--- a/langtools/make/Makefile	Wed Jul 05 16:51:35 2017 +0200
+++ b/langtools/make/Makefile	Fri Apr 17 15:56:31 2009 +0100
@@ -105,6 +105,14 @@
   endif
 endif
 
+ifeq ($(DEBUG_CLASSFILES), true)
+  ANT_OPTIONS += -Djavac.debug=true
+  ANT_OPTIONS += -Djavac.debuglevel=source,lines,vars
+else
+  ANT_OPTIONS += -Djavac.debug=false
+  ANT_OPTIONS += -Djavac.debuglevel=
+endif
+
 # Note: jdk/make/common/Defs.gmk uses LANGUAGE_VERSION (-source NN)
 # and the somewhat misnamed CLASS_VERSION (-target NN)
 ifdef TARGET_CLASS_VERSION