Trent Mick points out that the BSD DB also provides an ndbm compatibility

layer.  If that is available, consider that as an option as well.

Modules/dbmmodule.c

@@ -13,6 +13,8 @@
  */
 #if defined(HAVE_NDBM_H)
 #include <ndbm.h>
+#elif defined(HAVE_DB1_NDBM_H)
+#include <db1/ndbm.h>
 #elif defined(HAVE_GDBM_NDBM_H)
 #include <gdbm/ndbm.h>
 #else

config.h.in

@@ -524,6 +524,9 @@
 /* Define if you have the <db_185.h> header file.  */
 #undef HAVE_DB_185_H
 
+/* Define if you have the <db1/ndbm.h> header file.  */
+#undef HAVE_DB1_NDBM_H
+
 /* Define if you have the <db.h> header file.  */
 #undef HAVE_DB_H
 

configure.in

@@ -371,7 +371,8 @@ AC_CHECK_HEADERS(dlfcn.h fcntl.h limits.h locale.h ncurses.h poll.h pthread.h \
 signal.h stdarg.h stddef.h stdlib.h thread.h unistd.h utime.h \
 sys/audioio.h sys/file.h sys/lock.h db_185.h db.h \
 sys/param.h sys/select.h sys/socket.h sys/time.h sys/times.h \
-sys/un.h sys/utsname.h sys/wait.h pty.h libutil.h ndbm.h gdbm/ndbm.h)
+sys/un.h sys/utsname.h sys/wait.h pty.h libutil.h \
+ndbm.h db1/ndbm.h gdbm/ndbm.h)
 AC_HEADER_DIRENT
 
 # checks for typedefs