Propagate UnhandledExceptionErrors returned by the tag handler in Reload

runtime/vm/isolate_reload.cc

 // Copyright (c) 2016, 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/isolate_reload.h"
 
 #include "vm/become.h"
 #include "vm/bit_vector.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 472 matching lines @@
   //   1) Tag Handler is invoked and the embedder is in control.
   //   2) All sources and libraries are loaded.
   //   3) Dart_FinalizeLoading is called by the embedder.
   //   4) Dart_FinalizeLoading invokes IsolateReloadContext::FinalizeLoading
   //      and we are temporarily back in control.
   //      This is where we validate the reload and commit or reject.
   //   5) Dart_FinalizeLoading invokes Dart code related to deferred libraries.
   //   6) The tag handler returns and we move on.
   //
   // Even after a successful reload the Dart code invoked in (5) can result
-  // in an Unwind error or a StackOverflow error. This error will be returned
-  // by the tag handler. The tag handler can return other errors, for example,
-  // top level parse errors. We want to capture these errors while propagating
-  // the Unwind or StackOverflow errors.
+  // in an Unwind error or an UnhandledException error. This error will be
+  // returned by the tag handler. The tag handler can return other errors,
+  // for example, top level parse errors. We want to capture these errors while
+  // propagating the UnwindError or an UnhandledException error.
   Object& result = Object::Handle(thread->zone());
   {
     TransitionVMToNative transition(thread);
     Api::Scope api_scope(thread);
 
     Dart_Handle retval =
         (I->library_tag_handler())(Dart_kScriptTag,
                                    Api::NewHandle(thread, Library::null()),
                                    Api::NewHandle(thread, root_lib_url.raw()));
     result = Api::UnwrapHandle(retval);
   }
   //
   // WEIRD CONTROL FLOW ENDS.
 
   BackgroundCompiler::Enable();
 
   if (result.IsUnwindError() ||
-      (result.raw() == isolate()->object_store()->stack_overflow())) {
-    // When returning from the tag handler with an Unwind error or a
-    // StackOverflow error, propagate it and give up.
+      result.IsUnhandledException()) {
+    // If the tag handler returns with an UnwindError or an UnhandledException
+    // error, propagate it and give up.
     Exceptions::PropagateError(Error::Cast(result));
     UNREACHABLE();
   }
 
   // Other errors (e.g. a parse error) are captured by the reload system.
   if (result.IsError()) {
     FinalizeFailedLoad(Error::Cast(result));
   }
 }
 
@@ skipping 1117 matching lines @@
         ASSERT(!super_cls.IsNull());
         super_cls.AddDirectSubclass(cls);
       }
     }
   }
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart