From FrancoisTigeot, "OpenSceneGraph 3.0.1 doesn't build out of the box on DragonFly and needs

a few modifications to these files:
  - applications/present3D/Cluster.cpp
  - src/osgDB/FileUtils.cpp

The changes are needed to fix a few platform specific things such as the
absence of stat64, int/socklen_t differences, etc... and are in the same
line as Linux, Apple and FreeBSD specific checks.

I have attached the modified files; the original patches to 3.0.1 are
also visible here if you find it more convenient:
http://dl.wolfpond.org/dports/graphics.osg/dragonfly/patch-applications_present3D_Cluster.cpp
http://dl.wolfpond.org/dports/graphics.osg/dragonfly/patch-src_osgDB_FileUtils.cpp

With these changes, osg 3.0.1 is able to be built and packaged on DragonFly
whereas it previously failed to compile."

src/osgDB/FileUtils.cpp

@@ -76,7 +76,8 @@ typedef char TCHAR;
     #if (MAC_OS_X_VERSION_MAX_ALLOWED <= 1040)
         #define stat64 stat
     #endif
-#elif defined(__CYGWIN__) || defined(__FreeBSD__) || (defined(__hpux) && !defined(_LARGEFILE64_SOURCE))
+#elif defined(__CYGWIN__) || defined(__FreeBSD__) || defined(__DragonFly__) || \
+      (defined(__hpux) && !defined(_LARGEFILE64_SOURCE))
     #define stat64 stat
 #endif