--- a/src/internet/model/rtt-estimator.cc	Thu Mar 05 15:50:18 2015 +0100
+++ b/src/internet/model/rtt-estimator.cc	Wed Mar 11 16:50:35 2015 +0100
@@ -170,23 +170,23 @@
       return 0;
     }
   // supports 1/32, 1/16, 1/8, 1/4, 1/2
-  if (abs (1/val - 8) < TOLERANCE)
+  if (std::abs (1/val - 8) < TOLERANCE)
     {
       return 3;
     }
-  if (abs (1/val - 4) < TOLERANCE)
+  if (std::abs (1/val - 4) < TOLERANCE)
     {
       return 2;
     }
-  if (abs (1/val - 32) < TOLERANCE)
+  if (std::abs (1/val - 32) < TOLERANCE)
     {
       return 5;
     }
-  if (abs (1/val - 16) < TOLERANCE)
+  if (std::abs (1/val - 16) < TOLERANCE)
     {
       return 4;
     }
-  if (abs (1/val - 2) < TOLERANCE)
+  if (std::abs (1/val - 2) < TOLERANCE)
     {
       return 1;
     }

--- a/src/wave/helper/wave-helper.cc	Thu Mar 05 15:50:18 2015 +0100
+++ b/src/wave/helper/wave-helper.cc	Wed Mar 11 16:50:35 2015 +0100
@@ -27,6 +27,7 @@
 #include "ns3/wave-net-device.h"
 #include "ns3/minstrel-wifi-manager.h"
 #include "ns3/radiotap-header.h"
+#include "ns3/unused.h"
 #include "wave-mac-helper.h"
 #include "wave-helper.h"
 
@@ -484,12 +485,7 @@
   try
     {
       const QosWaveMacHelper& qosMac = dynamic_cast<const QosWaveMacHelper&> (macHelper);
-      // below check will never fail, just used for survive from
-      // gcc warn "-Wunused-but-set-variable"
-      if (&qosMac == 0)
-        {
-          NS_FATAL_ERROR ("it could never get here");
-        }
+      NS_UNUSED (qosMac);
     }
   catch (const std::bad_cast &)
     {