--- old/src/share/vm/asm/codeBuffer.hpp	2014-08-22 16:43:38.774491794 -0400
+++ new/src/share/vm/asm/codeBuffer.hpp	2014-08-22 16:43:38.702489235 -0400
@@ -27,6 +27,7 @@
 
 #include "code/oopRecorder.hpp"
 #include "code/relocInfo.hpp"
+#include "utilities/debug.hpp"
 
 class CodeStrings;
 class PhaseCFG;
@@ -245,15 +246,33 @@
 private:
 #ifndef PRODUCT
   CodeString* _strings;
+  // Becomes true after copy-out, forbids further use.
+  bool _defunct; // Zero bit pattern is "valid", see memset call in decode_env::decode_env
 #endif
 
   CodeString* find(intptr_t offset) const;
   CodeString* find_last(intptr_t offset) const;
 
+  void set_null_and_invalidate() {
+#ifdef ASSERT
+    _strings = NULL;
+    _defunct = true;
+#endif
+  }
+
 public:
   CodeStrings() {
 #ifndef PRODUCT
     _strings = NULL;
+    _defunct = false;
+#endif
+  }
+
+  bool isNull() {
+#ifdef ASSERT
+    return _strings == NULL;
+#else
+    return true;
 #endif
   }
 
@@ -261,8 +280,17 @@
 
   void add_comment(intptr_t offset, const char * comment) PRODUCT_RETURN;
   void print_block_comment(outputStream* stream, intptr_t offset) const PRODUCT_RETURN;
+  // MOVE strings from other to this; invalidate other.
   void assign(CodeStrings& other)  PRODUCT_RETURN;
+  // COPY strings from other to this; leave other valid.
+  void copy(CodeStrings& other)  PRODUCT_RETURN;
   void free() PRODUCT_RETURN;
+  // Guarantee that _strings are used at most once; assign invalidates a buffer.
+  inline void check_valid() const {
+#ifdef ASSERT
+    assert(!_defunct, "Use of invalid CodeStrings");
+#endif
+  }
 };
 
 // A CodeBuffer describes a memory space into which assembly
@@ -533,6 +561,12 @@
   OopRecorder* oop_recorder() const   { return _oop_recorder; }
   CodeStrings& strings()              { return _strings; }
 
+  void free_strings() {
+    if (!_strings.isNull()) {
+      _strings.free(); // sets _strings Null as a side-effect.
+    }
+  }
+
   // Code generation
   void relocate(address at, RelocationHolder const& rspec, int format = 0) {
     _insts.relocate(at, rspec, format);