Getting value of local variables on stack trace

runtime/vm/scopes.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/scopes.h"
 
 #include "vm/ast.h"
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 155 matching lines @@
     if ((child_context_owner != *context_owner) &&
         (child_context_owner->loop_level() <= loop_owner->loop_level())) {
       *context_owner = child_context_owner;
     }
     child = child->sibling();
   }
   return min_frame_index;
 }
 
 
-static int CompareVariableRanges(
-    LocalVariable* const* a, LocalVariable* const* b) {
-  if ((*a)->token_index() < (*b)->token_index()) return -1;
-  if ((*a)->token_index() > (*b)->token_index()) return 1;
-  return 0;
-}
-
-
 RawLocalVarDescriptors* LocalScope::GetVarDescriptors() {
   GrowableArray<LocalVariable*> vars(8);
   CollectLocalVariables(&vars);
-  vars.Sort(&CompareVariableRanges);
   const LocalVarDescriptors& var_desc =
       LocalVarDescriptors::Handle(LocalVarDescriptors::New(vars.length()));
+  intptr_t scope_id = -1;
+  LocalScope* current_scope = NULL;
   for (int i = 0;  i < vars.length(); i++) {
     LocalVariable* var = vars[i];
+    if (current_scope != var->owner()) {
+      current_scope = var->owner();
+      scope_id += 1;
+    }

[siva, 2012/01/05 02:01:45]

This seems kind of fragile as it assumes that all the variables in a scope will
be consecutive in 'vars'.
Why not add a scope_id field to LocalScope and assign a scope_id value when a
new LocalScope is created. 

[hausner, 2012/01/05 22:33:21]

True. CollectLocalVariables() function below makes sure that all variables of a
scope are consecutive in the vars array. Added a comment to describe this.

The nice thing about this solution (rather than generating scope ids globally)
is that the parameters are always in scope 0. Also, we don't have to maintain a
global id counter (or add one to the isolate).

     var_desc.SetVar(i, var->name(), var->index(),
-        var->token_index(), var->owner()->end_token_index());
+        scope_id, var->token_index(), var->owner()->end_token_index());
   }
   return var_desc.raw();
 }
 
 
 void LocalScope::CollectLocalVariables(GrowableArray<LocalVariable*>* vars) {
   for (int i = 0; i < this->variables_.length(); i++) {
     LocalVariable* var = variables_[i];
     if ((var->owner() == this) && Scanner::IsIdent(var->name())) {
       vars->Add(this->variables_[i]);
@@ skipping 255 matching lines @@
       }
       if (owner()->context_level() == other.owner()->context_level()) {
         return true;
       }
     }
   }
   return false;
 }
 
 }  // namespace dart