Fix TryCatch.ReThrow() to not clobber Message.

src/isolate.cc

Index: src/isolate.cc
===================================================================
--- src/isolate.cc	(revision 14909)
+++ src/isolate.cc	(working copy)
@@ -107,6 +107,7 @@
   // is complete.
   pending_exception_ = NULL;
   has_pending_message_ = false;
+  restoring_message_ = false;
   pending_message_obj_ = NULL;
   pending_message_script_ = NULL;
   scheduled_exception_ = NULL;
@@ -480,7 +481,8 @@
        block != NULL;
        block = TRY_CATCH_FROM_ADDRESS(block->next_)) {
     v->VisitPointer(BitCast<Object**>(&(block->exception_)));
-    v->VisitPointer(BitCast<Object**>(&(block->message_)));
+    v->VisitPointer(BitCast<Object**>(&(block->message_obj_)));
+    v->VisitPointer(BitCast<Object**>(&(block->message_script_)));
   }
 
   // Iterate over pointers on native execution stack.
@@ -1156,6 +1158,19 @@
 }
 
 
+void Isolate::RestoreMessage(Object* message, Script* script,
+                             int start_pos, int end_pos) {
+  // Flag is checked in DoThrow(), which immediately follows.
+  thread_local_top()->restoring_message_ = true;
+  thread_local_top()->pending_message_obj_ = message;
+  if (script) {
+    thread_local_top()->pending_message_script_ = script;
+  }
+  thread_local_top()->pending_message_start_pos_ = start_pos;
+  thread_local_top()->pending_message_end_pos_ = end_pos;
+}
+
+
 Failure* Isolate::PromoteScheduledException() {
   MaybeObject* thrown = scheduled_exception();
   clear_scheduled_exception();
@@ -1273,10 +1288,18 @@
   bool should_report_exception =
       ShouldReportException(&can_be_caught_externally, catchable_by_javascript);
   bool report_exception = catchable_by_javascript && should_report_exception;
+  // When determining if a message needs to be generated, make sure to check
+  // restoring_message_.  If an external TryCatch re-threw an exception, it
+  // will have already called RestoreMessage() to put the original message,
+  // script, and location back in place.  In that case, this code must not
+  // clobber the values computed from the original exception.
   bool try_catch_needs_message =
-      can_be_caught_externally && try_catch_handler()->capture_message_;
+      can_be_caught_externally && try_catch_handler()->capture_message_ &&
+      !thread_local_top_.restoring_message_;
   bool bootstrapping = bootstrapper()->IsActive();
 
+  thread_local_top_.restoring_message_ = false;
+
 #ifdef ENABLE_DEBUGGER_SUPPORT
   // Notify debugger of exception.
   if (catchable_by_javascript) {
@@ -2041,7 +2064,16 @@
     try_catch_handler()->has_terminated_ = false;
     try_catch_handler()->exception_ = pending_exception();
     if (!thread_local_top_.pending_message_obj_->IsTheHole()) {
-      try_catch_handler()->message_ = thread_local_top_.pending_message_obj_;
+      try_catch_handler()->message_obj_ =
+        thread_local_top_.pending_message_obj_;
+      if (!thread_local_top_.pending_message_script_->IsTheHole()) {
+        try_catch_handler()->message_script_ =
+          thread_local_top_.pending_message_script_;
+      }
+      try_catch_handler()->message_start_pos_ =
+        thread_local_top_.pending_message_start_pos_;
+      try_catch_handler()->message_end_pos_ =
+        thread_local_top_.pending_message_end_pos_;
     }
   }
 }