8332461: ubsan : dependencies.cpp:906:3: runtime error: load of value 4294967295, which is not a valid value for type 'DepType'

Reviewed-by: stefank, kvn, dlong

src/hotspot/share/code/dependencies.cpp

@@ -893,7 +893,7 @@ void Dependencies::DepStream::print_dependency(outputStream* st, Klass* witness,
 void Dependencies::DepStream::initial_asserts(size_t byte_limit) {
   assert(must_be_in_vm(), "raw oops here");
   _byte_limit = byte_limit;
-  _type       = (DepType)(end_marker-1);  // defeat "already at end" assert
+  _type       = undefined_dependency;  // defeat "already at end" assert
   assert((_code!=nullptr) + (_deps!=nullptr) == 1, "one or t'other");
 }
 #endif //ASSERT

src/hotspot/share/code/dependencies.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2024, 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
@@ -103,6 +103,9 @@ class Dependencies: public ResourceObj {
   // type now includes N, that is, all super types of N.
   //
   enum DepType {
+    // _type is initially set to -1, to prevent "already at end" assert
+    undefined_dependency = -1,
+
     end_marker = 0,
 
     // An 'evol' dependency simply notes that the contents of the