not sure, but I believe back-hdb needs monitor.c as well...

servers/slapd/back-hdb/Makefile.in

@@ -21,13 +21,15 @@ XXSRCS = init.c tools.c config.c \
 	add.c bind.c compare.c delete.c modify.c modrdn.c search.c \
 	extended.c referral.c operational.c \
 	attr.c index.c key.c dbcache.c filterindex.c trans.c \
-	dn2entry.c dn2id.c error.c id2entry.c idl.c nextid.c cache.c
+	dn2entry.c dn2id.c error.c id2entry.c idl.c nextid.c cache.c \
+	monitor.c
 SRCS = $(XXSRCS)
 OBJS = init.lo tools.lo config.lo \
 	add.lo bind.lo compare.lo delete.lo modify.lo modrdn.lo search.lo \
 	extended.lo referral.lo operational.lo \
 	attr.lo index.lo key.lo dbcache.lo filterindex.lo trans.lo \
-	dn2entry.lo dn2id.lo error.lo id2entry.lo idl.lo nextid.lo cache.lo
+	dn2entry.lo dn2id.lo error.lo id2entry.lo idl.lo nextid.lo cache.lo \
+	monitor.lo
 
 LDAP_INCDIR= ../../../include       
 LDAP_LIBDIR= ../../../libraries