[gimp] libgimp: make sure the GimpPlugIn and GimpPDB singletons get destroyed

[Michael Natterer <mitch src gnome org>]

commit b587740a101c588794237292c3f6a25c431612c0
Author: Michael Natterer <mitch gimp org>
Date:   Mon Sep 9 11:16:39 2019 +0200

    libgimp: make sure the GimpPlugIn and GimpPDB singletons get destroyed
    
    Break reference cycles between the objects and the procedures they
    keep by moving procedure destruction to dispose() and calling
    g_object_run_dispose() before unrefing PLUG_IN and PDB in gimp.c.
    
    Also some formatting and "Since: 3.0" annotation .

 libgimp/gimp.c       | 12 ++++++++++--
 libgimp/gimp.h       |  2 ++
 libgimp/gimppdb.c    | 17 ++++++++++++++---
 libgimp/gimpplugin.c | 40 +++++++++++++++++++++++++---------------
 4 files changed, 51 insertions(+), 20 deletions(-)
---
diff --git a/libgimp/gimp.c b/libgimp/gimp.c
index 045c7c734d..fa9920fc79 100644
--- a/libgimp/gimp.c
+++ b/libgimp/gimp.c
@@ -167,8 +167,12 @@ static GimpStackTraceMode  stack_trace_mode  = GIMP_STACK_TRACE_NEVER;
  * #GimpPlugIn subclass type and the 'argc' and 'argv' that are passed
  * to "main".
  *
+ * See also: GIMP_MAIN().
+ *
  * Returns: an exit status as defined by the C library,
  *          on success EXIT_SUCCESS.
+ *
+ * Since: 3.0
  **/
 gint
 gimp_main (GType  plug_in_type,
@@ -597,7 +601,7 @@ gimp_main (GType  plug_in_type,
  * This function returns the plug-in's #GimpPlugIn instance, which can
  * exist exactly once per running plug-in program.
  *
- * Returns: (transfer none) (nullable): The plug-in's #GimpPlugIn singleton, or %NULL.
+ * Returns: (transfer none) (nullable): The plug-in's #GimpPlugIn singleton.
  *
  * Since: 3.0
  **/
@@ -613,7 +617,7 @@ gimp_get_plug_in (void)
  * This function returns the plug-in's #GimpPDB instance, which can
  * exist exactly once per running plug-in program.
  *
- * Returns: (transfer none) (nullable): The plug-in's #GimpPDB singleton, or %NULL.
+ * Returns: (transfer none) (nullable): The plug-in's #GimpPDB singleton.
  *
  * Since: 3.0
  **/
@@ -918,7 +922,11 @@ gimp_close (void)
 
   _gimp_plug_in_quit (PLUG_IN);
 
+  if (PDB)
+    g_object_run_dispose (G_OBJECT (PDB));
   g_clear_object (&PDB);
+
+  g_object_run_dispose (G_OBJECT (PLUG_IN));
   g_clear_object (&PLUG_IN);
 }
 
diff --git a/libgimp/gimp.h b/libgimp/gimp.h
index 7dd69be50b..7d51623871 100644
--- a/libgimp/gimp.h
+++ b/libgimp/gimp.h
@@ -89,6 +89,8 @@ G_BEGIN_DECLS
  * GIMP_MAIN (MY_TYPE_PLUG_IN)
  *
  * at the toplevel of your file. No semicolon should be used.
+ *
+ * Since: 3.0
  **/
 
 #ifdef G_OS_WIN32
diff --git a/libgimp/gimppdb.c b/libgimp/gimppdb.c
index 0925741ba5..6f665a4987 100644
--- a/libgimp/gimppdb.c
+++ b/libgimp/gimppdb.c
@@ -48,15 +48,16 @@
 
 struct _GimpPDBPrivate
 {
-  GimpPlugIn *plug_in;
+  GimpPlugIn         *plug_in;
 
-  GHashTable *procedures;
+  GHashTable         *procedures;
 
   GimpPDBStatusType   error_status;
   gchar              *error_message;
 };
 
 
+static void   gimp_pdb_dispose   (GObject        *object);
 static void   gimp_pdb_finalize  (GObject        *object);
 
 static void   gimp_pdb_set_error (GimpPDB        *pdb,
@@ -73,6 +74,7 @@ gimp_pdb_class_init (GimpPDBClass *klass)
 {
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
+  object_class->dispose  = gimp_pdb_dispose;
   object_class->finalize = gimp_pdb_finalize;
 }
 
@@ -87,13 +89,22 @@ gimp_pdb_init (GimpPDB *pdb)
   pdb->priv->error_status = GIMP_PDB_SUCCESS;
 }
 
+static void
+gimp_pdb_dispose (GObject *object)
+{
+  GimpPDB *pdb = GIMP_PDB (object);
+
+  g_clear_pointer (&pdb->priv->procedures, g_hash_table_unref);
+
+  G_OBJECT_CLASS (parent_class)->dispose (object);
+}
+
 static void
 gimp_pdb_finalize (GObject *object)
 {
   GimpPDB *pdb = GIMP_PDB (object);
 
   g_clear_object (&pdb->priv->plug_in);
-  g_clear_pointer (&pdb->priv->procedures,    g_hash_table_unref);
   g_clear_pointer (&pdb->priv->error_message, g_free);
 
   G_OBJECT_CLASS (parent_class)->finalize (object);
diff --git a/libgimp/gimpplugin.c b/libgimp/gimpplugin.c
index 6ccddc74ee..10665f9fb8 100644
--- a/libgimp/gimpplugin.c
+++ b/libgimp/gimpplugin.c
@@ -96,19 +96,20 @@ struct _GimpPlugInPrivate
 };
 
 
-static void       gimp_plug_in_constructed       (GObject      *object);
-static void       gimp_plug_in_finalize          (GObject      *object);
-static void       gimp_plug_in_set_property      (GObject      *object,
-                                                  guint         property_id,
-                                                  const GValue *value,
-                                                  GParamSpec   *pspec);
-static void       gimp_plug_in_get_property      (GObject      *object,
-                                                  guint         property_id,
-                                                  GValue       *value,
-                                                  GParamSpec   *pspec);
-
-static void       gimp_plug_in_register          (GimpPlugIn   *plug_in,
-                                                  GList        *procedures);
+static void       gimp_plug_in_constructed       (GObject         *object);
+static void       gimp_plug_in_dispose           (GObject         *object);
+static void       gimp_plug_in_finalize          (GObject         *object);
+static void       gimp_plug_in_set_property      (GObject         *object,
+                                                  guint            property_id,
+                                                  const GValue    *value,
+                                                  GParamSpec      *pspec);
+static void       gimp_plug_in_get_property      (GObject         *object,
+                                                  guint            property_id,
+                                                  GValue          *value,
+                                                  GParamSpec      *pspec);
+
+static void       gimp_plug_in_register          (GimpPlugIn      *plug_in,
+                                                  GList           *procedures);
 
 static gboolean   gimp_plug_in_write             (GIOChannel      *channel,
                                                   const guint8    *buf,
@@ -158,6 +159,7 @@ gimp_plug_in_class_init (GimpPlugInClass *klass)
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
   object_class->constructed  = gimp_plug_in_constructed;
+  object_class->dispose      = gimp_plug_in_dispose;
   object_class->finalize     = gimp_plug_in_finalize;
   object_class->set_property = gimp_plug_in_set_property;
   object_class->get_property = gimp_plug_in_get_property;
@@ -204,10 +206,9 @@ gimp_plug_in_constructed (GObject *object)
 }
 
 static void
-gimp_plug_in_finalize (GObject *object)
+gimp_plug_in_dispose (GObject *object)
 {
   GimpPlugIn *plug_in = GIMP_PLUG_IN (object);
-  GList      *list;
 
   if (plug_in->priv->extension_source_id)
     {
@@ -221,6 +222,15 @@ gimp_plug_in_finalize (GObject *object)
       plug_in->priv->temp_procedures = NULL;
     }
 
+  G_OBJECT_CLASS (parent_class)->dispose (object);
+}
+
+static void
+gimp_plug_in_finalize (GObject *object)
+{
+  GimpPlugIn *plug_in = GIMP_PLUG_IN (object);
+  GList      *list;
+
   g_clear_pointer (&plug_in->priv->translation_domain_name, g_free);
   g_clear_object  (&plug_in->priv->translation_domain_path);