                                                            \
+  DEAD (idx);                                                           \
   NEXT;                                                                 \
 }
 
@@ -894,11 +996,18 @@ BV_FLOAT_REF (f64, ieee_double, double, 8)
   SCM endianness;                                                       \
   POP (endianness);                                                     \
   if (scm_is_eq (endianness, scm_i_native_endianness))                  \
-    goto VM_LABEL (bv_##stem##_native_set);                             \
+    {                                                                   \
+      DEAD (endianness);                                                \
+      goto VM_LABEL (bv_##stem##_native_set);                           \
+    }                                                                   \
   {                                                                     \
     SCM bv, idx, val; POP3 (val, idx, bv);                              \
     SYNC_REGISTER ();                                                   \
     scm_bytevector_##fn_stem##_set_x (bv, idx, val, endianness);        \
+    DEAD (bv);                                                          \
+    DEAD (idx);                                                         \
+    DEAD (val);                                                         \
+    DEAD (endianness);                                                  \
     NEXT;                                                               \
   }                                                                     \
 }
@@ -946,6 +1055,9 @@ BV_SET_WITH_ENDIANNESS (f64, ieee_double)
       SYNC_REGISTER ();                                                 \
       scm_bytevector_ ## fn_stem ## _set_x (bv, idx, val);             \
     }                                                                   \
+  DEAD (bv);                                                            \
+  DEAD (idx);                                                           \
+  DEAD (val);                                                           \
   NEXT;                                                                        \
 }
 
@@ -970,6 +1082,9 @@ BV_SET_WITH_ENDIANNESS (f64, ieee_double)
       SYNC_REGISTER ();                                                 \
       scm_bytevector_ ## stem ## _native_set_x (bv, idx, val);         \
     }                                                                   \
+  DEAD (bv);                                                            \
+  DEAD (idx);                                                           \
+  DEAD (val);                                                           \
   NEXT;                                                                 \
 }
 
@@ -994,6 +1109,9 @@ BV_SET_WITH_ENDIANNESS (f64, ieee_double)
       SYNC_REGISTER ();                                                 \
       scm_bytevector_ ## fn_stem ## _native_set_x (bv, idx, val);       \
     }                                                                   \
+  DEAD (bv);                                                            \
+  DEAD (idx);                                                           \
+  DEAD (val);                                                           \
   NEXT;                                                                 \
 }
 

diff --git a/libguile/vm-i-system.c b/libguile/vm-i-system.c
index 7a7bccc..1e3c2e5 100644 (file)
--- a/libguile/vm-i-system.c
+++ b/libguile/vm-i-system.c
@@ -84,6 +84,7 @@ VM_DEFINE_INSTRUCTION (3, dup, "dup", 0, 0, 1)
 {
   SCM x = *sp;
   PUSH (x);
+  DEAD (x);
   NEXT;
 }
 
@@ -226,6 +227,7 @@ VM_DEFINE_INSTRUCTION (18, vector, "vector", 2, -1, 1)
   memcpy (SCM_I_VECTOR_WELTS(vect), sp, sizeof(SCM) * len);
   NULLSTACK (len);
   *sp = vect;
+  DEAD (vect);
 
   NEXT;
 }
@@ -330,6 +332,7 @@ VM_DEFINE_INSTRUCTION (25, variable_ref, "variable-ref", 0, 1, 1)
     {
       SCM o = VARIABLE_REF (x);
       *sp = o;
+      DEAD (o);
     }
 
   NEXT;
@@ -347,18 +350,20 @@ VM_DEFINE_INSTRUCTION (26, variable_bound, "variable-bound?", 0, 1, 1)
     }
   else
     *sp = scm_from_bool (VARIABLE_BOUNDP (x));
+  DEAD (x);
   NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (27, toplevel_ref, "toplevel-ref", 1, 0, 1)
 {
   unsigned objnum = FETCH ();
-  SCM what, resolved;
+  SCM what;
   CHECK_OBJECT (objnum);
   what = OBJECT_REF (objnum);
 
   if (!SCM_VARIABLEP (what))
     {
+      SCM resolved;
       SYNC_REGISTER ();
       resolved = resolve_variable (what, scm_program_module (program));
       if (!VARIABLE_BOUNDP (resolved))
@@ -367,16 +372,18 @@ VM_DEFINE_INSTRUCTION (27, toplevel_ref, "toplevel-ref", 1, 0, 1)
           goto vm_error_unbound;
         }
       what = resolved;
+      DEAD (resolved);
       OBJECT_SET (objnum, what);
     }
 
   PUSH (VARIABLE_REF (what));
+  DEAD (what);
   NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (28, long_toplevel_ref, "long-toplevel-ref", 2, 0, 1)
 {
-  SCM what, resolved;
+  SCM what;
   unsigned int objnum = FETCH ();
   objnum <<= 8;
   objnum += FETCH ();
@@ -385,6 +392,7 @@ VM_DEFINE_INSTRUCTION (28, long_toplevel_ref, "long-toplevel-ref", 2, 0, 1)
 
   if (!SCM_VARIABLEP (what))
     {
+      SCM resolved;
       SYNC_REGISTER ();
       resolved = resolve_variable (what, scm_program_module (program));
       if (!VARIABLE_BOUNDP (resolved))
@@ -393,10 +401,12 @@ VM_DEFINE_INSTRUCTION (28, long_toplevel_ref, "long-toplevel-ref", 2, 0, 1)
           goto vm_error_unbound;
         }
       what = resolved;
+      DEAD (resolved);
       OBJECT_SET (objnum, what);
     }
 
   PUSH (VARIABLE_REF (what));
+  DEAD (what);
   NEXT;
 }
 
@@ -407,6 +417,7 @@ VM_DEFINE_INSTRUCTION (29, local_set, "local-set", 1, 1, 0)
   SCM x;
   POP (x);
   LOCAL_SET (FETCH (), x);
+  DEAD (x);
   NEXT;
 }
 
@@ -418,6 +429,7 @@ VM_DEFINE_INSTRUCTION (30, long_local_set, "long-local-set", 2, 1, 0)
   i += FETCH ();
   POP (x);
   LOCAL_SET (i, x);
+  DEAD (x);
   NEXT;
 }
 
@@ -449,6 +461,7 @@ VM_DEFINE_INSTRUCTION (32, toplevel_set, "toplevel-set", 1, 1, 0)
     }
 
   VARIABLE_SET (what, *sp);
+  DEAD (what);
   DROP ();
   NEXT;
 }
@@ -470,6 +483,7 @@ VM_DEFINE_INSTRUCTION (33, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
     }
 
   VARIABLE_SET (what, *sp);
+  DEAD (what);
   DROP ();
   NEXT;
 }
@@ -496,7 +510,6 @@ VM_DEFINE_INSTRUCTION (33, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
     ip += offset;                               \
   if (offset < 0)                               \
     VM_HANDLE_INTERRUPTS;                       \
-  NEXT;                                                \
 }
 
 VM_DEFINE_INSTRUCTION (34, br, "br", 3, 0, 0)
@@ -514,6 +527,8 @@ VM_DEFINE_INSTRUCTION (35, br_if, "br-if", 3, 0, 0)
   SCM x;
   POP (x);
   BR (scm_is_true (x));
+  DEAD (x);
+  NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (36, br_if_not, "br-if-not", 3, 0, 0)
@@ -521,6 +536,8 @@ VM_DEFINE_INSTRUCTION (36, br_if_not, "br-if-not", 3, 0, 0)
   SCM x;
   POP (x);
   BR (scm_is_false (x));
+  DEAD (x);
+  NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (37, br_if_eq, "br-if-eq", 3, 0, 0)
@@ -528,6 +545,9 @@ VM_DEFINE_INSTRUCTION (37, br_if_eq, "br-if-eq", 3, 0, 0)
   SCM x, y;
   POP2 (y, x);
   BR (scm_is_eq (x, y));
+  DEAD (x);
+  DEAD (y);
+  NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (38, br_if_not_eq, "br-if-not-eq", 3, 0, 0)
@@ -535,6 +555,9 @@ VM_DEFINE_INSTRUCTION (38, br_if_not_eq, "br-if-not-eq", 3, 0, 0)
   SCM x, y;
   POP2 (y, x);
   BR (!scm_is_eq (x, y));
+  DEAD (x);
+  DEAD (y);
+  NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (39, br_if_null, "br-if-null", 3, 0, 0)
@@ -542,6 +565,8 @@ VM_DEFINE_INSTRUCTION (39, br_if_null, "br-if-null", 3, 0, 0)
   SCM x;
   POP (x);
   BR (scm_is_null (x));
+  DEAD (x);
+  NEXT;
 }
 
 VM_DEFINE_INSTRUCTION (40, br_if_not_null, "br-if-not-null", 3, 0, 0)
@@ -549,6 +574,8 @@ VM_DEFINE_INSTRUCTION (40, br_if_not_null, "br-if-not-null", 3, 0, 0)
   SCM x;
   POP (x);
   BR (!scm_is_null (x));
+  DEAD (x);
+  NEXT;
 }
 
 \f
@@ -712,6 +739,8 @@ VM_DEFINE_INSTRUCTION (48, bind_kwargs, "bind-kwargs", 5, 0, 0)
         goto vm_error_kwargs_invalid_keyword;
     }
 
+  DEAD (kw);
+
   NEXT;
 }
 
@@ -729,6 +758,7 @@ VM_DEFINE_INSTRUCTION (49, push_rest, "push-rest", 2, -1, -1)
     /* No need to check for underflow. */
     CONS (rest, *sp--, rest);
   PUSH (rest);
+  DEAD (rest);
   NEXT;
 }
 
@@ -745,6 +775,7 @@ VM_DEFINE_INSTRUCTION (50, bind_rest, "bind-rest", 4, -1, -1)
     /* No need to check for underflow. */
     CONS (rest, *sp--, rest);
   LOCAL_SET (i, rest);
+  DEAD (rest);
   NEXT;
 }
 
@@ -935,6 +966,7 @@ VM_DEFINE_INSTRUCTION (55, subr_call, "subr-call", 1, -1, -1)
       abort ();
     }
   
+  DEAD (pointer);
   NULLSTACK_FOR_NONLOCAL_EXIT ();
       
   if (SCM_UNLIKELY (SCM_VALUESP (ret)))
@@ -943,11 +975,13 @@ VM_DEFINE_INSTRUCTION (55, subr_call, "subr-call", 1, -1, -1)
       ret = scm_struct_ref (ret, SCM_INUM0);
       nvalues = scm_ilength (ret);
       PUSH_LIST (ret, scm_is_null);
+      DEAD (ret);
       goto vm_return_values;
     }
   else
     {
       PUSH (ret);
+      DEAD (ret);
       goto vm_return;
     }
 }
@@ -982,6 +1016,7 @@ VM_DEFINE_INSTRUCTION (56, smob_call, "smob-call", 1, -1, -1)
       abort ();
     }
   
+  DEAD (smob);
   NULLSTACK_FOR_NONLOCAL_EXIT ();
       
   if (SCM_UNLIKELY (SCM_VALUESP (ret)))
@@ -990,11 +1025,13 @@ VM_DEFINE_INSTRUCTION (56, smob_call, "smob-call", 1, -1, -1)
       ret = scm_struct_ref (ret, SCM_INUM0);
       nvalues = scm_ilength (ret);
       PUSH_LIST (ret, scm_is_null);
+      DEAD (ret);
       goto vm_return_values;
     }
   else
     {
       PUSH (ret);
+      DEAD (ret);
       goto vm_return;
     }
 }
@@ -1010,6 +1047,7 @@ VM_DEFINE_INSTRUCTION (57, foreign_call, "foreign-call", 1, -1, -1)
 
   ret = scm_i_foreign_call (foreign, sp - nargs + 1);
 
+  DEAD (foreign);
   NULLSTACK_FOR_NONLOCAL_EXIT ();
       
   if (SCM_UNLIKELY (SCM_VALUESP (ret)))
@@ -1018,11 +1056,13 @@ VM_DEFINE_INSTRUCTION (57, foreign_call, "foreign-call", 1, -1, -1)
       ret = scm_struct_ref (ret, SCM_INUM0);
       nvalues = scm_ilength (ret);
       PUSH_LIST (ret, scm_is_null);
+      DEAD (ret);
       goto vm_return_values;
     }
   else
     {
       PUSH (ret);
+      DEAD (ret);
       goto vm_return;
     }
 }
@@ -1039,7 +1079,7 @@ VM_DEFINE_INSTRUCTION (58, continuation_call, "continuation-call", 0, -1, 0)
                              sp - (fp - 1), fp);
   scm_i_reinstate_continuation (contregs);
 
-  /* no NEXT */
+  /* no DEAD, no NEXT */
   abort ();
 }
 
@@ -1049,12 +1089,15 @@ VM_DEFINE_INSTRUCTION (59, partial_cont_call, "partial-cont-call", 0, -1, 0)
   POP2 (intwinds, vmcont);
   SYNC_REGISTER ();
   if (SCM_UNLIKELY (!SCM_VM_CONT_REWINDABLE_P (vmcont)))
-    { finish_args = vmcont;
+    {
+      finish_args = vmcont;
       goto vm_error_continuation_not_rewindable;
     }
   prevwinds = scm_i_dynwinds ();
   vm_reinstate_partial_continuation (vm, vmcont, intwinds, sp + 1 - fp, fp,
                                      vm_cookie);
+  DEAD (vmcont);
+  DEAD (intwinds);
 
   /* Rewind prompt jmpbuffers, if any. */
   {
@@ -1062,7 +1105,9 @@ VM_DEFINE_INSTRUCTION (59, partial_cont_call, "partial-cont-call", 0, -1, 0)
     for (; !scm_is_eq (winds, prevwinds); winds = scm_cdr (winds))
       if (SCM_PROMPT_P (scm_car (winds)) && SCM_PROMPT_SETJMP (scm_car (winds)))
         break;
+    DEAD (winds);
   }
+  DEAD (prevwinds);
     
   CACHE_REGISTER ();
   program = SCM_FRAME_PROGRAM (fp);
@@ -1075,6 +1120,7 @@ VM_DEFINE_INSTRUCTION (60, tail_call_nargs, "tail-call/nargs", 0, 0, 1)
   SCM x;
   POP (x);
   nargs = scm_to_int (x);
+  DEAD (x);
   /* FIXME: should truncate values? */
   goto vm_tail_call;
 }
@@ -1084,6 +1130,7 @@ VM_DEFINE_INSTRUCTION (61, call_nargs, "call/nargs", 0, 0, 1)
   SCM x;
   POP (x);
   nargs = scm_to_int (x);
+  DEAD (x);
   /* FIXME: should truncate values? */
   goto vm_call;
 }
@@ -1158,6 +1205,7 @@ VM_DEFINE_INSTRUCTION (63, apply, "apply", 1, -1, 1)
     }
 
   PUSH_LIST (ls, SCM_NULL_OR_NIL_P);
+  DEAD (ls);
 
   nargs += len - 2;
   goto vm_call;
@@ -1180,6 +1228,7 @@ VM_DEFINE_INSTRUCTION (64, tail_apply, "tail-apply", 1, -1, 1)
     }
 
   PUSH_LIST (ls, SCM_NULL_OR_NIL_P);
+  DEAD (ls);
 
   nargs += len - 2;
   goto vm_tail_call;
@@ -1193,13 +1242,16 @@ VM_DEFINE_INSTRUCTION (65, call_cc, "call/cc", 0, 1, 1)
   SYNC_ALL ();
   vm_cont = scm_i_vm_capture_stack (vp->stack_base, fp, sp, ip, NULL, 0);
   cont = scm_i_make_continuation (&first, vm, vm_cont);
+  DEAD (vm_cont);
   if (first) 
     {
       PUSH (SCM_PACK (0)); /* dynamic link */
       PUSH (SCM_PACK (0));  /* mvra */
       PUSH (SCM_PACK (0));  /* ra */
       PUSH (proc);
+      DEAD (proc);
       PUSH (cont);
+      DEAD (cont);
       nargs = 1;
       goto vm_call;
     }
@@ -1212,6 +1264,8 @@ VM_DEFINE_INSTRUCTION (65, call_cc, "call/cc", 0, 1, 1)
 
          So, pull our regs back down from the vp, and march on to the
          next instruction. */
+      DEAD (proc);
+      DEAD (cont);
       CACHE_REGISTER ();
       program = SCM_FRAME_PROGRAM (fp);
       CACHE_PROGRAM ();
@@ -1235,15 +1289,20 @@ VM_DEFINE_INSTRUCTION (66, tail_call_cc, "tail-call/cc", 0, 1, 1)
                                     SCM_FRAME_MV_RETURN_ADDRESS (fp),
                                     0);
   cont = scm_i_make_continuation (&first, vm, vm_cont);
+  DEAD (vm_cont);
   if (first) 
     {
       PUSH (proc);
+      DEAD (proc);
       PUSH (cont);
+      DEAD (cont);
       nargs = 1;
       goto vm_tail_call;
     }
   else
     {
+      DEAD (proc);
+      DEAD (cont);
       /* Otherwise, cache regs and NEXT, as above. Invoking the continuation
          does a return from the frame, either to the RA or
          MVRA. */
@@ -1288,6 +1347,8 @@ VM_DEFINE_INSTRUCTION (67, return, "return", 0, 1, 1)
 
     /* Set return value (sp is already pushed) */
     *sp = ret;
+
+    DEAD (ret);
   }
 
   /* Restore the last program */
@@ -1375,6 +1436,7 @@ VM_DEFINE_INSTRUCTION (69, return_values_star, "return/values*", 1, -1, -1)
     goto vm_error_improper_list;
   }
 
+  DEAD (l);
   goto vm_return_values;
 }
 
@@ -1383,6 +1445,7 @@ VM_DEFINE_INSTRUCTION (70, return_nvalues, "return/nvalues", 0, 1, -1)
   SCM n;
   POP (n);
   nvalues = scm_to_int (n);
+  DEAD (n);
   ASSERT (nvalues >= 0);
   goto vm_return_values;
 }
@@ -1393,6 +1456,7 @@ VM_DEFINE_INSTRUCTION (71, truncate_values, "truncate-values", 2, -1, -1)
   int nbinds, rest;
   POP (x);
   nvalues = scm_to_int (x);
+  DEAD (x);
   nbinds = FETCH ();
   rest = FETCH ();
 
@@ -1416,6 +1480,7 @@ VM_DEFINE_INSTRUCTION (72, box, "box", 1, 1, 0)
   POP (val);
   SYNC_BEFORE_GC ();
   LOCAL_SET (FETCH (), scm_cell (scm_tc7_variable, SCM_UNPACK (val)));
+  DEAD (val);
   NEXT;
 }
 
@@ -1437,6 +1502,7 @@ VM_DEFINE_INSTRUCTION (74, local_boxed_ref, "local-boxed-ref", 1, 0, 1)
   SCM v = LOCAL_REF (FETCH ());
   ASSERT_BOUND_VARIABLE (v);
   PUSH (VARIABLE_REF (v));
+  DEAD (v);
   NEXT;
 }
 
@@ -1447,6 +1513,8 @@ VM_DEFINE_INSTRUCTION (75, local_boxed_set, "local-boxed-set", 1, 1, 0)
   POP (val);
   ASSERT_VARIABLE (v);
   VARIABLE_SET (v, val);
+  DEAD (v);
+  DEAD (val);
   NEXT;
 }
 
@@ -1469,6 +1537,7 @@ VM_DEFINE_INSTRUCTION (77, free_boxed_ref, "free-boxed-ref", 1, 0, 1)
   v = FREE_VARIABLE_REF (idx);
   ASSERT_BOUND_VARIABLE (v);
   PUSH (VARIABLE_REF (v));
+  DEAD (v);
   NEXT;
 }
 
@@ -1481,6 +1550,8 @@ VM_DEFINE_INSTRUCTION (78, free_boxed_set, "free-boxed-set", 1, 1, 0)
   v = FREE_VARIABLE_REF (idx);
   ASSERT_BOUND_VARIABLE (v);
   VARIABLE_SET (v, val);
+  DEAD (v);
+  DEAD (val);
   NEXT;
 }
 
@@ -1499,6 +1570,7 @@ VM_DEFINE_INSTRUCTION (79, make_closure, "make-closure", 2, -1, 1)
   sp[-len] = closure;
   for (n = 0; n < len; n++)
     SCM_PROGRAM_FREE_VARIABLE_SET (closure, n, sp[-len + 1 + n]);
+  DEAD (closure);
   DROPN (len);
   NEXT;
 }
@@ -1524,6 +1596,7 @@ VM_DEFINE_INSTRUCTION (81, fix_closure, "fix-closure", 2, -1, 0)
   len = SCM_PROGRAM_NUM_FREE_VARIABLES (x);
   for (n = 0; n < len; n++)
     SCM_PROGRAM_FREE_VARIABLE_SET (x, n, sp[-len + 1 + n]);
+  DEAD (x);
   DROPN (len);
   NEXT;
 }
@@ -1536,6 +1609,8 @@ VM_DEFINE_INSTRUCTION (82, define, "define", 0, 0, 2)
   VARIABLE_SET (scm_sym2var (sym, scm_current_module_lookup_closure (),
                              SCM_BOOL_T),
                 val);
+  DEAD (sym);
+  DEAD (val);
   NEXT;
 }
 
@@ -1579,6 +1654,8 @@ VM_DEFINE_INSTRUCTION (85, prompt, "prompt", 4, 2, 0)
          vm_engine that can be assigned *has* been assigned. So we need to pull
          all our state back from the ip/fp/sp.
       */
+      DEAD (k);
+      DEAD (prompt);
       CACHE_REGISTER ();
       program = SCM_FRAME_PROGRAM (fp);
       CACHE_PROGRAM ();
@@ -1588,6 +1665,9 @@ VM_DEFINE_INSTRUCTION (85, prompt, "prompt", 4, 2, 0)
       NEXT;
     }
       
+  DEAD (k);
+  DEAD (prompt);
+  
   /* Otherwise setjmp returned for the first time, so we go to execute the
      prompt's body. */
   NEXT;
@@ -1612,6 +1692,8 @@ VM_DEFINE_INSTRUCTION (86, wind, "wind", 0, 2, 0)
       goto vm_error_not_a_thunk;
     }
   scm_i_set_dynwinds (scm_cons (scm_cons (wind, unwind), scm_i_dynwinds ()));
+  DEAD (wind);
+  DEAD (unwind);
   NEXT;
 }
 
@@ -1647,6 +1729,7 @@ VM_DEFINE_INSTRUCTION (89, wind_fluids, "wind-fluids", 1, -1, 0)
 
   scm_i_swap_with_fluids (wf, current_thread->dynamic_state);
   scm_i_set_dynwinds (scm_cons (wf, scm_i_dynwinds ()));
+  DEAD (wf);
   NEXT;
 }
 
@@ -1656,6 +1739,7 @@ VM_DEFINE_INSTRUCTION (90, unwind_fluids, "unwind-fluids", 0, 0, 0)
   wf = scm_car (scm_i_dynwinds ());
   scm_i_set_dynwinds (scm_cdr (scm_i_dynwinds ()));
   scm_i_swap_with_fluids (wf, current_thread->dynamic_state);
+  DEAD (wf);
   NEXT;
 }
 
@@ -1670,12 +1754,14 @@ VM_DEFINE_INSTRUCTION (91, fluid_ref, "fluid-ref", 0, 1, 1)
       || ((num = SCM_I_FLUID_NUM (*sp)) >= SCM_SIMPLE_VECTOR_LENGTH (fluids)))
     {
       /* Punt dynstate expansion and error handling to the C proc. */
+      DEAD (fluids);
       SYNC_REGISTER ();
       *sp = scm_fluid_ref (*sp);
     }
   else
     {
       SCM val = SCM_SIMPLE_VECTOR_REF (fluids, num);
+      DEAD (fluids);
       if (scm_is_eq (val, SCM_UNDEFINED))
         val = SCM_I_FLUID_DEFAULT (*sp);
       if (SCM_UNLIKELY (scm_is_eq (val, SCM_UNDEFINED)))
@@ -1705,7 +1791,9 @@ VM_DEFINE_INSTRUCTION (92, fluid_set, "fluid-set", 0, 2, 0)
     }
   else
     SCM_SIMPLE_VECTOR_SET (fluids, num, val);
-  
+  DEAD (fluids);
+  DEAD (fluid);
+  DEAD (val);
   NEXT;
 }