+## Define MAIL_USE_FLOCK (or LOCKF) if the mailer uses flock (or lockf) to
+## interlock access to the mail spool. The alternative is a lock file named
+## /usr/spool/mail/$USER.lock.
+mail_lock=no
+case "$opsys" in
+ aix4-2) mail_lock="lockf" ;;
+
+ gnu|freebsd|netbsd|openbsd|darwin|irix6-5) mail_lock="flock" ;;
+
+ ## On GNU/Linux systems, both methods are used by various mail programs.
+ ## I assume most people are using newer mailers that have heard of flock.
+ ## Change this if you need to.
+ ## Debian contains a patch which says: ``On Debian/GNU/Linux systems,
+ ## configure gets the right answers, and that means *NOT* using flock.
+ ## Using flock is guaranteed to be the wrong thing. See Debian Policy
+ ## for details.'' and then uses `#ifdef DEBIAN'. Unfortunately the
+ ## Debian maintainer hasn't provided a clean fix for Emacs.
+ ## movemail.c will use `maillock' when MAILDIR, HAVE_LIBMAIL and
+ ## HAVE_MAILLOCK_H are defined, so the following appears to be the
+ ## correct logic. -- fx
+ ## We must check for HAVE_LIBLOCKFILE too, as movemail does.
+ ## liblockfile is a Free Software replacement for libmail, used on
+ ## Debian systems and elsewhere. -rfr.
+ gnu-*)
+ mail_lock="flock"
+ if test $have_mail = yes || test $have_lockfile = yes; then
+ test $ac_cv_header_maillock_h = yes && mail_lock=no
+ fi
+ ;;
+esac
+
+BLESSMAIL_TARGET=
+case "$mail_lock" in
+ flock) AC_DEFINE(MAIL_USE_FLOCK, 1, [Define if the mailer uses flock to interlock the mail spool.]) ;;
+
+ lockf) AC_DEFINE(MAIL_USE_LOCKF, 1, [Define if the mailer uses lockf to interlock the mail spool.]) ;;
+
+ *) BLESSMAIL_TARGET="need-blessmail" ;;
+esac
+AC_SUBST(BLESSMAIL_TARGET)
+
+