Fix crash in x64: handler's pc-offset must be in 32-bit uword range

runtime/vm/code_descriptors.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/code_descriptors.h"
 
 namespace dart {
 
 void DescriptorList::AddDescriptor(RawPcDescriptors::Kind kind,
                                    intptr_t pc_offset,
@@ skipping 81 matching lines @@
     return Object::empty_exception_handlers().raw();
   }
   const ExceptionHandlers& handlers =
       ExceptionHandlers::Handle(ExceptionHandlers::New(num_handlers));
   for (intptr_t i = 0; i < num_handlers; i++) {
     // Assert that every element in the array has been initialized.
     if (list_[i].handler_types == NULL) {
       // Unreachable handler, entry not computed.
       // Initialize it to some meaningful value.
       const bool has_catch_all = false;
+      // Check it is uninitialized.
       ASSERT((list_[i].outer_try_index == -1) &&
-             (list_[i].pc_offset == -1));  // It is uninitialized.
+             (list_[i].pc_offset == ExceptionHandlers::kInvalidPcOffset));
       handlers.SetHandlerInfo(i,
                               list_[i].outer_try_index,
                               list_[i].pc_offset,
                               list_[i].needs_stacktrace,
                               has_catch_all);
       handlers.SetHandledTypes(i, Array::null_array());
     } else {
       const bool has_catch_all = ContainsDynamic(*list_[i].handler_types);
       handlers.SetHandlerInfo(i,
                               list_[i].outer_try_index,
                               list_[i].pc_offset,
                               list_[i].needs_stacktrace,
                               has_catch_all);
       handlers.SetHandledTypes(i, *list_[i].handler_types);
     }
   }
   return handlers.raw();
 }
 
 
 }  // namespace dart