Replace NULL by nullptr

src/OpenMesh/Tools/Utils/Gnuplot.cc

@@ -38,7 +38,7 @@
 #  define access _access
 #  define ACCESS_OK 0
 #  define PATH_SEP ";"
-#  define MKTEMP_AND_CHECK_FAILED(name) (_mktemp(name) == NULL)
+#  define MKTEMP_AND_CHECK_FAILED(name) (_mktemp(name) == nullptr)
 #else
 #  define ACCESS_OK X_OK
 #  define PATH_SEP ":"
@@ -368,7 +368,7 @@ void Gnuplot::plot_x(vector<double> d, const string &title)
   //
   //open temporary files for output
 #ifdef WIN32
-  if ( _mktemp(name) == NULL)
+  if ( _mktemp(name) == nullptr)
 #else
   if ( mkstemp(name) == -1 )
 #endif

src/OpenMesh/Tools/Utils/conio.cc

@@ -120,7 +120,7 @@ int kbhit(void)
     error += tcsetattr(0, TCSANOW, &Otty);
     tv.tv_sec = 0;
     tv.tv_usec = 100; /* insert at least a minimal delay */
-    select(1, NULL, NULL, NULL, &tv);
+    select(1, nullptr, nullptr, nullptr, &tv);
   }
   return (error == 0 ? cnt : -1 );
 }