fix error handling in variable-ref family of instructions

* libguile/vm-i-system.c (variable-ref, variable-set, variable-bound?):
  Check that the argument is actually a variable.  Thanks to Kevin
  Holmes for the report.

* libguile/vm-engine.c (vm_engine): Error handling down here.

* THANKS: Update.

THANKS

@@ -63,6 +63,7 @@ For fixes or providing information which led to a fix:
 	   Judy Hawkins
 	    Jon Herron
             Sam Hocevar
+          Kevin Holmnes
 	Patrick Horgan
            Ales Hvezda
          Stefan Israelsson Tampe

libguile/vm-engine.c

@@ -153,6 +153,12 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
                    scm_list_1 (finish_args), SCM_BOOL_F);
     goto vm_error;
 
+  vm_error_not_a_variable:
+    SYNC_ALL ();
+    scm_error (scm_arg_type_key, func_name, "Not a variable: ~S",
+               scm_list_1 (finish_args), scm_list_1 (finish_args));
+    goto vm_error;
+
   vm_error_apply_to_non_list:
     SYNC_ALL ();
     scm_error (scm_arg_type_key, "apply", "Apply to non-list: ~S",

libguile/vm-i-system.c

@@ -1,4 +1,4 @@
-/* Copyright (C) 2001,2008,2009,2010 Free Software Foundation, Inc.
+/* Copyright (C) 2001,2008,2009,2010,2011 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
@@ -300,7 +300,17 @@ VM_DEFINE_INSTRUCTION (25, variable_ref, "variable-ref", 0, 1, 1)
 {
   SCM x = *sp;
 
-  if (SCM_UNLIKELY (!VARIABLE_BOUNDP (x)))
+  /* We don't use ASSERT_VARIABLE or ASSERT_BOUND_VARIABLE here because,
+     unlike in top-variable-ref, it really isn't an internal assertion
+     that can be optimized out -- the variable could be coming directly
+     from the user.  */
+  if (SCM_UNLIKELY (!SCM_VARIABLEP (x)))
+    {
+      func_name = "variable-ref";
+      finish_args = x;
+      goto vm_error_not_a_variable;
+    }
+  else if (SCM_UNLIKELY (!VARIABLE_BOUNDP (x)))
     {
       SCM var_name;
 
@@ -320,10 +330,16 @@ VM_DEFINE_INSTRUCTION (25, variable_ref, "variable-ref", 0, 1, 1)
 
 VM_DEFINE_INSTRUCTION (26, variable_bound, "variable-bound?", 0, 1, 1)
 {
-  if (VARIABLE_BOUNDP (*sp))
+  SCM x = *sp;
-    *sp = SCM_BOOL_T;
+  
+  if (SCM_UNLIKELY (!SCM_VARIABLEP (x)))
+    {
+      func_name = "variable-bound?";
+      finish_args = x;
+      goto vm_error_not_a_variable;
+    }
   else
-    *sp = SCM_BOOL_F;
+    *sp = scm_from_bool (VARIABLE_BOUNDP (x));
   NEXT;
 }
 
@@ -398,6 +414,12 @@ VM_DEFINE_INSTRUCTION (30, long_local_set, "long-local-set", 2, 1, 0)
 
 VM_DEFINE_INSTRUCTION (31, variable_set, "variable-set", 0, 2, 0)
 {
+  if (SCM_UNLIKELY (!SCM_VARIABLEP (sp[0])))
+    {
+      func_name = "variable-set!";
+      finish_args = sp[0];
+      goto vm_error_not_a_variable;
+    }
   VARIABLE_SET (sp[0], sp[-1]);
   DROPN (2);
   NEXT;