[2096] (Unrelated) MessageRenderer isn't copyable

Discovered the hard way - it can crash.

Small trick with just-in-time initialization of a pointer in benchmark
is used instead of copying it and relying on the fact that it can be
copied while it was not yet used.

src/lib/dns/benchmarks/message_renderer_bench.cc

@@ -35,21 +35,28 @@ template <typename T>
 class MessageRendererBenchMark {
 public:
     MessageRendererBenchMark(const vector<Name>& names) :
+        renderer_(NULL),
         names_(names)
     {}
+    MessageRendererBenchMark() {
+        delete renderer_;
+    }
     unsigned int run() {
-        renderer_.clear();
+        if (renderer_ == NULL) {
+            renderer_ = new T();
+        }
+        renderer_->clear();
         vector<Name>::const_iterator it = names_.begin();
         const vector<Name>::const_iterator it_end = names_.end();
         for (; it != it_end; ++it) {
-            renderer_.writeName(*it);
+            renderer_->writeName(*it);
         }
         // Make sure truncation didn't accidentally happen.
-        assert(!renderer_.isTruncated());
+        assert(!renderer_->isTruncated());
         return (names_.size());
     }
 private:
-    T renderer_;
+    T* renderer_; // It's pointer, so we won't need to copy it.
     const vector<Name>& names_;
 };
 

src/lib/dns/benchmarks/rdatarender_bench.cc

@@ -44,18 +44,25 @@ public:
     RdataRenderBenchMark(const vector<T>& dataset) :
         dataset_(dataset)
     {}
+    RdataRenderBenchMark() {
+        delete renderer_;
+    }
     unsigned int run() {
+        if (renderer_ == NULL) {
+            renderer_ = new MessageRenderer();
+        }
         typename vector<T>::const_iterator data;
         typename vector<T>::const_iterator data_end = dataset_.end();
         for (data = dataset_.begin(); data != data_end; ++data) {
-            renderer_.clear();
-            (*data)->toWire(renderer_);
+            renderer_->clear();
+            (*data)->toWire(*renderer_);
         }
         return (dataset_.size());
     }
 private:
     const vector<T>& dataset_;
-    MessageRenderer renderer_;
+    // Just-in-time initialized pointer, so no copy
+    MessageRenderer* renderer_;
 };
 
 // This supplemental class emulates an RRset like class that internally

src/lib/dns/messagerenderer.h

@@ -17,6 +17,8 @@
 
 #include <util/buffer.h>
 
+#include <boost/noncopyable.hpp>
+
 namespace isc {
 
 namespace dns {
@@ -346,7 +348,8 @@ public:
 /// end of the buffer at the time of construction.  However, if the
 /// pre-existing portion of the buffer contains DNS names, these names won't
 /// be considered for name compression.
-class MessageRenderer : public AbstractMessageRenderer {
+class MessageRenderer : public AbstractMessageRenderer,
+    public boost::noncopyable { // Can crash if copied
 public:
     using AbstractMessageRenderer::CASE_INSENSITIVE;
     using AbstractMessageRenderer::CASE_SENSITIVE;