tree-wide: expose "p"-suffix unref calls in public APIs to make gcc cleanup easy

GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.

With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.

The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).

This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.

Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:

       #define _cleanup_(function) __attribute__((cleanup(function)))

Or similar, to make the gcc feature easier to use.

Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.

See #2008.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/libelogind/sd-bus/bus-track.c b/src/libelogind/sd-bus/bus-track.c
index 5f6e0f8cc..5cd3af3b3 100644
--- a/src/libelogind/sd-bus/bus-track.c
+++ b/src/libelogind/sd-bus/bus-track.c
@@ -112,7 +112,9 @@ _public_ int sd_bus_track_new(
 }
 
 _public_ sd_bus_track* sd_bus_track_ref(sd_bus_track *track) {
-        assert_return(track, NULL);
+
+        if (!track)
+                return NULL;
 
         assert(track->n_ref > 0);
 
@@ -162,7 +164,7 @@ static int on_name_owner_changed(sd_bus_message *message, void *userdata, sd_bus
 }
 
 _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
-        _cleanup_bus_slot_unref_ sd_bus_slot *slot = NULL;
+        _cleanup_(sd_bus_slot_unrefp) sd_bus_slot *slot = NULL;
         _cleanup_free_ char *n = NULL;
         const char *match;
         int r;
@@ -208,7 +210,7 @@ _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
 }
 
 _public_ int sd_bus_track_remove_name(sd_bus_track *track, const char *name) {
-        _cleanup_bus_slot_unref_ sd_bus_slot *slot = NULL;
+        _cleanup_(sd_bus_slot_unrefp) sd_bus_slot *slot = NULL;
         _cleanup_free_ char *n = NULL;
 
         assert_return(name, -EINVAL);