Fixed debugger stacktrace generation that failed a VM assertion.

runtime/vm/object.cc

 // Copyright (c) 2012, 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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 7062 matching lines @@
 
 
 void LocalVarDescriptors::GetInfo(intptr_t var_index,
                                   RawLocalVarDescriptors::VarInfo* info) const {
   ASSERT(var_index < Length());
   *info = raw_ptr()->data_[var_index];
 }
 
 
 const char* LocalVarDescriptors::ToCString() const {
-  UNIMPLEMENTED();
-  return "LocalVarDescriptors";
+  intptr_t len = 1;  // Trailing '\0'.
+  const char* kFormat =
+      "%2"Pd" kind=%d scope=0x%04x begin=%"Pd" end=%"Pd" name=%s\n";
+  for (intptr_t i = 0; i < Length(); i++) {
+    String& var_name = String::Handle(GetName(i));
+    RawLocalVarDescriptors::VarInfo info;
+    GetInfo(i, &info);
+    len += OS::SNPrint(NULL, 0, kFormat,
+                       i,
+                       info.kind,
+                       info.scope_id,
+                       info.begin_pos,
+                       info.end_pos,
+                       var_name.ToCString());
+  }
+  char* buffer = Isolate::Current()->current_zone()->Alloc<char>(len);
+  intptr_t num_chars = 0;
+  for (intptr_t i = 0; i < Length(); i++) {
+    String& var_name = String::Handle(GetName(i));
+    RawLocalVarDescriptors::VarInfo info;
+    GetInfo(i, &info);
+    num_chars += OS::SNPrint((buffer + num_chars),
+                             (len - num_chars),
+                             kFormat,
+                             i,
+                             info.kind,
+                             info.scope_id,
+                             info.begin_pos,
+                             info.end_pos,
+                             var_name.ToCString());
+  }
+  return buffer;
 }
 
 
 RawLocalVarDescriptors* LocalVarDescriptors::New(intptr_t num_variables) {
   ASSERT(Object::var_descriptors_class() != Class::null());
   if (num_variables < 0 || num_variables > kMaxElements) {
     // This should be caught before we reach here.
     FATAL1("Fatal error in LocalVarDescriptors::New: "
            "invalid num_variables %"Pd"\n", num_variables);
   }
@@ skipping 6065 matching lines @@
   }
   return result.raw();
 }
 
 
 const char* WeakProperty::ToCString() const {
   return "_WeakProperty";
 }
 
 }  // namespace dart