Save the entry context for a function that has captured loop variables.

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/cpu.h"
@@ skipping 10291 matching lines @@
                        info.scope_id,
                        info.index,
                        info.begin_pos,
                        info.end_pos,
                        var_name.ToCString());
   }
 }
 
 
 const char* LocalVarDescriptors::ToCString() const {
+  if (IsNull()) {
+    return "LocalVarDescriptors(NULL)";
+  }
   intptr_t len = 1;  // Trailing '\0'.
   String& var_name = String::Handle();
   for (intptr_t i = 0; i < Length(); i++) {
     RawLocalVarDescriptors::VarInfo info;
     var_name = GetName(i);
     if (var_name.IsNull()) {
       var_name = Symbols::Empty().raw();
     }
     GetInfo(i, &info);
     len += PrintVarInfo(NULL, 0, i, var_name, info);
   }
-  char* buffer = Isolate::Current()->current_zone()->Alloc<char>(len);
+  char* buffer = Isolate::Current()->current_zone()->Alloc<char>(len + 1);
+  buffer[0] = '\0';
   intptr_t num_chars = 0;
   for (intptr_t i = 0; i < Length(); i++) {
     RawLocalVarDescriptors::VarInfo info;
     var_name = GetName(i);
     if (var_name.IsNull()) {
       var_name = Symbols::Empty().raw();
     }
     GetInfo(i, &info);
     num_chars += PrintVarInfo((buffer + num_chars),
                               (len - num_chars),
@@ skipping 8386 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart