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, 19 insertions, 2 deletions

diff --git a/man/sd_event_source_unref.xml b/man/sd_event_source_unref.xml
index 579ec47e8e..2c4d450763 100644
--- a/man/sd_event_source_unref.xml
+++ b/man/sd_event_source_unref.xml
@@ -44,6 +44,7 @@
 
   <refnamediv>
     <refname>sd_event_source_unref</refname>
+    <refname>sd_event_source_unrefp</refname>
     <refname>sd_event_source_ref</refname>
 
     <refpurpose>Increase or decrease event source reference counters</refpurpose>
@@ -59,6 +60,11 @@
       </funcprototype>
 
       <funcprototype>
+        <funcdef>void <function>sd_event_source_unrefp</function></funcdef>
+        <paramdef>sd_event_source **<parameter>source</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
         <funcdef>sd_event_source* <function>sd_event_source_ref</function></funcdef>
         <paramdef>sd_event_source *<parameter>source</parameter></paramdef>
       </funcprototype>
@@ -80,12 +86,23 @@
     the reference counter reaches zero it is removed from its event loop
     object and destroyed.</para>
 
+    <para><function>sd_event_source_unrefp()</function> is similar to
+    <function>sd_event_source_unref()</function> but takes a pointer to a
+    pointer to an <type>sd_event_source</type> object. This call is useful in
+    conjunction with GCC's and LLVM's <ulink
+    url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
+    Variable Attribute</ulink>. Note that this function is defined as
+    inline function.</para>
+
     <para><function>sd_event_source_ref()</function> may be used
     to increase by one the reference counter of the event source object
     specified as <parameter>source</parameter>.</para>
 
-    <para>Both functions execute no operation if the passed event
-    source object is <constant>NULL</constant>.</para>
+    <para><function>sd_event_source_unref()</function>,
+    <function>sd_bus_creds_unrefp()</function> and
+    <function>sd_bus_creds_ref()</function> execute no operation if
+    the passed event source object is
+    <constant>NULL</constant>.</para>
 
     <para>Note that event source objects stay alive and may be
     dispatched as long as they have a reference counter greater than