+# Activate the warnings on #if FOOBAR when FOOBAR has no value
+# It breaks on FreeBSD within Boost headers, so activate this only in Pure Hardcore debug mode.
+if(enable_maintainer_mode)
+ set(warnCFLAGS "${warnCFLAGS} -Wundef")
+ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wundef")
+endif()
+