check_users: prefer systemd-logind over utmprefs/pull/1888/head

Prefer systemd-logind over utmp to get the number of logged in users.
utmp is not reliable for this (e.g. some terminals create utmp entries,
other not) and utmp is not Y2038 safe with glibc on Linux.

1 files changed, 19 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 069cc62..a294b00 100644
--- a/configure.ac
+++ b/configure.ac
@@ -328,6 +328,25 @@ AS_IF([test "x$with_ldap" != "xno"], [
   LIBS="$_SAVEDLIBS"
 ])
 
+
+AC_ARG_WITH([systemd], [AS_HELP_STRING([--without-systemd], [Skips systemd support])])
+
+dnl Check for libsystemd
+AS_IF([test "x$with_systemd" != "xno"], [
+  _SAVEDLIBS="$LIBS"
+  AC_CHECK_LIB(systemd,sd_get_sessions,,,-lsystemd)
+  if test "$ac_cv_lib_systemd_sd_get_sessions" = "yes"; then
+    SYSTEMDLIBS="-lsystemd"
+    SYSTEMDINCLUDE=""
+    AC_SUBST(SYSTEMDLIBS)
+    AC_SUBST(SYSTEMDINCLUDE)
+  else
+    AC_MSG_WARN([Skipping systemd support])
+  fi
+  LIBS="$_SAVEDLIBS"
+])
+
+
 dnl Check for headers used by check_ide_smart
 case $host in
   *linux*)