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);
+  // Variables of each scope are guaranteed to be consecutive elements
+  // in array vars. See CollectLocalVariables() below. The outermost
+  // scope (containing the function parameters) has id 0.
   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;
+    }
     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();
 }
 
 
+// Add variables that are declared in this scope to vars, then collect
+// variables of children, followed by siblings.
 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]);
     }
   }
   if (child() != NULL) {
     child()->CollectLocalVariables(vars);
   }
@@ skipping 250 matching lines @@
       }
       if (owner()->context_level() == other.owner()->context_level()) {
         return true;
       }
     }
   }
   return false;
 }
 
 }  // namespace dart