diff -r 6ce4101edc7a -r da2e98c027fd src/share/vm/asm/assembler.hpp
--- a/src/share/vm/asm/assembler.hpp	Thu Dec 06 13:26:54 2018 -0500
+++ b/src/share/vm/asm/assembler.hpp	Thu Dec 20 20:11:38 2018 +0000
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -169,6 +169,14 @@
   Label() {
     init();
   }
+
+  ~Label() {
+    assert(is_bound() || is_unused(), "Label was never bound to a location, but it was used as a jmp target");
+  }
+
+  void reset() {
+    init(); //leave _patch_overflow because it points to CodeBuffer.
+  }
 };
 
 // A union type for code which has to assemble both constant and