diff -ruN -x strclass.h ddd-3.3.12/ddd/Makefile.am my/ddd/Makefile.am
--- ddd-3.3.12/ddd/Makefile.am	2009-02-11 18:25:07.000000000 +0100
+++ my/ddd/Makefile.am	2019-11-22 22:49:26.212765331 +0100
@@ -580,9 +580,8 @@
 
 # Make sure needed headers are built before trying to compile these files
 # (Assume ddd.C is the first source file to be built.)
-ddd.o: version.h host.h root.h
-resources.o: Ddd.ad.h
-show.o: build.h
+# MM: AND WHY WOULD YOU ASSUME THAT??
+BUILT_SOURCES = version.h host.h root.h Ddd.ad.h build.h
 
 # -----------------------------------------------------------------------------
 # Local Libraries.