test-login: make the test non-manual

test-login.c is largely rewritten to use _cleanup_ and give more meaningful
messages (function names are used instead of creative terms like "active
session", so that when something unexpected is returned, it's much easier to
see what function is responsible).

The monitoring part is only activated if '-m' is passed on the command line.

It runs against the information from /run/systemd/ in the live system, but that
should be OK: logind/sd-login interface is supposed to be stable and both
backwards and forwards compatible.

If not running in a login session, some tests are skipped.

Those two changes together mean that it's possible to run test-login in the
test suite.

Tests for sd_pid_get_{unit,user_unit,slice} are added.

2 files changed, 7 insertions, 6 deletions

diff --git a/man/sd_pid_get_session.xml b/man/sd_pid_get_session.xml
index 806cff34e4..0c135ba871 100644
--- a/man/sd_pid_get_session.xml
+++ b/man/sd_pid_get_session.xml
@@ -177,7 +177,7 @@
     processes, user processes that are shared between multiple
     sessions of the same user, or kernel threads). For processes not
     being part of a login session, this function will fail with
-    -ENODATA. The returned string needs to be freed with the libc
+    <constant>-ENODATA</constant>. The returned string needs to be freed with the libc
     <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     call after use.</para>
@@ -189,7 +189,7 @@
     paths. Note that not all processes are part of a system
     unit/service (e.g. user processes, or kernel threads). For
     processes not being part of a systemd system unit, this function
-    will fail with -ENODATA. (More specifically, this call will not
+    will fail with <constant>-ENODATA</constant>. (More specifically, this call will not
     work for kernel threads.) The returned string needs to be freed
     with the libc <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
@@ -208,7 +208,7 @@
     multiple login sessions of the same user, whereas
     <function>sd_pid_get_session()</function> will fail. For processes
     not being part of a login session and not being a shared process
-    of a user, this function will fail with -ENODATA.</para>
+    of a user, this function will fail with <constant>-ENODATA</constant>.</para>
 
     <para><function>sd_pid_get_machine_name()</function> may be used
     to determine the name of the VM or container is a member of. The
@@ -217,7 +217,7 @@
     <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     call after use. For processes not part of a VM or containers, this
-    function fails with -ENODATA.</para>
+    function fails with <constant>-ENODATA</constant>.</para>
 
     <para><function>sd_pid_get_slice()</function> may be used to
     determine the slice unit the process is a member of. See
diff --git a/man/sd_session_is_active.xml b/man/sd_session_is_active.xml
index a6076b177a..f95e74ead6 100644
--- a/man/sd_session_is_active.xml
+++ b/man/sd_session_is_active.xml
@@ -184,8 +184,9 @@
     <para><function>sd_session_get_seat()</function> may be used to
     determine the seat identifier of the seat the session identified
     by the specified session identifier belongs to. Note that not all
-    sessions are attached to a seat, this call will fail for them. The
-    returned string needs to be freed with the libc
+    sessions are attached to a seat, this call will fail (returning
+    <constant>-ENODATA</constant>) for them. The returned string needs
+    to be freed with the libc
     <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     call after use.</para>