-dnl Note that unless support for DB/(G)DBM is explicitly disabled, we always
-dnl want to check for libdb/lib(g)dbm. Also note that libc will not be
-dnl checked if we have the libraries.
-dnl If support for DB/(G)DBM is requested, but we neither have libdb/lib(g)dbm,
-dnl nor does libc implement it, we are a bit lost :)
-
-AC_CHECKING(for database support)
+dnl By default, we check for DBM support in libgdbm, then libc, then libdbm.
+
+test "$with_database_gnudbm $with_database_dbm $with_database_berkdb" \
+ != "no no no" && AC_CHECKING(for database support)
+
+dnl Check for ndbm.h, required for either kind of DBM support.
+if test "$with_database_gnudbm $with_database_dbm" != "no no"; then
+ AC_CHECK_HEADER(ndbm.h, [:], [
+ test "$with_database_gnudbm" = "yes" -o \
+ "$with_database_dbm" = "yes" && \
+ XE_DIE("Required DBM support cannot be provided.")
+ with_database_gnudbm=no with_database_dbm=no])
+fi