suppress boost warning fix ospray one

two buildbot warnings

CMake/CTestCustom.cmake.in

@@ -69,7 +69,10 @@ if (NOT cdash_show_third_party_warnings)
     # and causes a match due to the work warning in it
     "return 0;       /\\* supresses a warning \\*/"
 
-
+    # boost graph lib causes a warning on gcc with code that
+    # boost uses internally. An example for you template fans is
+    # /source/Infovis/BoostGraphAlgorithms/Testing/Cxx/TestBoostAdapter.cxx:221:47: warning: '*((void*)(& ei)+32).__gnu_cxx::__normal_iterator<boost::detail::stored_edge_property<long unsigned int, boost::property<boost::edge_index_t, unsigned int> >*, std::vector<boost::detail::stored_edge_property<long unsigned int, boost::property<boost::edge_index_t, unsigned int> >, std::allocator<boost::detail::stored_edge_property<long unsigned int, boost::property<boost::edge_index_t, unsigned int> > > > >::_M_current' may be used uninitialized in this function [-Wmaybe-uninitialized]
+    "[Bb]oost[Gg]raph.*edge_property.*may be used uninitialized"
   )
 endif ()
 

Rendering/OSPRay/vtkOSPRayMaterialLibrary.cxx

@@ -527,13 +527,24 @@ const char * vtkOSPRayMaterialLibrary::WriteBuffer()
   }
 
   root["materials"] = materials;
-  Json::FastWriter fast;
-  std::string sFast = fast.write(root);
 
-  char *buf = new char[sFast.length()+1];
-  memcpy(buf, sFast.c_str(), sFast.length());
-  buf[sFast.length()] =0;
-  return buf;
+  Json::StreamWriterBuilder builder;
+  builder["commentStyle"] = "None";
+  builder["indentation"] = "   ";
+  std::unique_ptr<Json::StreamWriter> writer(
+      builder.newStreamWriter());
+  std::ostringstream result;
+  writer->write(root, &result);
+  std::string rstring = result.str();
+
+  if (rstring.size())
+  {
+    char *buf = new char[rstring.size()+1];
+    memcpy(buf, rstring.c_str(), rstring.size());
+    buf[rstring.size()] = 0;
+    return buf;
+  }
+  return nullptr;
 }
 
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